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Discount Calculator

Work out the price after a discount, the discount percentage between two prices, the original price before a sale, and the true total when discounts stack.

✓ Last reviewed: Sources: Successive Discounts — math-only-math.com

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The starting price, before the discount.

If the type is percent, enter the percentage (e.g. 20). If it's a fixed amount, enter the amount.

Advanced options

Discounts apply one after another to the already-reduced price — they don't add up (e.g. −20% and −10% is −28%, not −30%). Order matters when you mix a percentage with a fixed amount.

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What the discount calculator does

The discount calculator answers the four questions behind every sale: what will I pay after the discount, how much do I save, what percentage off is it really, and what was the price before the markdown. You enter what you know — a price and a discount, or two prices — and it works out the rest instantly. It’s for anyone chasing deals, comparing offers, or checking whether stacking one discount on another is actually worth it.

The discount calculator works in three modes, which you pick at the top:

  • Price after discount — you know the starting price and the discount (as a percent or a fixed amount) and want the final price and the saving.
  • Original price — you can see the reduced price and know the discount, and the calculator reconstructs the pre-sale price (the reverse mode).
  • Discount % from two prices — you have both prices (before and after) and want to know what percentage off that is.

Every mode returns the same four numbers: the original price, the price after discount, how much you save, and the effective discount percentage. On top of that you get a step chart showing how the price falls after each discount, and a “what you pay vs save” ring that shows at a glance how much of the price the deal knocks off. You can also compare your discount against what other people have calculated.

In the advanced options you switch on stacking discounts — several reductions applied one after another (a sale plus a coupon code, say). This is where shoppers make their most common mistake: discounts multiply, they don’t add up. The calculator is currency-agnostic — it works in plain numbers, so it fits any market.

How to use the calculator

  1. Choose the mode. “Price after discount” is the default — the most common case. Switch modes if you instead want to reconstruct the original price or work out a percentage from two prices.
  2. Enter the prices and discount. In the basic mode you give the starting price and the discount — you choose whether it’s a percent (e.g. 25) or a fixed amount (e.g. 50). In “discount % from two prices” you simply enter both prices.
  3. Read the result. The price after discount, the saving, the effective discount and the original price appear immediately, along with the charts.

If you’re combining several deals, open the advanced options:

  • Stacking discounts — turn this on to add a second, third and fourth discount. Each one applies to the price already reduced by the previous one, in the order you enter them.
  • Order matters when you mix a percent with a fixed amount (e.g. −20% and −10) — that’s why the discount slots are laid out in sequence. With percentages only, the order doesn’t change the result.

How a discount is calculated: formulas and examples

It all comes down to a few simple operations. Here’s each mode with a worked example.

Percentage discount — price after discount:

final price = price × (1 − percent ÷ 100)

A price of 200 with a 25% discount: 200 × (1 − 0.25) = 200 × 0.75 = 150. You save 50, and the effective discount is, of course, 25%. The saving is always the difference: original price minus final price.

Fixed-amount discount — price after discount:

final price = price − discount amount

A price of 250 with a 50 discount (in currency, not percent): 250 − 50 = 200. You save 50. To see what percentage that is, divide the saving by the starting price: 50 ÷ 250 = 0.20, an effective discount of 20%. Handy when you want to compare a fixed-amount deal with a percentage one.

Original price (reverse discount):

original price = final price ÷ (1 − percent ÷ 100)

You see a price of 150 tagged “−25%” and want to know what it cost before. Divide: 150 ÷ 0.75 = 200. This is the exact inverse of the first example — which is why both give the same 200-and-150 pair. With a fixed-amount discount it’s even simpler: original price = final price + discount amount.

Discount % from two prices:

discount % = (original − final) ÷ original × 100

The price dropped from 200 to 150: (200 − 150) ÷ 200 × 100 = 50 ÷ 200 × 100 = 25%. One caveat for this mode: if the “new” price is higher than the old one, that’s not a discount but a price rise — the calculator then shows a negative value and flags it clearly.

Stacking discounts: why they multiply instead of adding up

This is the single most important idea here, and the classic trap in any sale. When two percentage discounts land one after the other, you don’t add them — you multiply what’s left of the price:

total discount = 1 − (1 − p₁ ÷ 100) × (1 − p₂ ÷ 100)

Take a price of 100, a 20% discount, then a second 10% discount. It’s tempting to say “30% off in total.” But the second 10% applies to the already-reduced price, not the full one:

  1. After the first discount: 100 × 0.80 = 80.
  2. After the second discount: 80 × 0.90 = 72.
  3. You save 28, so the effective discount is 28% — not 30%.

The same logic holds for three or more reductions. A price of 100 with discounts of 30%, 20% and 10% in turn: 100 × 0.70 × 0.80 × 0.90 = 50.40. The naive sum would suggest 60%, but the real discount is 49.6%. The more discounts you stack, the wider the gap between the eyeballed figure and reality — and the more it pays to actually run the numbers.

Order matters when you mix a percent with a fixed amount. With percentages only it’s commutative (20% then 10% gives 28% either way). But a percent and a fixed amount are a different pair. A price of 200:

  • First −20%, then −10 (amount): 200 × 0.80 = 160, then 160 − 10 = 150. You save 50.
  • First −10 (amount), then −20%: 200 − 10 = 190, then 190 × 0.80 = 152. You save 48.

The same two discounts, but the result differs by 2 — because a percent applied to a larger amount knocks off more. That’s why the calculator keeps the order in which you enter the discounts, and shows you what the reversed order would have produced.

Frequently asked questions

How do I calculate the price after a discount?

Multiply the starting price by (1 − percent ÷ 100). For a 25% discount you multiply by 0.75, for 30% by 0.70, and so on. Example: 200 × 0.75 = 150, so a 25% discount leaves you paying 150 and saving 50. If the discount is a fixed amount, just subtract that amount from the price. The calculator above does this instantly and also shows the effective discount percentage.

How do I find the discount percentage between two prices?

Subtract the reduced price from the original price, divide by the original price, and multiply by 100: discount % = (original − final) ÷ original × 100. Example: the price dropped from 200 to 150, so (200 − 150) ÷ 200 × 100 = 25%. If the new price is higher than the old one, it’s a price rise rather than a discount, and the calculator marks it with a negative value.

How much will I save with a 20% discount?

The saving on a percentage discount is the price times the percent divided by 100. For 20% you multiply the price by 0.20: on a price of 200 you’d save 40 and pay 160. For a different percentage you just change the multiplier — 25% is times 0.25, 30% is times 0.30. Enter your own price and discount and the calculator shows the exact saving and the amount to pay.

How do you calculate two discounts stacked together (e.g. a sale plus a coupon)?

Apply the discounts in sequence — take the second off the price already reduced by the first, not off the full price. A price of 100 with 20% off, then 10% off: 100 × 0.80 = 80, then 80 × 0.90 = 72. The combined discount is 28%, not 30%. In the calculator, switch on “stacking discounts” in the advanced options and enter the reductions in the order they actually apply.

Do discount percentages add up — is 20% + 20% the same as 40% off?

No, percentage discounts multiply rather than add: total discount = 1 − (1 − p₁ ÷ 100) × (1 − p₂ ÷ 100). Two 20% discounts give 1 − 0.80 × 0.80 = 0.36, which is 36% off, not 40% — because the second 20% is taken off the already-reduced price. Likewise 20% then 10% is 28%, not 30%. The more discounts you stack, the wider the gap between the simple sum and the real discount.

How do I find the original price before a discount (reverse discount)?

Divide the reduced price by (1 − percent ÷ 100). You see a price of 150 tagged “−25%”: 150 ÷ 0.75 = 200, so it originally cost 200. This is the exact inverse of working out the price after a discount. If you know the discount as a fixed amount instead of a percent, just add that amount to the reduced price. In the calculator, choose the “original price” mode.

How do I calculate a discount when the price includes tax (or excludes it)?

The calculator works out the pure relationship between prices and doesn’t add or remove any tax. A percentage discount behaves the same whether you enter a tax-inclusive or tax-exclusive price — 20% off a $120 gross price and 20% off a $100 net price are both the same one-fifth reduction. What matters is that the starting and final prices use the same basis (both inclusive or both exclusive). The tax and discount amounts themselves are outside this calculator’s scope.

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