Discount Calculator
See the sale price, how much you save, and how stacked coupons change the deal — with a quick compare of other discount levels.
Calculate
Sale price
The formula
A percentage discount multiplies the original price by the remaining share (1 − discount%). A second coupon multiplies again. Sales tax, when entered, applies to the discounted price.
Worked example
- Original $100, discount 20%
- Sale = $100 × (1 − 0.20) = $80
- Saved = $100 − $80 = $20 (effective 20% off)
Result: Sale $80 · you save $20
How the discount is applied
Percent-off deals reduce the remaining price. Stacked coupons multiply; tax is usually charged on the discounted amount.
Single percentage off
Sale price = original × (1 − d/100). A 25% discount leaves 75% of the original. Savings are original × d/100.
Stacked discounts are multiplicative
Two successive discounts multiply remaining factors. 20% off then 10% off → 0.80 × 0.90 = 0.72 of original (28% total off), not 30%. Use “Extra % off (after)” for the second coupon.
Sales tax
In many places, sales tax applies to the discounted price. Enter a tax rate to see the checkout total after the deal.
What we do not model
No BOGO logic, fixed-amount coupons ($10 off), shipping, or loyalty points. Convert those to an equivalent percentage first if you want a single % input.
Interesting facts
Black Friday math
A 20% off plus another 10% off is not 30% off — successive discounts multiply. After 20%, only 80% remains; 10% of that leaves 72% of the original price.
Markup vs margin
A 50% markup on cost is not a 50% profit margin. Margin divides profit by selling price; markup divides by cost.
Anchor prices
Retailers often show a higher “was” price to frame the deal. Compare the final checkout total, not only the flashy percentage.
Sales tax after discount
In many U.S. states, sales tax applies to the discounted price. Always check whether tax is included in the advertised total.
Coupon stacking rules
Store and manufacturer coupons may or may not combine. Read the fine print — “cannot be combined” is common.
Frequently asked questions
Multiply the original price by (1 − discount%/100). Example: $100 with 20% off → $80. The calculator also shows dollars saved and an effective discount when coupons stack.
Switch to “Discount %” mode and enter the original and sale prices. Or compute saved ÷ original × 100.
No. Apply them one after another (multiply the remaining fractions). Use Extra % off for the second coupon — 15% then 10% leaves 0.85 × 0.90 = 76.5% of the original.
Optionally. Open Coupon and tax, enter your local rate, and we apply tax to the discounted price for a checkout-style total.
Subtract the fixed amount from the price first (or after a %-off, depending on store rules), then optionally convert the combined deal to an equivalent percentage.
References
- Percentage — NIST SI education Authoritative guidance on expressing quantities; percent is a ratio × 100.
- Sales tax basics Federal context for sales tax; actual rates and bases are set by states and localities.
- Consumer shopping tips Practical guidance for evaluating online offers and checkout totals.