# How to Calculate a Discount (and Work Backwards from the Sale Price)

> Percentage-off maths is simple until you need the original price from a discounted one. Here's both directions, with examples retailers can use today.

- URL: https://www.pyalm.com/blog/how-to-calculate-discounts
- Author: Fadhil Abdulla
- Category: Pyalm Books
- Published: 2026-06-17
- Updated: 2026-06-17

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## Forward: price to sale price

To apply a discount, multiply the original price by the discount percentage and subtract. Discount amount = original price × discount % ÷ 100. A AED 200 item at 15% off saves AED 30, giving a AED 170 sale price. The free [Discount Calculator](https://www.pyalm.com/free-tools/discount-calculator) shows the amount, the final price, and the saving instantly.

## Backwards: sale price to original price

This is where mistakes happen. To recover the original price from a discounted one, divide by (1 − discount/100). For 20% off, divide the sale price by 0.8 — you do not add 20% back.

## Watch your margins

Discounts come straight off your contribution margin. A 20% discount on a product with a 40% margin wipes out half your profit on that sale. Before running a promotion, check what the discount does to profitability with the [Profit Margin Calculator](https://www.pyalm.com/free-tools/profit-margin-calculator).

## Keep promotions under control

- Decide the maximum discount your margin can absorb.
- Prefer time-boxed offers over permanent price cuts.
- Track the net effect on revenue, not just units sold.

[Use the free Discount Calculator](https://www.pyalm.com/free-tools/discount-calculator) | [Try the Profit Margin Calculator](https://www.pyalm.com/free-tools/profit-margin-calculator)