Discount Calculator — Find Sale Price, Discount Rate & Original Price
Jun 23, 2026
Ever stared at a product page showing "Original: $50.00 → Sale: $35.00" and struggled to work out the percentage in your head? Or wondered what the original price was when you only know the sale price and the discount rate? This guide covers the three discount formulas you actually need — plus a common stacked-discount mistake that costs people money.
Enter any two values — sale price, discount rate, or original price — and the third is calculated instantly. Free, no sign-up.
Open Discount Calculator →The 3 Core Formulas
Every discount calculation comes down to one of three formulas.
- Sale price = Original price × (1 − Discount rate) — Use when you know the rate and want the final price. Example: $50.00 at 30% off → $50.00 × 0.7 = $35.00
- Discount rate (%) = (Original − Sale) ÷ Original × 100 — Use when you know both prices and want the percentage. Example: $50.00 down to $35.00 → (50 − 35) ÷ 50 × 100 = 30%
- Original price = Sale price ÷ (1 − Discount rate) — Reverse-calculate the original price. Example: $35.00 after 30% off → $35.00 ÷ 0.7 = $50.00
How to Use the Calculator — 2 Steps
- Enter any two known values — In the discount calculator, fill in two of the three fields: original price, discount rate, or sale price. The missing field calculates automatically.
- Read the result — The calculator shows the sale price, the discount amount saved, and the effective discount rate all at once. Change any number and it recalculates instantly.
The Stacked-Discount Trap — 30% + 10% is NOT 40%
When coupons stack on top of promotional discounts, many shoppers (and even retailers) assume the rates simply add up. They don't — discount rates multiply, they don't add.
| Scenario | Calculation on $100 | Effective rate |
|---|---|---|
| 30% off only | $100 × 0.7 = $70.00 | 30% |
| 30% + 10% added (wrong: sum to 40%) | $100 × 0.6 = $60.00 (incorrect) | 40% (myth) |
| 30% then 10% extra (correct: multiply) | $100 × 0.7 × 0.9 = $63.00 | 37% |
Here is why: a 30% discount leaves 70% of the price. A further 10% discount takes 90% of what remains. Multiply the two retention rates: 0.7 × 0.9 = 0.63, so the effective discount is 1 − 0.63 = 37%, not 40%. The 3-percentage-point gap widens noticeably on high-ticket items. To verify stacked discounts, run the calculator twice in sequence — apply the first discount, then enter that result as the new price and apply the second.
Pair It With the VAT Calculator
Once you have your sale price, you may need to add or strip VAT for invoices and receipts. The VAT calculator handles that in one step — supply amount, tax, and total all at once. A quick workflow: use the discount calculator to set your sale price, then pass that figure to the VAT calculator to get the tax-inclusive amount for your quote or price tag.
Enter two values. Get the third. Free.
Calculate Now →Frequently Asked Questions
Q. What is the discount rate formula?
Discount rate (%) = (Original price − Sale price) ÷ Original price × 100. For example, if an item costs $50 and sells for $35, the discount rate is (50 − 35) ÷ 50 × 100 = 30%. The calculator does this automatically when you enter both prices.
Q. Can I reverse-calculate the original price?
Yes. If you know the sale price and discount rate, the original price = sale price ÷ (1 − discount rate). Leave the original-price field blank in the calculator and it will fill it in for you.
Q. Does stacking a 30% and a 10% discount really give only 37%?
Correct. The second discount applies to the already-reduced price, not the original. The math is 0.7 × 0.9 = 0.63, meaning 63% of the original price remains — a 37% total discount, not 40%.
Q. Should I use the VAT-inclusive or exclusive price when calculating discounts?
The discount formula works the same either way, but you must be consistent — do not mix a VAT-inclusive original price with a VAT-exclusive sale price. Use the VAT calculator to convert between the two before plugging numbers in.