How this calculator works
This extends the plain discount calculator to up to four sequential percentage discounts, an optional flat-amount coupon, and sales tax, for sales that stack a storewide discount with a clearance markdown, a loyalty percentage, and a promo code. Leave any discount field at 0 to skip it — with only the first field filled in, this reduces to the same single-discount math as the discount calculator.
Two things trip people up. First, stacked percentages never simply add together: 20% off followed by 10% off removes 28% total, not 30%, because the second discount applies to the already-discounted price. Second, when a flat-dollar coupon is involved, the order it's applied in changes the final price — a coupon taken off before the percentage discounts shrinks a smaller base, while one taken off after removes a fixed amount regardless of how big the percentage discounts were. This calculator lets you choose which happens first and shows the difference.
The formula
Each active discount: running price = running price × (1 − discount ÷ 100), applied in orderFlat coupon: running price = max(0, running price − coupon), applied before or after the percentage discounts as selectedFinal price = (price after discounts and coupon) × (1 + tax rate ÷ 100)Percentage discounts alone are commutative — applying 15% then 25% gives the same result as 25% then 15%, since multiplying factors together doesn't depend on order. A flat coupon breaks that symmetry, because subtracting a fixed amount from a different base changes what the percentages that follow (or preceded) it apply to.
Worked example: two discounts, a coupon, and tax
- Start with a $200 item: 20% off, then an extra 10% off, then a $15 flat coupon applied after the percentage discounts, plus 8% sales tax.
- After 20% off: 200 × 0.80 = $160.00. After the extra 10% off: 160 × 0.90 = $144.00.
- After the $15 coupon (applied after the percentage discounts): 144.00 − 15.00 = $129.00. This is the price before tax — total saved is 200 − 129 = $71.00, an effective 35.5% discount.
- Sales tax is added last, on the discounted price: 129.00 × 1.08 = $139.32, the actual amount charged at checkout.
Frequently asked questions
Why don't stacked percentage discounts just add up?
Because each discount after the first applies to a smaller, already-discounted price. Losing 10% of a $160 price is $16, not 10% of the original $200 ($20), so two discounts of 20% and 10% combine to a 28% effective discount, always a little less than the sum of the individual percentages.
Does it matter whether the coupon is applied before or after the percentage discounts?
Yes. On a $100 item with one 50% discount and a $20 flat coupon: applying the coupon first gives (100 − 20) × 0.5 = $40, while applying it after gives (100 × 0.5) − 20 = $30. The larger the percentage discount, the bigger this gap gets, so it's worth checking which order a retailer actually uses.
Is sales tax calculated before or after the discounts?
This calculator applies tax last, to the price after every discount and the coupon — the common retail convention, since store discounts and store coupons usually reduce the taxable sale price. Manufacturer coupons are taxed differently in some US states (the pre-coupon amount stays taxable); check your local rules if that applies to your purchase.
What if I only have one discount, or none at all?
Leave the other discount fields at 0 — they're skipped entirely, and the calculator reduces to a single discount, or to just the coupon and tax if all four percentage fields are left at 0.
Does the order of the percentage discounts themselves matter?
No — applying a 15% discount then a 25% discount gives exactly the same final price as 25% then 15%, since multiplying the same two factors together in either order produces the same result. Order only matters once a flat coupon is mixed in.