What Discount Calculator does
Enter the original price and a discount to get the sale price and the saving. Add a second percentage in Extra discount on top and the calculator applies it to the already reduced price, then reports the effective discount across both. Two discounts never add up: 20% off followed by an extra 10% off is 28% off, not 30%, so a 100 item costs 72. An optional tax rate is charged on the discounted amount, giving the total you hand over at the till. Leave the extra discount at 0 and it works as a plain percent off calculator.
Combined discount chart: what two stacked discounts really add up to
The effective discount for common pairs of offers, with what you pay on an original price of 100. Scale the last column to any price: at 52% effective, a 250 item costs 250 × 0.48 = 120.
| First discount | Extra discount | Looks like | Effective discount | You pay on 100 |
|---|---|---|---|---|
| 10% | 10% | 20% | 19% | 81.00 |
| 15% | 10% | 25% | 23.5% | 76.50 |
| 20% | 10% | 30% | 28% | 72.00 |
| 20% | 15% | 35% | 32% | 68.00 |
| 20% | 20% | 40% | 36% | 64.00 |
| 25% | 10% | 35% | 32.5% | 67.50 |
| 25% | 25% | 50% | 43.75% | 56.25 |
| 30% | 10% | 40% | 37% | 63.00 |
| 30% | 20% | 50% | 44% | 56.00 |
| 40% | 10% | 50% | 46% | 54.00 |
| 40% | 20% | 60% | 52% | 48.00 |
| 50% | 10% | 60% | 55% | 45.00 |
| 50% | 20% | 70% | 60% | 40.00 |
| 50% | 50% | 100% | 75% | 25.00 |
| 60% | 20% | 80% | 68% | 32.00 |
| 70% | 10% | 80% | 73% | 27.00 |
Swapping the two columns gives the same result: 10% then 20% is also 28%.
Double discount formula
Sale price = Price × (1 − d1 ÷ 100) × (1 − d2 ÷ 100) Effective discount % = d1 + d2 − (d1 × d2 ÷ 100) Price with tax = Sale price × (1 + tax ÷ 100)
d1 is the first discount and d2 the extra discount, both as percentages. The effective discount is always smaller than d1 + d2 by exactly d1 × d2 ÷ 100. For 20% and 10% the shortfall is 200 ÷ 100 = 2 points, which is why the pair gives 28% rather than 30%. For 40% and 20% it is 800 ÷ 100 = 8 points, giving 52%. The bigger the two discounts, the wider the gap between the headline sum and what you actually get.
Worked examples with stacked discounts and tax
Clearance rail with a further reduction at the till
Original price 59.99, Discount 40%, Extra discount on top 25%
You pay 27.00, You save 32.99, Effective discount 55%
The signs suggest 65% off. The real figure is 55%.
Sale item with a coupon and US-style sales tax
Original price 80, Discount 30%, Extra discount on top 15%, Tax added after discount 8.25%
You pay 51.53, You save 32.40, Effective discount 40.5%, Tax added 3.93
You save is measured before tax: the price falls from 80 to 47.60, then 3.93 of tax is added.
Single discount with 18% tax on top
Original price 1200, Discount 25%, Extra discount on top 0, Tax added after discount 18%
You pay 1,062.00, You save 300.00, Effective discount 25%, Tax added 162.00
Tax on the full 1,200 would have been 216, so the discount also cuts the tax by 54.
Loyalty discount on a marked-down order with 20% tax
Original price 150, Discount 20%, Extra discount on top 10%, Tax added after discount 20%
You pay 129.60, You save 42.00, Effective discount 28%, Tax added 21.60
Single percent off chart for a price of 100
For one discount with no extra offer, the price paid is simply the original price times (100 minus the discount) percent.
| Percent off | You pay on 100 | You save | Multiply any price by |
|---|---|---|---|
| 10% | 90.00 | 10.00 | 0.90 |
| 15% | 85.00 | 15.00 | 0.85 |
| 20% | 80.00 | 20.00 | 0.80 |
| 25% | 75.00 | 25.00 | 0.75 |
| 30% | 70.00 | 30.00 | 0.70 |
| 40% | 60.00 | 40.00 | 0.60 |
| 50% | 50.00 | 50.00 | 0.50 |
| 60% | 40.00 | 60.00 | 0.40 |
| 70% | 30.00 | 70.00 | 0.30 |
| 75% | 25.00 | 75.00 | 0.25 |
When to fill in the tax field and when to leave it at zero
The calculator charges tax on the price after both discounts. That matches how a shop's own price reduction is normally treated: tax is due on what the customer actually pays, so a lower price means less tax.
Use the tax field where shelf prices are quoted before tax, as with sales tax in most of the United States and Canada. Enter your local combined rate and You pay becomes the total at the register.
Leave it at 0 where the ticket price already includes VAT or GST, which is the norm in the UK, the EU, Australia, New Zealand and India. The discount comes off the tax-inclusive price, and adding tax again would count it twice.
One exception: manufacturer coupons and rebates are often taxed on the price before the coupon, because the retailer is reimbursed for the difference. In that case the register total will be slightly higher than the figure shown here.
What this calculator does not do
- Fixed amount off, such as 10 off a 60 order. Convert it to a percentage first (10 ÷ 60 = 16.67%) or subtract it by hand.
- A third stacked discount. Run the first two, then enter the You pay figure as a new Original price with the third discount.
- Working backwards from a sale price to the original price or to the percentage that was taken off.
- Discounts taken off the original price rather than the reduced price. A few retailers do stack this way; if yours does, simply add the two percentages and enter the sum as one discount.
- Currency symbols. Results are plain numbers to two decimal places, so they read the same in any currency.
How to get your result
- 1
Enter the Original price shown on the ticket before any reduction.
- 2
Enter the first Discount as a percentage, for example 40 for 40% off.
- 3
If a further offer applies to the reduced price, enter it in Extra discount on top. Leave it at 0 for a single discount.
- 4
Enter a rate in Tax added after discount if the shelf price excludes sales tax. Leave it at 0 where prices already include tax.
- 5
Read You pay, You save and Effective discount. With tax entered, a Tax added figure appears and You pay includes it.