Every extra sale can bring an extra bill with it.
Sell one more product?
You may need one more unit of stock.
One more package.
One more transaction fee.
One more delivery.
One more sales commission.
Revenue goes up.
But some costs move with it.
Those are variable costs.
Variable costs rise and fall with the level of business activity.
They are the costs that follow the sale, the order, the job, the booking or the unit produced.
That is why “we sold more” is never the full story.
The better question is:
How much did each extra sale leave behind after the costs that moved with it?
Belvara view: More sales can grow revenue and grow costs at the same time. The part that matters is what each extra sale still contributes after the variable cost follows it.
What are variable costs?
Variable costs are costs that change as the level of sales, production or business activity changes.
If activity increases, total variable costs usually increase.
If activity falls, total variable costs usually fall.
Common examples can include:
- product cost
- raw materials
- packaging per order
- transaction fees charged per sale
- sales commissions
- marketplace commissions
- delivery costs linked to individual orders
- direct labour that changes with production or jobs
- payment-processing fees
- usage-based software charges
The exact classification depends on the business and the nature of the cost.
A cost should not be called variable simply because the amount changes from month to month.
The important question is:
Does the cost move because the level of activity moved?
A simple variable-cost example
Suppose you sell a product for:
KES 2,000
Variable costs per sale are:
- Product cost: KES 1,000
- Packaging: KES 100
- Transaction fee: KES 40
- Delivery subsidy: KES 160
Total variable cost per sale:
KES 1,300
Contribution per sale:
KES 2,000 − KES 1,300 = KES 700
Sell one unit:
Variable cost:
KES 1,300
Sell 100 units:
Variable cost:
KES 130,000
Sell 500 units:
Variable cost:
KES 650,000
The cost grows because activity grows.
That is variable-cost behaviour.
Variable costs vs fixed costs
This is the basic distinction.
Variable costs change with activity.
Fixed costs do not usually change directly with each additional sale in the short term.
Suppose a business has:
- Product cost per unit: KES 1,000
- Packaging per order: KES 100
- Transaction fee per sale: KES 40
- Monthly rent: KES 80,000
- Salaried admin payroll: KES 120,000
If sales double:
- Product cost usually rises
- Packaging usually rises
- Transaction fees usually rise
But rent may stay the same.
Salaried admin payroll may stay the same.
| Cost | Behaviour when sales rise | Typical classification |
| Product cost | Usually rises | Variable |
| Packaging per order | Usually rises | Variable |
| Transaction fee | Usually rises | Variable |
| Rent | Usually stays the same short term | Fixed |
| Salaried admin payroll | Usually stays the same short term | Fixed |
The distinction matters because break-even, contribution margin and forecasting depend on it.
Fixed costs tell you what the business carries. Variable costs tell you what each extra sale brings with it.
Variable cost per unit
Variable cost can be measured per unit.
Suppose:
- Product cost: KES 800
- Packaging: KES 100
- Sales commission: KES 50
Variable cost per unit:
KES 950
If the selling price is:
KES 1,500
Contribution per unit:
KES 550
That KES 550 contributes towards fixed costs and then profit.
This is why variable cost is central to contribution margin.
Total variable cost
Total variable cost is:
Variable Cost per Unit × Number of Units
Suppose:
- Variable cost per unit: KES 950
- Units sold: 400
Total variable cost:
KES 950 × 400 = KES 380,000
If units sold increase to 600:
KES 950 × 600 = KES 570,000
Total variable cost rises with activity.
Variable costs and contribution margin
Contribution margin is what remains after variable costs are deducted from revenue.
For a single unit:
Contribution Margin per Unit = Selling Price − Variable Cost per Unit
Suppose:
- Selling price: KES 2,500
- Variable cost: KES 1,500
Contribution per unit:
KES 1,000
That KES 1,000 is not automatically final profit.
It still has to help cover fixed costs.
After fixed costs are covered, additional contribution can begin to create operating profit.
Belvara view: Revenue tells you what the customer paid. Contribution tells you what the sale left behind to help carry the business.
Variable cost percentage
A business can also express variable cost as a percentage of revenue.
Suppose:
- Selling price: KES 2,000
- Variable cost: KES 1,200
Variable cost percentage:
KES 1,200 ÷ KES 2,000 × 100 = 60%
Contribution margin ratio:
40%
This means 60% of each sales shilling is absorbed by variable cost before fixed costs are considered.
That leaves 40% to cover fixed costs and then profit.
Why variable costs matter
Variable costs decide how much each additional sale is worth.
Two products can have the same selling price and completely different economics.
Product A
- Selling price: KES 2,000
- Variable cost: KES 1,000
- Contribution: KES 1,000
Product B
- Selling price: KES 2,000
- Variable cost: KES 1,600
- Contribution: KES 400
Revenue per sale is identical.
But Product A leaves KES 1,000.
Product B leaves KES 400.
The sales report says both products made KES 2,000.
Variable cost tells you why those sales are not equally valuable.
More sales can create more cost faster than expected
Suppose a business sells 100 units.
Selling price:
KES 2,000
Variable cost:
KES 1,200
Revenue:
KES 200,000
Variable cost:
KES 120,000
Contribution:
KES 80,000
Now sales double to 200 units.
Revenue becomes:
KES 400,000
Variable cost becomes:
KES 240,000
Contribution becomes:
KES 160,000
That is healthy if the economics stay stable.
But now imagine the extra volume requires:
- express restocking
- higher delivery subsidies
- overtime
- marketplace commissions
- promotional discounts
Variable cost per sale rises from:
KES 1,200
to:
KES 1,500
At 200 units:
Revenue:
KES 400,000
Variable cost:
KES 300,000
Contribution:
KES 100,000
Sales doubled.
Contribution increased by only KES 20,000.
Growth is weaker when every extra sale becomes more expensive to fulfil.
Discounts can make variable costs feel heavier
Suppose:
- Selling price: KES 2,000
- Variable cost: KES 1,200
- Contribution: KES 800
Now offer a 20% discount.
New selling price:
KES 1,600
Variable cost stays:
KES 1,200
Contribution falls to:
KES 400
The variable cost did not increase.
But it now consumes:
75% of revenue
instead of:
60%
The same KES 1,200 cost became much heavier relative to the sale.
This is why discounting can destroy contribution quickly.
A discount does not ask your supplier to lower the cost just because you lowered the price.
Supplier price increases raise variable cost directly
Suppose:
- Selling price: KES 2,000
- Product cost: KES 1,000
- Other variable costs: KES 200
- Total variable cost: KES 1,200
- Contribution: KES 800
Now supplier cost rises to:
KES 1,200
New total variable cost:
KES 1,400
New contribution:
KES 600
Contribution per sale falls by:
25%
The customer sees the same KES 2,000 price.
The sales report may look normal.
The sale quietly became less valuable.
Delivery can become a variable cost problem
Delivery often looks small when viewed order by order.
Suppose:
- Product selling price: KES 3,000
- Product and other variable costs: KES 1,700
- Contribution before delivery: KES 1,300
The business subsidises delivery by:
KES 400
Contribution falls to:
KES 900
Sell 1,000 orders and the delivery subsidy totals:
KES 400,000
A cost that feels small per order can become one of the largest variable-cost lines at scale.
Payment fees scale with revenue
Suppose a payment provider charges:
2% per transaction
If monthly processed sales are:
KES 500,000
Fees:
KES 10,000
At:
KES 5,000,000
Fees:
KES 100,000
At:
KES 20,000,000
Fees:
KES 400,000
The fee percentage did not change.
The cost grew because the business grew.
Small percentages stop feeling small when they sit on top of large revenue.
Packaging is easy to ignore until volume grows
Suppose packaging costs:
KES 80 per order
At 100 orders:
KES 8,000
At 1,000 orders:
KES 80,000
At 10,000 orders:
KES 800,000
The business may think of packaging as a small cost because the unit amount is small.
Scale changes the conversation.
Sales commissions can change the value of growth
Suppose a salesperson earns:
5% commission
A KES 100,000 sale creates:
KES 5,000 commission expense
That can be completely reasonable.
The commission helped generate revenue.
But it is still part of the economics of the sale.
If discounts, delivery support and payment fees also apply, the sale can carry several variable costs at once.
The business should know what remains after all of them.
Variable costs and break-even
Variable cost directly affects break-even because it changes contribution margin.
For a simple single-product business:
Break-Even Units = Fixed Costs ÷ Contribution Margin per Unit
Suppose:
- Selling price: KES 2,000
- Variable cost: KES 1,200
- Contribution: KES 800
- Fixed costs: KES 240,000
Break-even:
300 units
Now variable cost rises to:
KES 1,400
Contribution falls to:
KES 600
New break-even:
400 units
The business now needs 100 more sales to cover the same fixed costs.
Variable cost did not just reduce profit per sale.
It pushed profit further away.
Variable costs and gross margin
For product businesses, cost of goods sold is often a major variable cost.
But not every variable cost is necessarily included in COGS.
For example, depending on the business and accounting policy:
- payment fees
- commissions
- delivery subsidies
- marketplace fees
may sit outside COGS.
That means gross margin can look healthy while wider variable selling costs make the order much weaker.
Suppose:
- Selling price: KES 2,000
- COGS: KES 1,000
- Gross profit: KES 1,000
- Gross margin: 50%
Now add:
- payment fee: KES 40
- delivery subsidy: KES 300
- sales commission: KES 100
Additional variable costs:
KES 440
Contribution after those variable costs:
KES 560
The gross margin did not lie.
It simply did not answer the whole question.
A sale can have a strong gross margin and a weak contribution margin.
Variable cost is not the same as COGS
These terms overlap, but they are not identical.
Variable cost describes how a cost behaves as activity changes.
COGS is an accounting category describing costs associated with goods sold.
Some COGS may be variable.
Some variable costs may sit outside COGS.
The distinction matters because they answer different questions.
Variable cost is not the same as OPEX
OPEX describes operating expenses.
Variable cost describes cost behaviour.
An operating expense can be variable.
For example:
- sales commission
- usage-based software
- some delivery costs
- certain transaction fees
may be operating expenses that vary with activity.
But OPEX can also contain fixed costs such as rent or salaried admin payroll.
Different label.
Different question.
Variable cost is not just a changing bill
A cost changing from one month to another does not automatically make it variable.
Suppose electricity was:
KES 20,000
last month and:
KES 30,000
this month.
That change alone does not prove the entire cost is variable.
Part may be fixed.
Part may depend on usage.
Or the rate may have changed.
To classify the cost properly, ask what caused the movement.
Some variable costs are step-like in real life
A cost can behave variably without moving perfectly with every unit.
Suppose one rider can handle:
30 deliveries per day
At 20 deliveries, the business uses one rider.
At 30, still one.
At 31, it may need another rider.
The cost does not increase smoothly with every order.
It jumps when capacity is exceeded.
Real businesses often have these mixed behaviours.
That is why management analysis should not force perfect textbook patterns onto messy operations.
Variable cost per unit can fall with scale
Variable cost per unit is not always constant.
Suppose a supplier charges:
- KES 1,000 per unit at 100 units
- KES 900 per unit at 500 units
- KES 850 per unit at 1,000 units
The business gains a volume discount.
Variable cost per unit falls.
That improves contribution margin, assuming selling price stays the same.
Scale can improve unit economics.
But not every business gets cheaper as it grows.
Variable cost per unit can rise with scale
Growth can also make variable cost more expensive.
This can happen when:
- normal suppliers run out of stock
- express freight is needed
- overtime becomes necessary
- delivery zones expand
- returns increase
- quality falls
- expensive channels are used
- discounts become heavier
The business sells more.
The variable cost per sale gets worse.
That is growth worth questioning.
Scale is only attractive when the economics survive the scale.
Variable costs by product
Different products can carry very different variable-cost structures.
| Product | Selling price | Variable cost | Contribution |
| Product A | KES 2,000 | KES 1,000 | KES 1,000 |
| Product B | KES 2,000 | KES 1,500 | KES 500 |
| Product C | KES 2,000 | KES 1,700 | KES 300 |
All three products generate the same revenue per sale.
But the amount available to cover fixed costs and profit is very different.
Revenue alone cannot rank them properly.
Variable costs by channel
The same product can have different variable costs depending on where it sells.
A direct WhatsApp order may carry:
- product cost
- packaging
- payment fee
- rider subsidy
A marketplace order may carry:
- product cost
- packaging
- marketplace commission
- payment or settlement fees
- promotional charges
A wholesale order may carry:
- lower selling price
- larger quantities
- different packaging
- different delivery economics
The product is the same.
The sale is not.
Variable costs in retail
Common retail variable costs can include:
- inventory cost
- packaging
- payment-processing fees
- sales commissions
- delivery support
- marketplace fees
- certain promotional costs tied directly to sales
Suppose:
- Revenue: KES 2,000,000
- Variable costs: KES 1,300,000
- Contribution: KES 700,000
- Fixed costs: KES 500,000
Operating contribution after fixed costs:
KES 200,000
If variable cost rises by only 10%:
New variable cost:
KES 1,430,000
Contribution:
KES 570,000
Amount after fixed costs:
KES 70,000
A 10% increase in variable cost reduced the amount after fixed costs by 65%.
That is why small cost movements can matter so much when the remaining room is thin.
Variable costs in wholesale
Wholesale often depends on volume.
Suppose:
- Selling price per case: KES 10,000
- Variable cost per case: KES 8,500
- Contribution: KES 1,500
At 100 cases:
Contribution:
KES 150,000
At 1,000 cases:
Contribution:
KES 1,500,000
The model can work well if volume is reliable and fixed costs are controlled.
But a supplier increase of KES 500 per case cuts contribution to:
KES 1,000
At 1,000 cases, that cost increase removes:
KES 500,000
of contribution.
Thin contribution makes small cost changes expensive at scale.
Variable costs in a service business
Service businesses also have variable costs.
Examples can include:
- contractor payments per job
- materials used per customer
- commissions
- transaction fees
- transport per visit
- consumables
- direct labour that varies with jobs
Suppose:
- Average job price: KES 20,000
- Variable cost per job: KES 8,000
- Contribution: KES 12,000
At 20 jobs:
Contribution:
KES 240,000
At 40 jobs:
Contribution:
KES 480,000
The business still needs to cover fixed costs after that.
Variable costs in SaaS
Software businesses can have variable costs too.
Examples may include:
- usage-based cloud infrastructure
- payment-processing fees
- third-party API costs
- customer-support costs that scale with usage
- messaging costs
- per-user service costs
A SaaS business can have high gross margins and still care deeply about variable cost.
If serving each additional customer becomes too expensive, scale can weaken rather than improve unit economics.
What is a good variable cost percentage?
There is no universal good percentage.
A 70% variable-cost ratio may be normal in one business and disastrous in another.
The useful questions are:
- How much contribution does each sale leave?
- Is contribution enough to cover fixed costs?
- Is variable cost per unit improving or worsening?
- Which products carry the strongest contribution?
- Which channels add expensive variable costs?
- Are discounts making variable cost heavier relative to revenue?
- Are supplier increases being passed through?
- Is growth improving or weakening unit economics?
The goal is not simply the lowest variable cost.
The goal is a cost structure that leaves enough contribution for the business to work.
Common variable-cost mistakes
1. Looking only at revenue growth
More sales can mean more variable cost.
2. Ignoring per-order costs
Packaging, payment fees and delivery support can become material at scale.
3. Treating COGS and variable costs as identical
They can overlap, but they are not the same classification.
4. Using old supplier costs
Contribution becomes wrong when variable cost data is stale.
5. Ignoring discounts
The cost may stay the same while the selling price falls.
6. Assuming variable cost per unit never changes
Volume can make some costs cheaper and others more expensive.
7. Comparing products by revenue alone
Two KES 2,000 sales can leave very different contribution.
8. Ignoring channel costs
The same product can carry different economics across channels.
9. Treating every changing expense as variable
The cause of the movement matters.
10. Celebrating scale before checking unit economics
More volume is not enough if each extra sale leaves too little behind.
How to manage variable costs better
Know the cost per sale
Do not stop at supplier cost.
Understand the wider costs that move with each order.
Keep supplier costs current
Old cost creates false contribution.
Track discounts beside cost
A lower price can make the same variable cost much heavier.
Review delivery and payment costs
Small per-order amounts can become large totals.
Compare products by contribution
Revenue alone is not enough.
Compare channels separately
Marketplace, retail, wholesale and direct sales can have different variable-cost structures.
Watch cost per unit as volume grows
Scale should improve the economics, not quietly weaken them.
Recalculate break-even when variable costs move
Higher variable cost raises the sales volume needed to cover fixed costs.
How Belvara helps you keep variable costs visible
Variable costs are easy to miss because they are spread across the sale.
The supplier invoice is in one place.
Delivery is somewhere else.
Payment fees are deducted automatically.
Discounts sit inside sales records.
Packaging is bought separately.
Marketplace commissions appear later.
Belvara helps keep relevant business records closer together so the owner can understand what each sale actually leaves behind.
See when cost per sale is changing
If supplier costs rise, delivery becomes more expensive or payment fees increase, contribution can shrink even when selling prices stay the same.
Keeping those records closer to sales makes the change easier to investigate.
Read discounts beside variable cost
A promotion can increase orders while leaving much less contribution per sale.
Belvara helps keep the records needed to compare realised selling price with the costs attached to the order.
Compare products and channels
Different products and channels can create the same revenue but very different contribution.
Keeping sales and related cost records together gives the owner a stronger basis for comparison.
See growth in context
More orders can look exciting.
Belvara helps keep the cost side close enough to ask the harder question:
Did the extra volume create enough extra contribution?
Belvara view: Variable costs should not disappear inside revenue growth. The business needs to know what each extra sale costs and what it still leaves behind.
Do not confuse more activity with better economics
Busy businesses are easy to admire.
More orders.
More parcels.
More customers.
More payments.
More staff moving.
But activity is not the same as strength.
If each additional order brings:
- higher product cost
- more delivery support
- more payment fees
- heavier discounts
- more returns
- more fulfilment cost
the business can scale activity faster than contribution.
That is not automatically healthy growth.
More sales are only better when the economics of the extra sale are still worth having.
The takeaway
Variable costs are costs that change with the level of sales, production or business activity.
Examples can include:
- product cost
- packaging
- commissions
- transaction fees
- delivery costs
- direct materials
- usage-based costs
The basic relationship is:
Contribution Margin = Revenue − Variable Costs
And for one unit:
Contribution Margin per Unit = Selling Price − Variable Cost per Unit
That matters because every extra sale can create both:
- more revenue
- more cost
The business needs to know what survives after both happen.
So the better question is not:
“Did we sell more?”
It is:
“What did each extra sale cost us, and how much did it still leave behind?”
That is where variable cost becomes a management tool instead of another expense category.
Frequently Asked Questions About Variable Costs
What are variable costs in simple terms?
Variable costs are costs that change as the level of sales, production or activity changes.
What are examples of variable costs?
Examples can include product cost, packaging, commissions, transaction fees, delivery costs, direct materials and other costs linked to each sale or unit of activity.
What is variable cost per unit?
Variable cost per unit is the amount of variable cost attached to one unit sold or produced.
How do I calculate total variable cost?
Use:
Variable Cost per Unit × Number of Units
What is the difference between fixed and variable costs?
Fixed costs do not usually change directly with each extra sale in the short term. Variable costs do.
Is COGS a variable cost?
COGS often contains variable costs, but the two terms are not identical. Variable cost describes behaviour. COGS is an accounting category.
Is packaging a variable cost?
Packaging used per order is commonly a variable cost because total packaging cost rises as order volume rises.
Are transaction fees variable costs?
Transaction fees charged per sale or as a percentage of revenue are commonly variable costs.
Is delivery a variable cost?
Delivery linked directly to each order can behave as a variable cost. Exact accounting classification may depend on the business and treatment used.
Are commissions variable costs?
Commissions tied directly to sales are commonly variable costs.
Is salary a variable cost?
A fixed salary is usually not variable in the short term. Piece-rate, job-based or commission-based labour can behave differently.
Is electricity a variable cost?
Electricity can be fixed, variable or mixed depending on how the charge behaves.
Can variable cost per unit change?
Yes. Supplier pricing, volume discounts, overtime, express freight and other factors can change variable cost per unit.
How do variable costs affect break-even?
Higher variable costs reduce contribution per sale, which increases the number of sales needed to cover fixed costs.
How do discounts affect variable cost?
Discounts do not necessarily reduce variable cost. They lower selling price, which can make the same variable cost consume a larger share of revenue.
Can sales grow while contribution gets weaker?
Yes. If variable cost per sale rises or discounts increase, revenue can grow while contribution improves only slightly or even worsens.
What is a good variable cost percentage?
There is no universal good percentage. It depends on business model, contribution margin, fixed costs, industry and pricing.
How does Belvara help with variable costs?
Belvara helps keep relevant records behind each sale closer together, including sales, product costs, discounts, delivery, payment costs and other operating records. That gives the owner better context when the cost of each sale changes.
What should I learn after variable costs?
Useful next concepts include contribution margin, fixed costs, break-even point, gross margin, operating leverage and unit economics.