Percent Off Calculator
Percent off is the language of sales: 20% off, 30% off, half price. The maths behind it is one multiplication, but the traps are real — stacked discounts that do not add, percentages that look bigger than the dollars they save, and tax that arrives at the till. The percent off calculator above handles all of it: enter the price and the percentage, and it shows the sale price, the saving, and the effective discount.
This page explains how percent off works, gives you a full reference table, and works through stacked discounts and real shopping examples.
How Percent Off Works
A percent off tells you what share of the price you do not pay. At 20% off you pay 80% of the price; at 50% off you pay half; at 75% off you pay a quarter. The sale price is the original price × (100 − discount) ÷ 100, and the saving is the original price × discount ÷ 100. For a $100 item at 25% off: you pay 100 × 75 ÷ 100 = $75, and you save 100 × 25 ÷ 100 = $25. The calculator above shows both numbers, plus the effective discount, which matters when discounts are stacked.
Percent Off Reference Table
The table below shows the sale price and the saving for a $100 item at every common percentage, so you can read any sale at a glance.
| Percent off | You pay | You save |
|---|---|---|
| 5% off | $95.00 | $5.00 |
| 10% off | $90.00 | $10.00 |
| 15% off | $85.00 | $15.00 |
| 20% off | $80.00 | $20.00 |
| 25% off | $75.00 | $25.00 |
| 30% off | $70.00 | $30.00 |
| 35% off | $65.00 | $35.00 |
| 40% off | $60.00 | $40.00 |
| 50% off | $50.00 | $50.00 |
| 60% off | $40.00 | $60.00 |
| 70% off | $30.00 | $70.00 |
| 75% off | $25.00 | $75.00 |
| 80% off | $20.00 | $80.00 |
The table scales: for a $200 item, double every figure. For a $50 item, halve them. For a $250 item, multiply by 2.5. A 40% discount on $250 saves $100 and leaves a price of $150 — the same row, scaled.
Worked Examples
Percent off means different dollars on different prices. The table below shows the same percentages on three prices, so you can see how the saving grows with the price.
| Original price | 20% off — you pay | 30% off — you pay | 50% off — you pay |
|---|---|---|---|
| $40.00 | $32.00 | $28.00 | $20.00 |
| $80.00 | $64.00 | $56.00 | $40.00 |
| $150.00 | $120.00 | $105.00 | $75.00 |
| $250.00 | $200.00 | $175.00 | $125.00 |
Check the $150 row: 20% off is 150 × 0.80 = $120; 30% off is 150 × 0.70 = $105; 50% off is $75. And the $40 row: 30% off is 40 × 0.70 = $28. The percentage is the same, but the dollars are not — which is why a big percentage on a cheap item can save less than a small percentage on an expensive one. A 50% discount on a $40 item saves $20, while a 20% discount on a $250 item saves $50.
Stacked Percent Off: The Trap
When two percent discounts apply to the same item, they multiply — they do not add. A 20% discount followed by a 10% discount is 0.80 × 0.90 = 0.72, which is 28% off, not 30%. On an $80 item, the first discount takes it to $64 and the second to $57.60. The table below shows common stacks.
| Stack | Real discount | Price of a $100 item | Price of a $150 item |
|---|---|---|---|
| 10% + 10% | 19% off | $81.00 | $121.50 |
| 20% + 10% | 28% off | $72.00 | $108.00 |
| 25% + 10% | 32.5% off | $67.50 | $101.25 |
| 20% + 25% | 40% off | $60.00 | $90.00 |
| 30% + 20% | 44% off | $56.00 | $84.00 |
| 50% + 20% | 60% off | $40.00 | $60.00 |
Check the 25% + 10% row: 0.75 × 0.90 = 0.675, so the real discount is 32.5% and a $100 item costs $67.50. On a $150 item it costs 150 × 0.675 = $101.25. And the 30% + 20% row: 0.70 × 0.80 = 0.56, so the real discount is 44% and a $150 item costs $84. The gap between adding and multiplying grows with the size of the discounts — at 50% + 50% the real discount is 75%, not 100%.
Percent Off vs Fixed Amount Off
Sometimes you get a choice: 20% off, or $20 off. Which is better depends on the price. On a $100 item they are identical — both save $20. On a $200 item, 20% off saves $40 and beats the $20 fixed discount. On a $50 item, 20% off saves only $10, so the $20 fixed discount wins. The rule is simple: if the price is above $100, the percentage usually wins when the percentage is 20% and the fixed amount is $20 — the break-even point is the fixed amount divided by the percentage. For $20 off versus 20% off, the break-even price is 20 ÷ 0.20 = $100. Above $100, take the percentage; below $100, take the fixed amount.
Percent Off and Tax
Tax applies to the discounted price in most places. A $120 item at 15% off costs $102 before tax; with 8% tax the total is $102 × 1.08 = $110.16. A $200 item at 25% off is $150; with 7% tax the total is $160.50. The calculator has a tax field that shows the tax and the checkout total, so you know the real cost before you reach the till.
Quick Mental Maths for Percent Off
- 10%: move the decimal point one place left. 10% of $80 is $8.
- 20%: double the 10% figure. 20% of $80 is $16, so the price is $64.
- 25%: divide by four. 25% of $80 is $20, so the price is $60.
- 5%: halve the 10% figure. 5% of $80 is $4.
- 15%: add 10% and 5%. 15% of $80 is $8 + $4 = $12, so the price is $68.
- 30%: triple the 10% figure. 30% of $80 is $24, so the price is $56.
Related tools: what saving the difference could grow to with the compound interest calculator, and your salary calculator for the bigger picture of what you earn and spend. The Federal Trade Commission has advice on spotting misleading sale prices and shopping safely.
Quick Reference
Use the discount calculator above with your own numbers, and keep the reference figures below handy while you plan.
| Deal | Sale price ($100 item) | You save |
|---|---|---|
| 10% off | $90.00 | $10.00 |
| 25% off | $75.00 | $25.00 |
| 40% off | $60.00 | $40.00 |
| 50% off | $50.00 | $50.00 |
| 20% then 10% off | $72.00 | $28.00 |
| $20 off | $80.00 | $20.00 |
What to remember
- Sale price is the original price times one minus the discount rate.
- Stacked discounts multiply, they do not add: 20 percent then 10 percent is 28 percent off, not 30.
- Tax is usually charged on the discounted price, not the original.
- Compare the dollars you save, not the percentage — 20 percent off $200 beats 50 percent off $40.
- A fixed discount wins on cheap items; a percentage wins on expensive ones.
Your checklist
- Choose the discount type in the calculator above: percent off, fixed amount or stacked.
- Enter the original price and the discount.
- Add your sales tax rate if you want the checkout total.
- Read the final price, the saving and the effective discount.
- Compare the final total with other stores before buying.
Mistakes to avoid
- Adding stacked discounts instead of multiplying them.
- Forgetting sales tax, which arrives at the till.
- Trusting the crossed-out “was” price without checking the usual price.
- Rounding each step instead of rounding only at the end.
- Confusing “20 percent off” with “pay 20 percent of the price”.
Percent-Off Deals Worth Checking Twice
Not every percent-off deal is equal. Twenty percent off a $200 jacket saves $40, while 50 percent off a $30 gadget saves only $15 — the bigger percentage is not always the bigger saving. Always work out the dollar amount, not just the percentage, before deciding whether a deal is worth it. The calculator above does that in one step: enter the price and the percentage, and the saving is right there.
Stacked discounts deserve a second look too. A store that offers 30 percent off and then another 20 percent off at the register is not giving 50 percent off: the second discount applies to the already-reduced price, so the real cut is 44 percent. Knowing that keeps you from overpaying for a deal that sounds better than it is.
- Compare the dollar saving, not just the percentage.
- Remember stacked discounts multiply; they do not add.
- Check whether the discount covers the whole basket or one item.
- Look for expiry dates and minimum-spend rules in the small print.
Frequently Asked Questions
How do I calculate percent off?
Multiply the original price by one minus the discount rate. For 25% off $100: 100 × 0.75 = $75. The saving is the price times the rate: 100 × 0.25 = $25. The calculator above does it for any price and percentage.
What is 30% off $80?
$56. The saving is 80 × 0.30 = $24, so the sale price is 80 − 24 = $56. For 20% off $80 the price is $64, and for 50% off $80 it is $40.
What is 20% off plus 10% off?
28% off in total, not 30%. The discounts multiply: 0.80 × 0.90 = 0.72, so you pay 72% of the price. On an $80 item that is $57.60, not $56.
How do I calculate percent off with tax?
Apply the discount first, then add tax on the discounted price. A $120 item at 15% off is $102; with 8% tax the total is $102 × 1.08 = $110.16.
Is 50% off always the best deal?
No. 50% off a $40 item saves $20, while 20% off a $250 item saves $50. Compare the dollars you save, not the percentage — and compare the final price including tax with other stores.
How do I find the original price from the sale price?
Divide the sale price by one minus the discount rate. If you paid $75 after 25% off, the original was 75 ÷ 0.75 = $100. If you paid $57.60 after 20% then 10%, the original was 57.60 ÷ 0.72 = $80.
Disclaimer: This calculator is for general information only. Prices, discounts and sales tax rules vary by store and location. Tax is usually charged on the discounted price, but some places tax the original price — check your receipt and local rules.