What this discount calculator does
Enter a price and a discount and this tool gives you the sale price, the amount saved, the real percentage off, and — when you need it — the price after sales tax. It handles the four everyday questions shoppers and shopkeepers actually ask: what will I pay, what was the original price, what is the true percentage off, and what happens when discounts are stacked on top of each other.
Two things trip people up most often, and this calculator is built around getting both right: stacked discounts compound, they do not add, and a discount is normally applied before tax, not after.
The six modes
- Percent off — original price and a discount % → sale price and amount saved.
- Amount off — original price and a flat money amount → sale price and the equivalent %.
- Find discount % — original and sale prices → the percentage off (or a markup if the price rose).
- Find original — sale price and a discount % → the recovered list price.
- Stacked discounts — 1–5 successive rates → the sale price and the single equivalent discount.
- Discount + tax — original price, a discount % and a tax % → the net price and the final price after tax.
BOGO (buy-one-get-one-free) and 2-for-1 deals require knowing the prices of multiple items. For a simple BOGO where the second item is free, the effective discount on the pair is 50%. When the second item is a different price, treat the free item as 100% off and the paid item as 0% off, then divide the total savings by the combined price to find the effective rate — or use the Stacked discounts mode with the individual rates applied per item.
The formulas, in plain terms
- Sale price: original × (1 − discount ÷ 100).
- Amount saved: original − sale = original × discount ÷ 100.
- Discount % from two prices: (original − sale) ÷ original × 100.
- Original from a sale price: sale ÷ (1 − discount ÷ 100).
- Stacked (successive): original × (1 − d1 ÷ 100) × (1 − d2 ÷ 100) × … — multiply the factors.
- Discount then tax: original × (1 − discount ÷ 100) × (1 + tax ÷ 100).
Worked examples
The table below is produced by the same engine that powers the calculator above, so it can never drift from the math — one row per mode.
| Mode | Inputs | Result |
|---|---|---|
| Percent off | $90, 20% off | Sale $72.00, saved $18.00 |
| Amount off | $95, $20 off | Sale $75.00, ≈21.05% |
| Find discount % | $80 → $60 | 25% off, saved $20.00 |
| Find original | $72 after 20% | Original $90.00 |
| Stacked | $100, 20% then 10% | Sale $72.00, 28% effective |
| Discount + tax | $100, 20% off, 8% tax | Net $80.00, final $86.40 |
The stacked-discount trap: discounts compound, they don't add
“20% off, then an extra 10% off” feels like 30% off. It is not. The second discount applies to the already-reduced price, so $100 becomes $80, and 10% off $80 is $72 — an effective 28% discount, not 30%. The naive additive answer ($70) is always too generous. The gap widens as the rates grow: 50% then 50% is 75% off, never 100%.
| Discounts | Naive sum | True effective | Sale on $100 |
|---|---|---|---|
| 20% then 10% | 30% | 28.00% | $72.00 |
| 18% then 12% | 30% | 27.84% | $72.16 |
| 10% + 15% + 5% | 30% | 27.32% | $72.67 |
| 50% then 50% | 100% | 75.00% | $25.00 |
For exactly two discounts there is a tidy shortcut: the single equivalent discount is d1 + d2 − (d1 × d2) ÷ 100. For three or more, just multiply the surviving factors (1 − di ÷ 100) together — the pairwise shortcut is only exact for two.
Why discount is applied before tax
Under the standard US and India retail rule, the store discounts the price first, then charges sales tax, VAT or GST on the lower, discounted amount — so the discount also shrinks the tax you pay. This calculator follows that convention: $100 with 20% off and 8% tax is $80 net, then $86.40 final. A few coupon types and jurisdictions tax the pre-discount price instead; this tool does not model that case.
The edge cases this calculator handles
A 0% discount leaves the price unchanged; a 100% discount makes the item free. A discount entered above 100% is clamped to 100, so the sale price never goes negative. Reversing an original price is mathematically undefined at a 100% discount (it would divide by zero) and is guarded rather than shown as infinity. Finding the discount % from a zero original price is also guarded. And if you enter a sale price higher than the original, the result is reported as a markup — a price increase — instead of being hidden.
Frequently asked questions
How do I calculate a discount on a price?+
Multiply the original price by the discount rate as a decimal to get the amount saved, then subtract it. For example, 20% off a $90 item is 90 × 0.20 = $18 saved, so you pay 90 − 18 = $72. Equivalently, you pay (100 − 20)% = 80% of the price: 90 × 0.80 = $72.
How do I find the original price from a sale price?+
Divide the sale price by (1 − discount ÷ 100). If an item costs $72 after a 20% discount, the original price was 72 ÷ (1 − 0.20) = 72 ÷ 0.80 = $90. This reverse calculation is undefined at a 100% discount because you would be dividing by zero.
How do I find the discount percentage from two prices?+
Subtract the sale price from the original, divide by the original, and multiply by 100. From $80 down to $60, the discount is (80 − 60) ÷ 80 × 100 = 20 ÷ 80 × 100 = 25%.
Are two successive discounts the same as adding them together?+
No — this is the most common discount mistake. 20% off then 10% off is NOT 30% off. The discounts compound multiplicatively: $100 × 0.80 × 0.90 = $72, which is a 28% effective discount, not 30%. Each later discount applies to the already-reduced price, so stacked discounts always save less than their simple sum.
What single discount equals 20% then 10%?+
28%. For exactly two discounts d1 and d2 the equivalent single discount is d1 + d2 − (d1 × d2) ÷ 100 = 20 + 10 − (20 × 10) ÷ 100 = 30 − 2 = 28%. For three or more discounts, multiply the (1 − di ÷ 100) factors together instead of chaining this shortcut.
Is the discount applied before or after tax?+
By the standard US and India retail convention, the discount is applied first and the sales tax, VAT or GST is then charged on the discounted (net) price. For example, 20% off $100 with 8% tax is 100 × 0.80 = $80, then 80 × 1.08 = $86.40. This calculator follows discount-before-tax.
How do I calculate a fixed amount off, like $20 off?+
Just subtract the amount: $95 − $20 = $75. To express it as a percentage, divide the amount off by the original price and multiply by 100: 20 ÷ 95 × 100 ≈ 21.05%. The same money amount is a bigger percentage on a cheaper item.
Does the order of stacked discounts matter?+
No. Because the discounts multiply, 20% then 10% gives exactly the same final price as 10% then 20% — both reach $72 on a $100 item. Multiplication is commutative, so the sequence never changes the total you pay.
What does a discount over 100% mean?+
It is not meaningful for a normal sale — a discount above 100% would push the price below zero. This calculator clamps the discount to a maximum of 100% (which makes the item free) and never shows a negative price.
Why does the calculator show a negative or markup result sometimes?+
If you enter a sale price that is higher than the original price in reverse mode, the result is a negative discount — that is a markup or surcharge, not a discount. The calculator surfaces it with a warning so you can see the price actually went up.
Can I use this discount calculator in any currency?+
Yes. A discount is a pure percentage, so the math is identical in dollars, rupees, euros, pounds or yen. Use the currency selector to display your figures; only the formatting changes, never the formula.
How much do I save with a “buy more, save more” stack of three discounts?+
Multiply all three factors. For 10%, 15% and 5% off, you pay 0.90 × 0.85 × 0.95 = 0.72675 of the original, so the effective discount is about 27.3% — again less than the simple sum of 30%, because each discount applies to the already-reduced price.
What are fake discounts or fictitious reference prices?+
A fake discount is one where the retailer inflates the “original” or “was” price so that the percentage off looks larger than it really is. Under the US FTC Guides Against Deceptive Pricing, a reference price is only legitimate if the item was genuinely sold at that price for a reasonable period. Perpetual “sale” prices, artificial strikethrough MSRPs set purely to manufacture a large discount, and limited-time offers that never expire are all deceptive pricing tactics. To protect yourself, compare the actual sale price across stores rather than trusting the stated percentage off.
What are the different types of discounts in business?+
Discounts generally fall into three categories. A quantity (or volume) discount rewards buyers who purchase in bulk — the per-unit price falls as the order size grows. A trade discount is offered by a manufacturer or wholesaler to a distributor or retailer as a reduction from the listed price, not to the end consumer directly. A promotional (or consumer) discount is what most shoppers see: a percentage or amount off the retail price to drive sales. This calculator handles promotional discounts; trade and quantity discounts use the same underlying math but apply to different parties in the supply chain.
Sources
- calculator.net — Discount Calculator: percent-off and fixed-amount-off worked examples (10% of $45 = $4.50 → $40.50; $95 − $20 = $75)
- Byju's — Discount Formula: Selling Price = List Price × ((100 − discount%) ÷ 100); List Price = Selling Price × (100 ÷ (100 − discount%))
- PrepInsta — Successive Discount Formula: Total discount = (x + y − xy ÷ 100)%; 10% then 20% on ₹1000 → 28% → ₹720
- Omnicalculator — Discount: discounted price = original − (original × discount ÷ 100); reverse discount-% and reverse original-price methods
Formula and data last reviewed by the TheCalculatorVault team on 26 June 2026. Figures are for general information, not professional advice.
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