Discount calculator
Stacked discounts multiply rather than add. Twenty per cent off 100 leaves 80; a further ten per cent off that leaves 72, not 70. The effective discount is 28%, and the gap widens as the numbers get bigger; 50% then 50% is 75% off, not 100%. Retailers know this, which is why "an extra 20% off sale prices" reads better than the single number it actually amounts to.
Figures are before tax unless a tax field is shown. Currency is whatever you type, nothing is converted.
A discount is the price multiplied by one minus the percentage: 20% off 100 leaves 80. Two stacked offers multiply rather than add, so 30% then 20% leaves 112 from 200 — an effective 44% off, not 50%. The same four numbers also give the sale price to advertise for a target reduction.
How to calculate a discount
Working backwards from two prices is the more useful direction in a sale, because it exposes what a claimed discount is actually worth. A "50% off" that runs from an inflated reference price is a different offer from the same headline against a price the item genuinely sold at, and the only way to tell is to know what it cost before the sale started. In several jurisdictions the reference price must be the lowest price charged in the preceding thirty days for exactly this reason. From the till side, the arithmetic runs the other way and the question becomes what a markdown costs: a discount comes entirely out of margin rather than out of cost, so 25% off a product carrying a 40% margin removes not a quarter of the profit but well over half of it. Stacking makes that worse quietly, because a promotion and a voucher each approved on their own can take a line below cost without anyone having multiplied the two together. The order of a stack never matters — 30% then 20% is the same as 20% then 30% — but the fact that they multiply always does.
What people use it for
- Checking a sale price in a shop
- Working out a staff or trade discount
- Reading what a "was / now" price really means
- Checking an "extra 20% off sale prices" offer
- Combining a voucher with a sale
- Pricing a promotion and the ticket price it needs
- Planning end-of-season markdowns
- Comparing two stacked offers
- Stacking a trade discount on top of a volume one
- Checking a checkout total against the offer that was advertised
Questions
Multiply the price by the percentage and divide by 100, then subtract. Or multiply the price by (100 − discount) ÷ 100 in one step.
80. You save 20.
No, they multiply. Thirty per cent then twenty per cent is 44% off, not 50%, because the second applies to the already-discounted price.
Subtract the new price from the old, divide by the old, and multiply by 100.
Multiply the full price by (100 − discount) ÷ 100. A 25% cut on 79.99 gives 59.99.
No. Multiplication is commutative, so the final price is the same either way.
Seventy-five per cent off, leaving a quarter of the price. A double discount never adds up to the sum of its parts, and two halves are never free.
Multiply the remaining fractions and subtract from one: 0.7 × 0.8 = 0.56, so the combined discount is 44% off.
Only if the terms allow it. Many are explicitly not combinable, and some apply before rather than after a sale price.
Percentages read as better value on low-priced items; a fixed amount reads better on expensive ones. The arithmetic is identical.
Nearly all of it if margins are thin. A 25% discount on a 40% margin leaves 20%: nearly two thirds of the profit gone.
A price ending just below a round number, like 59.99 rather than 60. The effect is small but consistently measurable.
Only against the same starting price. A 40% discount off an inflated price can cost more than 25% off an honest one.
Yes, but the discounts multiply. Check the effective figure before advertising it.