How does the discount calculator work?

For a straightforward discount: sale price = original price × (1 − discount% ÷ 100). Amount saved = original price − sale price. For the reverse mode: % off = (original − sale) ÷ original × 100.

Why is a stacked discount not the same as adding the percentages?

Each successive discount applies to the already-reduced price, not the original. For example, 20% off then 10% off gives an effective saving of 28%, not 30%. The formula is: final price = original × (1 − d1/100) × (1 − d2/100) × ...

How do I calculate 30% off a price?

Multiply the price by 0.70 (which is 1 − 30/100). A £50 item at 30% off costs £50 × 0.70 = £35, saving £15. Enter 50 as the original price and 30 as the discount in forward mode.

How do I work out the percentage off if I only know the two prices?

Subtract the sale price from the original, divide by the original, then multiply by 100. An item that dropped from £80 to £60 is (80 − 60) ÷ 80 × 100 = 25% off. Use the reverse mode and enter both prices.

Does the order of stacked discounts change the final price?

No. Because the discounts are multiplied together, 20% then 10% gives the same final price as 10% then 20% — both reach 72% of the original. Order only matters for which intermediate price you see along the way.

What's the difference between a discount and a coupon stacked on a sale?

They are usually multiplicative, not additive. A 25%-off sale plus a 10%-off coupon does not equal 35% off — it equals 1 − (0.75 × 0.90) = 32.5% off. Use stacked mode to get the true combined figure.

Completely. All calculations run locally in your browser using JavaScript. No prices or percentages are sent to any server.

Discount & Sale Price Calculator

Discount and sale price calculator

Three discount tools in one page, for shoppers comparing deals, retailers pricing promotions, and anyone checking whether a “stacked” offer is as good as it sounds. Pick a mode, enter your numbers, and the sale price, amount saved and effective percentage off appear instantly.

How it works

Forward — given an original price and a discount, the sale price is original × (1 − discount ÷ 100) and the amount saved is original − sale.
Reverse — given the original and the sale price, the percentage off is (original − sale) ÷ original × 100.
Stacked — each discount is applied to the already-reduced price in turn: final = original × (1 − d1 ÷ 100) × (1 − d2 ÷ 100) × (1 − d3 ÷ 100). The effective percentage off is (original − final) ÷ original × 100. The tool compares this against the naive sum of the percentages so you can see why stacking gives less than the headline numbers suggest.

Example

A £200 coat is 20% off, then a member coupon takes a further 10% off the reduced price. Stacking gives 200 × 0.80 × 0.90 = £144, a saving of £56 — an effective 28% off, not the 30% you would get by adding 20% and 10% together.

Discounts applied	Effective % off	£200 becomes
10% + 10%	19%	£162.00
20% + 10%	28%	£144.00
25% + 20%	40%	£120.00
50% + 50%	75%	£50.00

All calculations happen instantly in your browser. No data is uploaded or stored.