Gross margin is the deck number. Contribution margin is the decision number.
A founder approved 25% off believing he held 75% margin. He held 47.5%, and after the discount, 30%. Gross margin answers whether this is a good business. Contribution margin answers whether to do this deal at this price, and it is the one almost nobody computes.
Summary
- Gross margin is revenue minus your direct cost of delivery: the deck number, and the right number for a valuation conversation.
- Contribution margin subtracts every cost that varies with serving that customer, including support, customer success, amortised implementation, gateway fees and the financing cost of a ninety-day receivable. It is the number that governs discounting.
- On the same ₹6,00,000 contract the two numbers are 74.5% and 47.5%, twenty-seven points apart, and founders discount against the higher one.
A founder I was speaking with recently approved a 25% discount to win a competitive deal. His reasoning was sound on its face. "We're at about 75% gross margin. Even after a quarter off, we're still making good money on it." He was not. After that discount the deal was running at roughly 30% , and his customer acquisition cost on it would take more than two and a half years to come back. He had given away well over a third of the economics of that customer, and every number he was looking at told him he hadn't. Nobody lied to him.
He was simply reading the wrong margin.
There are three margin numbers, and they answer different questions
Most founders use one of them for everything. That is where the trouble starts.
Gross margin is revenue minus your direct cost of delivery. For a software company: hosting, third-party APIs, inference, data storage. This is the number in your investor deck, and it is the right number for a valuation conversation.
Contribution margin is revenue minus every cost that varies with serving that specific customer. Direct delivery, yes, but also support, customer success time, amortised implementation, payment gateway charges, and the financing cost of a ninety-day receivable. This is the number that governs discounting, and almost nobody computes it.
Net margin is what is left after everything, including your fixed costs. Useful for the board. Useless in a negotiation.
Gross margin answers is this a good business? Contribution margin answers should I do this deal at this price? Those are different questions and they have different answers.
The arithmetic, with real numbers
Take a B2B software company with a ₹6,00,000 annual contract.
Direct costs: what varies per unit delivered
| Item | ₹ per year |
|---|---|
| Cloud compute and storage attributable to usage | 42,000 |
| Third-party API pass-through (KYC, enrichment, SMS) | 31,000 |
| LLM inference at observed usage | 68,000 |
| Payment gateway and collections (~2%) | 12,000 |
| Subtotal | 1,53,000 |
Gross margin: 74.5%. The deck number. It looks healthy, and it is. But serving this customer costs more than delivering to them:
Cost to serve: what varies per customer, whatever the volume
| Item | ₹ per year |
|---|---|
| Support: 4.5 tickets a month at ₹550 loaded cost | 30,000 |
| Customer success: 0.04 csm fte at ₹18L loaded | 72,000 |
| Amortised implementation (₹1.8L over a 3-year life) | 60,000 |
| Subtotal | 1,62,000 |
Total cost of serving this customer: ₹3,15,000.
Contribution margin: 47.5%.
Two numbers, same customer, both correct, twenty-seven points apart. And the founder above was making his discount decision on the first one.
The costs founders routinely leave out
In our work across a large number of Indian startups and MSMEs, the same items go missing from the floor calculation again and again.
Implementation and onboarding. It sits in operating expense, so it disappears from margin thinking entirely. It is a real cost of serving that customer. And in Indian B2B it is very often waived to close the deal, which means you have granted a 100% discount on a real cost, without approval, invisible in every report you read.
Customer success. You call it retention. It behaves as cost-to-serve. Allocate it.
Support. Varies enormously by segment, and usually in the wrong direction. Ticket volume per customer is frequently five to ten times higher in the SMB tier you priced lowest.
AI inference. The structural margin story of this decade. Classic software businesses run 75% to 85% gross margins. AI-native products frequently land at 40% to 65%, because inference is genuinely variable and genuinely large. If your costs scale with usage but your price does not, you have built a business that becomes less profitable as it succeeds.
The financing cost of your receivable. If your enterprise customer pays in ninety days and your cost of capital is 14%, that receivable costs you roughly 3.5% of the invoice. It is a permanent, silent discount on every contract, granted by a sales team that has been told to hold the price and sincerely believes it did.
For a D2C business, add cash-on-delivery handling, return-to-origin cost, reverse logistics, marketplace commission and coupon discounts. In a category running 25% RTO, a product showing a healthy 45% gross margin can be contribution-negative on the COD channel while comfortably profitable on prepaid orders from your own website. A blended margin report hides this completely.
Now the number that should change your behaviour
Here is the single most useful piece of arithmetic in pricing. When you cut price by d and your contribution margin is CM, the extra volume you need simply to break even is:
Required volume increase = d ÷ (CM − d)
The extra volume a discount demands, just to stand still
| Discount given | Extra volume at 50% contribution margin | Extra volume at 30% contribution margin |
|---|---|---|
| 5% | 11% | 20% |
| 10% | 25% | 50% |
| 15% | 43% | 100% |
| 20% | 67% | 200% |
| 25% | 100% | 500% |
| 30% | 150% | Infinite: you are at zero contribution |
Read the 30% column again. At 30% contribution margin, a 20% discount requires you to triple your volume to be no worse off. No sales team in India is winning three times the business because the price came down a fifth.
And notice where this bites hardest: the thinner your contribution margin, the less you can afford to discount, and thin margins are almost always exactly where the discounting culture is worst. The full grid, at 50%, 30% and 20% contribution margin, is set out in the discount breakeven table.
The same arithmetic, running the other way
Affordable volume loss = p ÷ (CM + p)
At 50% contribution margin, a 10% price increase leaves you better off even if you lose 16.7% of your customers.
Most companies would not lose 3%.
That asymmetry, discounts demanding enormous volume while increases tolerate large losses, is the entire reason pricing outperforms every other lever available to you. A rupee of recovered price carries no incremental cost. It goes almost entirely to profit.
The rule
You may discount into your contribution margin. You may never discount through it.
That is the floor. It is one number, per product, per segment, and it should be written down and carried by every person in your company who quotes a price. Protecting that number is what a VP of Pricing exists to do in a large corporate. In your company, it has to live on a card.
Build yours this week
None of this needs software or a consultant.
- One. Take your last twelve months of contracts and list every cost that varies with serving a customer. Not what your accountant files as COGS: what actually moves when you add one more customer. Include implementation, support, success, gateway fees, and the financing cost of your payment terms.
- Two. Compute contribution margin per segment. Expect the SMB number to be far worse than you assume.
- Three. Build your discount table on your real numbers, not the illustrative ones above. Print it. Give it to every salesperson.
- Four. Write the floor down, and build a four-row discount authority matrix around it: who may approve what depth, and what justification is required. The friction is the point.
- Five. Rank every customer by contribution margin. Some of your largest accounts by revenue will be at the bottom. That is not a reporting error, that is the finding.
You already know your to the week. Now go and find out what you must not go below.
Frequently asked questions
What is the difference between gross margin and contribution margin?
Gross margin subtracts only your direct cost of delivery. Contribution margin subtracts every cost that varies with serving that customer: delivery, plus support, customer success, amortised implementation, payment processing and the financing cost of your receivables. Gross margin tells you whether the business is good. Contribution margin tells you whether a specific deal at a specific price is good.
How do I calculate my contribution margin floor?
Take the price, subtract every cost that varies with serving that customer, and express what remains as a percentage. That percentage is your floor: the point below which the deal destroys value. Compute it separately for each product and each customer segment, because they differ more than you expect.
Why does discounting hurt so much more at low margins?
Because the volume required to recover a discount is discount ÷ (contribution margin − discount). As contribution margin falls toward the size of the discount, that denominator shrinks and the required volume increase explodes. At 30% contribution margin, a 30% discount requires infinite volume: you are earning nothing on every unit.
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