01
Enter price and cost
Your normal full price and your all-in unit cost. Together they set the margin the discount will eat into.
Discount Profit Calculator
Before you run a discount, see the exact volume it needs and your safe floor.
Updated Reviewed by Sajid Hussain· Editor
Is your sale actually making money?
The discount profit calculator that shows the volume a promo really needs
A discount's profit impact is the change in total margin caused by reducing a product's price — measured by how much the contribution margin falls, not by how much the price falls. Lowering a price by 20% does not cut profit by 20%: unit cost stays fixed, so the full price drop compresses the smaller margin by a larger fraction. On a typical 40% margin product, a 20% discount can erase roughly half the profit per unit, meaning the break-even sales volume is nearly 2× — twice as many orders just to stand still. This calculator shows the exact sales lift a planned discount requires to break even on profit, the max safe discount before every sale loses money, and contribution margin before and after — in any currency, with or without a channel fee.
The trap in numbers. Sell a product priced at 30 that costs 12, with a 15% channel fee. Your profit per unit is 30 − 12 − 4.50 = 13.50. Take 20% off and the price falls to 24; the fee drops to 3.60, so profit is now 24 − 12 − 3.60 = 8.40. The price fell 20%, but profit per unit fell about 38% — from 13.50 to 8.40. To make the same total profit you must sell 13.50 ÷ 8.40 ≈ 1.6× as many units: 60% more volume, not 20%.
What most discount calculators hide. They show the new price and stop. This tool computes the fee-aware contribution margin before and after the cut, the exact extra volume to break even on profit, and — crucially — the maximum safe discount: the deepest markdown you can run before every single sale starts losing money.
The mirror image of the Selling Price Calculator. That tool works forward from a target margin to the price you should charge. This one works backward from a price cut to the sales lift it requires and the floor you must not cross. Use it before you schedule a coupon, a flash sale, a Prime Day deal, or a clearance markdown.
Sales tax excluded — correctly. You collect tax from the buyer and remit it to the government — it's never your money and never a cost, so folding it into margin math would distort every number. Because the tool uses per-unit margins and ratios, it works in any currency.
Quick facts
- Headline answer
- Extra units needed to break even on the promo
- The floor
- Max safe discount before every sale loses money
- Fee-aware
- Contribution margin after channel + payment fees
- Before vs after
- Profit per unit and margin %, both ways
- Works anywhere
- Currency-agnostic — any marketplace, any country
- The trap exposed
- Why 20% off can need 60%+ more volume
How it works
From a planned discount to the real volume it needs
Four short steps to know whether your promotion will actually pay off.
02
Set the discount
The % off you plan to run, plus your channel/payment fee so the margin math is accurate.
03
Add volume (optional)
Drop in your current sales to convert the percentage lift into a hard number of extra units.
04
Read the verdict
See the extra volume to break even, the profit you keep per unit, and the deepest discount you can safely run.
Steps to use the Discount & Promotion Profit Calculator: Enter price and cost, Set the discount, Add volume (optional), Read the verdict.
Formula
Exactly what the calculator computes
No black boxes — the margin and break-even math, in plain algebra. Everything is per unit, after the channel fee.
01
Contribution margin before the discount
CM Before = Price − Unit Cost − (Price × Fee Rate)
Your profit on one unit at full price, after the variable channel/payment fee. This is the baseline the discount cuts into. (Fixed costs aren't included — a promo doesn't change your rent, so contribution margin is the right lens.)
02
Contribution margin after the discount
New Price = Price × (1 − Discount%); CM After = New Price − Unit Cost − (New Price × Fee Rate)
The discount lowers the price (and the fee with it), but your unit cost stays fixed — so the whole price cut comes out of your margin. That's why CM After falls by a much bigger percentage than the price does.
03
Extra volume to break even on profit (the headline)
Required Multiple = CM Before ÷ CM After; Extra Volume% = (Required Multiple − 1) × 100
To make the same TOTAL contribution after discounting, units must scale by the ratio of the old margin to the new one. If the new margin is half the old one, you need 2× the volume — a 100% lift — just to stand still. When CM After is zero or negative, no amount of volume can recover the profit, so the calculator flags it instead of returning infinity.
04
Break-even unit price (the floor)
Break-Even Price = Unit Cost ÷ (1 − Fee Rate)
The lowest price at which a discounted sale still nets zero. It's your cost grossed up for the fee, because the fee is charged on the (discounted) price you sell at. Sell below this and every unit loses money.
05
Maximum safe discount
Max Safe Discount% = (1 − Break-Even Price ÷ Price) × 100
The deepest % off you can run while the discounted price stays at or above break-even. Cross it and the promo becomes a guaranteed loss on every sale, no matter how many you move.
Worked example
A 20%-off sale on a product priced at 30
Watch why the volume the promo needs is triple the discount itself.
Scenario
You sell for $30.00 (it costs you $12.00) on a channel that takes 15% channel fee. You're planning a 20% off sale. How much more do you need to sell to come out even?
1
Step 1 · Profit per unit at full price
Fee on $30.00 is $4.50, so your contribution margin is $30.00 − $12.00 − $4.50 = $13.50 per unit.
CM before: $13.50/unit
2
Step 2 · Profit per unit after 20% off
The price drops to $24.00; the fee falls to $3.60. Margin = $24.00 − $12.00 − $3.60 = $8.40 — the price fell 20% but the margin fell 38%.
CM after: $8.40/unit
3
Step 3 · Extra volume to break even
You need $13.50 ÷ $8.40 = 1.6× the volume to net the same total profit — that's 60% MORE units, not 20%.
Need 60% more units (1.6×)
4
Step 4 · How low could you safely go?
Break-even price is $12.00 ÷ (1 − 15%) = $14.12. So the deepest discount that still profits is about 52.9% off — below that, every sale loses money.
Max safe discount: 52.9%
The takeaway
A 20% off promo on this product needs 60% more sales just to break even — triple the headline discount. If you don't expect that kind of lift, a smaller markdown (or a bundle) will protect more profit.
Rules of thumb
How much extra volume a discount needs
The required sales lift to break even climbs fast as the discount deepens — and faster still on thin-margin products. Rough guide at a healthy ~40% pre-discount margin.
| Metric | Poor | Average | Good | Excellent |
|---|---|---|---|---|
Discount depth Shopify Pricing Strategy Guide 2026 | 50%+ off | 25–40% off | 10–20% off | < 10% off |
Extra volume to break even HBR The Price Is Right — Pricing Research 2022 | > 100% | 40–100% | 15–40% | < 15% |
Margin % left after discount McKinsey Pricing & Revenue Growth 2023 | < 5% | 5–15% | 15–25% | 25%+ |
Headroom to max safe discount Shopify Pricing Strategy Guide 2026 | < 5 pts | 5–15 pts | 15–30 pts | 30+ pts |
Pre-discount margin NYU Stern Sector Margins 2025 | < 15% | 15–30% | 30–50% | 50%+ |
Why this calculator
Calcrux vs other discount calculators
Most "discount calculators" just subtract a percentage and show the new price. They never tell you the volume that price cut demands — which is the only number that decides whether the promo pays.
| Feature | Calcrux | Omni Calculator | Spreadsheet |
|---|---|---|---|
| Shows the discounted price | Manual | ||
| Extra volume needed to break even on profit | Manual | ||
| Fee-aware contribution margin | Manual | ||
| Maximum safe discount (the floor) | Manual | ||
| Warns when a discount loses money per unit | |||
| Absolute extra units (from your volume) | Manual | ||
| Margin % before AND after, side by side | Rare | Manual | |
| Works in any currency | Most US-only | ||
| Free, no signup | Most |
Common mistakes
Why discounts quietly lose money
Assuming 20% off needs 20% more sales
Why it matters
The discount comes out of your margin, not your revenue. On a 40%-margin product, a 20% price cut can slash profit per unit by ~50% — so you need to roughly double volume, not lift it a fifth.
Fix
Use the "extra volume to break even" figure, which divides your old margin by your new one. That ratio is the real lift you need.
Ignoring channel fees in the promo math
Why it matters
On Amazon, eBay or Etsy the fee is a % of the (discounted) price. People discount off the full price but forget the fee still eats the rest, leaving a far thinner margin than they expect.
Fix
Enter your channel/payment fee. The calculator computes contribution margin after the fee, both before and after the discount.
Discounting past the break-even price
Why it matters
A deep coupon or stacked promo can drop the price below cost-plus-fees. Then every unit loses money, and selling MORE makes the loss bigger, not smaller.
Fix
Check the "max safe discount" output before you set the deal. Stay above it unless you have a deliberate loss-leader reason.
Treating sales tax / VAT / GST as a cost
Why it matters
Tax is collected from the buyer and passed to the government. Subtracting it as if it were your expense understates your margin and makes safe discounts look unsafe.
Fix
Leave tax out of these inputs. The tool deliberately excludes it so the margin and break-even numbers are clean.
Counting the revenue lift instead of the profit lift
Why it matters
A promo can grow revenue while shrinking total profit — more units at a much thinner margin. "Sales went up" is not the same as "we made more money".
Fix
Break even on PROFIT, not revenue. The required-volume multiple is built on contribution margin, so it answers the profit question directly.
Forgetting the promo also costs you full-price buyers
Why it matters
Some customers who would have paid full price now buy at the discount. This calculator measures the margin and volume math; it doesn't model that cannibalization, which makes the real break-even even harder.
Fix
Treat the break-even volume as a floor, not a target. If you can barely hit it on paper, the promo is unlikely to pay once cannibalization is counted.
Tips
Run promotions that actually profit
Discount thin margins less
The lower your starting margin, the more brutal a discount is. A 10% margin product can need 100%+ more volume for a 20% cut — often not worth it.
Know your floor before you set the deal
Look at the max-safe-discount output first. It tells you the hard limit; design the promo inside it with room to spare for returns and ads.
Prefer bundles over deep cuts
A "buy 2, save" bundle lifts order value and dilutes fixed per-order fees, often protecting more profit than a straight percentage off.
Cap stacked promos
Coupons, sale prices, and platform deals stack. Add them up as one combined discount here so the total doesn't quietly cross break-even.
Use volume to sanity-check the lift
Enter your current sales to see the absolute extra units needed. If that number looks unrealistic for the promo window, scale the discount back.
Re-check when fees change
A higher channel fee raises your break-even price and shrinks your safe discount. Re-run the numbers whenever a marketplace changes its rates.
Use cases
When sellers reach for this calculator
The Discount & Promotion Profit Calculator works across every stage of the workflow.
Planning a flash sale or coupon
Check whether the volume the discount needs is realistic for the promo window before you schedule it.
Submitting a Prime Day / deal
See if the required price cut still clears break-even after Amazon's fee, and how thin the margin gets.
Clearing slow inventory
Find the deepest markdown that still avoids losing money on each unit — or decide that a deliberate loss-leader is acceptable.
Setting a storewide promo
Test the discount against your thinnest-margin SKU so the sale doesn't turn a winner into a loss across the catalog.
Negotiating a wholesale discount
Translate a buyer's requested % off into the extra volume you'd need to make it worth your while.
Reviewing a promo that flopped
Compare the volume you actually got to the break-even volume to see why revenue rose but profit didn't.
Glossary
Discount and promotion terms
Every important term you'll encounter in this calculator and the broader topic.
- Contribution margin
- Price minus the variable costs of one unit (cost of goods + channel/payment fees). The profit each sale contributes before fixed costs — the right lens for a promo decision.
- Break-even volume
- The number of units you must sell at the discounted price to make the same total profit as before the discount. Above it the promo adds profit; below it, it loses.
- Required volume multiple
- Old contribution margin ÷ new contribution margin. The factor your unit sales must grow by to break even — e.g. 2.0× means you must double volume.
- Max safe discount
- The deepest discount that keeps the discounted price at or above break-even. Cross it and every sale loses money regardless of volume.
- Break-even price
- Unit cost grossed up for the channel fee — the lowest price that nets zero. Below it, you pay to make each sale.
- Markdown
- A reduction from the regular price, usually to clear inventory or drive a promotion. Measured here as a discount %.
- Loss leader
- A product sold below break-even on purpose, to attract buyers who also buy profitable items. Only sensible as a deliberate strategy, not by accident.
- Cannibalization
- When a promo's discounted sales replace sales that would have happened at full price. It raises the true break-even — this tool measures the margin math, not the cannibalization.
- Channel fee
- The marketplace + payment fee charged as a % of each sale (Amazon ~15%, eBay ~13.6%, Etsy ~9.5%, Shopify/own store ~2.9%). It comes off the discounted price, not the full one.
Help & answers
Frequently asked questions
Everything you need to know about how the Discount & Promotion Profit Calculator works.
01How does a discount profit calculator work?
Enter price, cost, discount %, and channel fee. The tool computes contribution margin before and after, divides old by new to find the volume multiple needed to break even, and shows the deepest safe discount you can run. Works in any currency.
02How much more do I need to sell to break even on a discount?
The required lift = old CM ÷ new CM − 1. Example: a product priced at 30, 12 cost, 15% fee = 13.50 profit/unit. Take 20% off → 8.40. You need 13.50 ÷ 8.40 ≈ 1.6× volume — about 60% more — to break even. The lower your margin, the bigger the lift.
03Why does a 20% discount need so much more than 20% more sales?
Because the cut comes from margin, not revenue. Drop the price 20% and unit cost stays fixed — so the full cut reduces the smaller margin. If your margin was 40%, a 20% cut can erase roughly half of it, meaning you'd need to nearly double sales. That gap is why this calculator exists.
04What is the maximum safe discount I can offer?
Break-even = unit cost ÷ (1 − fee rate); max safe discount = (1 − break-even ÷ full price) × 100. Example: a product priced at 30, 12 cost, 15% fee → break-even ≈ 14.12, max safe ≈ 53% off. Beyond that every sale loses money regardless of volume.
05What is contribution margin and why use it for discounts?
Contribution margin = profit from one sale after COGS and channel fee, before fixed costs. Fixed costs don't change with a promo, so CM is the right lens. Old CM ÷ new CM gives the volume multiple needed to break even — all the key outputs are built from this ratio.
06Should I include marketplace fees in the discount calculation?
Yes — fees are often the difference between a promo that profits and one that doesn't. On Amazon, eBay, Etsy, or Shopify the fee is a % of the sale price. Enter your fee (Amazon ~15%, eBay ~13.6%, Etsy ~9.5%, Shopify ~2.9%) and it's deducted from both margins.
07Should I include sales tax or VAT in this calculator?
No. Sales tax and VAT go to the government — never your money, never a cost. Including them distorts your margin and makes safe discounts look unsafe. Leave tax out. The tool uses per-unit ratios so it works the same in the US, EU, UK, India, or anywhere else.
08What happens if my discount is too deep?
If the discounted price is below break-even, profit per unit goes negative and the calculator warns you. No volume recovers it — more sales multiply the loss. The max safe discount shows how much to pull back, unless you're deliberately running a loss leader.
09Can I see the actual number of extra units I need, not just a percentage?
Yes. Enter your current sales in the optional "Units You Sell Now" field and the calculator converts the % lift into a hard number of extra units. If hitting that number in the promo window looks unrealistic, the discount is too deep.
10How is this different from a selling price calculator?
Mirror images. A selling price calculator works forward: target margin → price to charge. This one works backward: price cut → sales lift needed and safety floor. Use the selling price tool to set your everyday price; use this one when planning any discount on top of it.
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Category
Ecommerce Seller Operations
Subcategory
financial profitability
Availability
Global · 9 markets
Price
Free forever
Topics
discount profit calculatorpromotion break-evendiscount margin impactsales liftmarkdownprice cutcontribution marginecommercepromotion planningcalculatorhow to calculate discount profitsale break-even calculator
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