Discount Calculator

What Is a Discount Calculator?

A discount calculator takes an original price and a discount and returns the sale price and the amount saved. This one handles both percent off and dollar off, supports stacked discounts (more than one applied in sequence), and adds a readout no other discount calculator gives you: what the discount does to your profit margin, not just the price.

Sale price = Original price − (Original price × Discount % / 100)

A $100 item at 20% off sells for $80, a $20 saving. That part is simple. The part that decides whether the promotion was a good idea is what those $20 came out of, and the answer is your margin.

How to Calculate a Discount

1. Start with the original price.
2. For a percentage discount, multiply the price by the discount rate and subtract it. For a dollar discount, subtract the dollar amount directly.
3. The result is the sale price; the difference from the original is the amount saved.

Amount saved = Original price − Sale price

A $64 item at 25% off saves $16 and sells for $48. A $64 item with $10 off sells for $54. Enter either style above, or mix them in a stack.

Stacked and Multiple Discounts

Stacked discounts apply one after another, each on the already-reduced price, which is why they never add up the way people expect. A 20% discount followed by a 10% discount is not 30% off:

• Start: $100
• After 20% off: $80
• After a further 10% off: $72

That is 28% off, not 30%. The second discount is taken on $80, not on the original $100. The calculator above lets you add as many discount stages as you like, in order, and shows the true effective discount at the end. This matters for "extra 10% off sale prices" promotions, loyalty codes layered on a markdown, and any BOGO-style offer expressed as sequential cuts.

What a Discount Actually Does to Your Margin

Here is the gap every other discount calculator leaves open. A discount does not come out of revenue evenly, it comes entirely out of your contribution margin, because your cost per unit does not change when you cut the price. Every dollar of discount is a dollar off your profit.

The math is unforgiving. Take a $100 product at a 50% gross margin, so it costs you $50 and earns $50 of contribution.

	Before discount	After 20% off
Price	$100	$80
Unit cost	$50	$50
Contribution	$50	$30

A 20% price cut removed 40% of the contribution. The rule of thumb: at a 50% margin, a discount erodes contribution at roughly twice the discount rate. At thinner margins it is worse. A 20% discount on a 30% margin product cuts contribution by about 67%, and a 20% discount on a 25% margin product cuts it by 80%. Push the discount past your margin and you sell below cost, you lose money on every order the promotion brings in. Enter your gross margin in the calculator and it shows the contribution before and after, the percentage eroded, and whether you have crossed into loss.

The Volume a Discount Has to Earn Back

Because a discount shrinks the profit on every order, it has to bring in enough extra volume to make up the difference. At the $100 / 50% margin example, the discounted order earns $30 instead of $50. To recover the $20 given up on a single order, you need about 0.7 of an extra sale at the discounted contribution, and that is just to break even on that one order, before counting the customers who would have bought at full price anyway and just took the discount for free.

This is why blanket discounts so often lose money quietly: they cut margin on the buyers you already had, and only pay off if they genuinely convert new demand at scale. A discount targeted at slow-moving inventory or genuinely price-sensitive segments is a different calculation from a sitewide code every existing customer uses.

Worked Example

A brand runs a 25% off code on a $60 product with a 45% gross margin.

Input	Value
Original price	$60.00
Discount	25%
Sale price	$45.00
Amount saved	$15.00
Unit cost	$33.00
Contribution before	$27.00
Contribution after	$12.00
Contribution eroded	56%

A 25% discount cut the contribution on this product by more than half. The store still makes $12 per order, so it is not selling below cost, but it now needs more than double the unit volume to earn the same total profit it made before the sale. Seeing that before launching the promo is the difference between a discount that grows profit and one that just moves revenue around.

The Bottom Line on Discounts

A discount calculator finds the sale price and savings; the useful version also shows what the cut does to profit, since a discount comes straight out of margin. Percentages stack on the reduced price, not the original, so they never simply add. To see how every live promo code and markdown affected contribution margin and net profit across your whole store, not just top-line sales, see how Daymark connects Shopify and your cost data in plain English. It also pairs with the contribution margin calculator and the margin calculator.