How do I calculate the discount percentage from two prices?

Subtract the sale price from the original, divide by the original, then multiply by 100. From 250 down to 175 is (250 − 175) ÷ 250 × 100 = 30 per cent.

How do two discounts combine?

Multiply the remaining fractions. Thirty per cent then twenty per cent leaves 0.7 × 0.8 = 0.56 of the price, which is 44 per cent off — not 50.

Is the discount applied before or after tax?

Normally before. In most sales-tax systems the tax is calculated on the discounted price, so the saving on the total is slightly larger than the discount on the item alone.

Discount Calculator

Quick answer

Sale price equals the original price multiplied by (1 − discount ÷ 100). A 30% discount on 250 gives 250 × 0.7 = 175, a saving of 75.

Sale price and saving

Original price

Discount (%)

Second discount (%)

Stacked offers apply to the already-reduced price.

You pay

175.00

You save

75.00

Effective discount

30.0 %

The arithmetic is simple; the traps are in the framing. Retailers present the same reduction in whichever way sounds largest, and stacked offers are almost never what the signage implies.

The other thing worth checking is what the original price was actually charged at. A discount from a price nobody paid is not a discount, and several jurisdictions now require the reference price to be the lowest applied in the preceding 30 days.

Stacked discounts never add up

An extra 20 per cent off an item already reduced by 30 per cent does not give 50 per cent off. The second reduction applies to the already-reduced price, so the combined discount is 44 per cent.

The general rule: multiply what remains. Thirty per cent off leaves 0.7, a further 20 per cent leaves 0.8, and 0.7 × 0.8 = 0.56 — meaning 44 per cent off. The more discounts you stack, the wider the gap from naive addition.

Buy-one-get-one and percentage equivalents

Buy one get one free is 50 per cent off only if you wanted two. Buy two get one free is 33 per cent off across three items. Half price on the second item is 25 per cent off the pair.

Converting every offer to an effective per-unit price is the only way to compare them, especially when pack sizes differ. A multibuy is worse value than a straight discount whenever it pushes you past what you would otherwise buy.

Frequently asked questions

How do I calculate the discount percentage from two prices?: Subtract the sale price from the original, divide by the original, then multiply by 100. From 250 down to 175 is (250 − 175) ÷ 250 × 100 = 30 per cent.
How do two discounts combine?: Multiply the remaining fractions. Thirty per cent then twenty per cent leaves 0.7 × 0.8 = 0.56 of the price, which is 44 per cent off — not 50.
Is the discount applied before or after tax?: Normally before. In most sales-tax systems the tax is calculated on the discounted price, so the saving on the total is slightly larger than the discount on the item alone.

Related calculators

Percentage CalculatorWork out a percentage of a number, add or subtract a percentage, and see why a rise then an equal fall never returns to the original figure.Tip CalculatorWork out the tip and the total, split it between any number of people, and check customary tipping rates before you travel.Risk Assessment Matrix CalculatorScore a hazard by likelihood and severity on a 5×5 matrix, see which action band it falls into and what each band requires.Unit Price CalculatorCompare two products by price per unit when the pack sizes differ, and see how much the larger pack really saves.

Updated 2026-09-20 · all calculators. Results are estimates for guidance, not professional advice.