Discount Calculator
Find the final price, total savings, and cost after any discount percentage, additional discount, sales tax, and quantity are applied together.
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Enter your values above to see the results.
Tips & Notes
- ✓Stacked discounts always produce an effective rate less than their sum — 20% off then 15% off equals 32% effective, not 35%.
- ✓The order of stacked discounts does not affect the final price — 30% then 10% produces the same result as 10% then 30%.
- ✓Compare deals by calculating the final price, not the discount percentage — a 40% off item at $120 original costs $72; a 50% off item at $130 costs $65.
- ✓Sales tax is applied after all discounts, not before — a store adding tax before the discount is applying it incorrectly and charging you more.
- ✓Bulk quantity discounts compound with percentage discounts — use the total cost output to compare buying 3 at 20% off versus 1 at 40% off.
- ✓Percentage discounts on high-priced items produce more dollar savings than the same percentage on low-priced items — always calculate the dollar amount, not just the rate.
Common Mistakes
- ✗Adding stacked discount percentages instead of compounding them — 25% off plus 15% off is 36.25% effective, not 40%.
- ✗Comparing discounts by percentage alone without checking the original price — a 50% discount from an inflated original price may be worse than 30% off a fair price.
- ✗Not including sales tax in the final cost comparison — a $200 item after discount in an 8% tax state costs $216, not $200.
- ✗Applying the coupon discount to the original price instead of the sale price — additional coupon discounts always apply to the already-discounted price.
- ✗Forgetting to multiply by quantity before comparing deals — a bulk purchase with a smaller discount may cost more total than individual purchases at a higher discount.
- ✗Ignoring the per-unit price when buying in bulk — calculate cost per unit after all discounts to verify the bulk price is actually better than the single-unit alternative.
Discount Calculator Overview
A discount calculator applies one or two successive discounts to an original price, adds sales tax, and multiplies by quantity to show the complete final cost. It also shows the effective combined discount when two discounts are stacked — which is always less than their sum.
Understanding how stacked discounts work prevents overestimating savings and helps identify the best deal when promotions are expressed in different formats.
What each field means:
- Original Price — the listed or regular price before any discount is applied
- Discount — the first discount percentage; applied directly to the original price
- Additional Discount — a second discount applied to the already-discounted price, not the original
- Sales Tax — the applicable tax rate added after all discounts are applied
- Quantity — the number of units purchased; multiplies the final discounted price
What your results mean:
- Sale Price — the price after the first discount, before the additional discount and tax
- Price After Tax — the final price per unit including all discounts and sales tax
- You Save — the total dollar amount saved from the original price per unit
- Effective Discount — the true combined discount percentage when both discounts are stacked
- Total Cost — the complete amount paid for all units after all discounts and tax
- Total Saved — total savings across all units compared to the original price times quantity
Example — $299 original price, 30% discount, 10% additional discount, 8% tax, 2 units:
Original price: $299.00 After 30% discount: $299 x 0.70 = $209.30 After additional 10%: $209.30 x 0.90 = $188.37 Sales tax (8%): $188.37 x 1.08 = $203.44 Per unit total: $203.44 Quantity 2: total cost $406.88 Total saved vs original (2 x $299 = $598): $191.12 Effective discount: 37% (not 40% — stacked discounts compound, not add)
EX: Why stacked discounts are less than their sum 30% off then 10% off: effective discount = 1 - (0.70 x 0.90) = 37% 10% off then 30% off: effective discount = 1 - (0.90 x 0.70) = 37% Simply adding: 30% + 10% = 40% (wrong) The order does not matter but the result is always less than the sum. On a $1,000 item: 37% effective saves $370, not $400.
Effective combined discount by first and second discount:
| First Discount | +10% additional | +15% additional | +20% additional |
|---|---|---|---|
| 20% | 28% effective | 32% effective | 36% effective |
| 30% | 37% effective | 40.5% effective | 44% effective |
| 40% | 46% effective | 49% effective | 52% effective |
Total cost by quantity and discount — $299 original, 8% tax:
| Discount | Qty 1 | Qty 3 | Qty 5 |
|---|---|---|---|
| 20% off | $258.14 | $774.43 | $1,290.72 |
| 30% off | $226.37 | $679.12 | $1,131.87 |
| 40% off | $193.61 | $580.82 | $968.04 |
Stacked discounts are a common retail pricing tactic. A store advertising 30% off with an additional 10% off coupon generates more perceived savings than the actual 37% effective discount — because customers naturally add the percentages and expect 40% off. Always calculate the effective discount on the original price to understand what a deal is truly worth.
Frequently Asked Questions
Stacked discounts apply sequentially, not additively. The second discount applies to the already-reduced price, not the original. A 30% discount on a $100 item produces $70. A subsequent 20% discount applies to $70, producing $56 — not $50 as a combined 50% would suggest. The effective combined discount is 44%, not 50%. Formula: Effective discount = 1 - (1 - d1) x (1 - d2). For 30% and 20%: 1 - (0.70 x 0.80) = 1 - 0.56 = 44%. This is why advertised stacked discounts always produce slightly less savings than the sum of the percentages.
No — the order of applying two percentage discounts produces the same final price regardless of sequence. Applying 30% then 20% on a $100 item: $100 x 0.70 x 0.80 = $56. Applying 20% then 30%: $100 x 0.80 x 0.70 = $56. Multiplication is commutative, so the order never affects the outcome. This means a store advertising "30% off, then take an additional 20%" and one advertising "20% off, then take an additional 30%" produce identical prices — choose based on other factors like return policy, availability, and total cost including shipping.
Effective discount = 1 - (1 - first discount) x (1 - second discount). Example: 25% off and 15% additional off: 1 - (1 - 0.25) x (1 - 0.15) = 1 - (0.75 x 0.85) = 1 - 0.6375 = 36.25% effective. The effective discount is always less than the sum (25% + 15% = 40%) because the second discount applies to a smaller base. The gap between the sum and the effective discount grows as the individual discounts grow — two 50% discounts produce a 75% effective discount, not 100%.
Sales tax should be calculated on the final discounted price, after all discounts are applied. This is both mathematically correct and legally required in most jurisdictions — tax applies to the actual transaction price, not the pre-discount price. A $300 item with 30% discount and 8% tax: discounted price $210, tax $16.80, total $226.80. If tax were incorrectly applied before the discount: tax on $300 = $24, then 30% off $324 = $226.80 — the same result in this case because tax and discount are multiplicative, but the proper method is discount first, then tax.
To compare a percentage discount to a dollar amount discount, convert both to the same format. A 25% discount on a $200 item saves $50. A $45 flat discount on the same item saves $45 — the percentage is better. On a $150 item, 25% saves $37.50, making the $45 flat discount better. The crossover point where $45 flat equals 25% off is $45 / 0.25 = $180 — above this price, the percentage discount wins; below it, the dollar amount wins. Retailers sometimes offer both formats on different items to create the perception of generous discounts across their product range.
Always compare final price after all discounts and applicable taxes — not discount percentages. Steps: apply all discounts to the original price at each store, add applicable sales tax for each location (varies by state and city), add any shipping or handling costs, then compare final delivered prices. A 40% discount at a store in a 10% tax state may cost more than a 35% discount at a store in a 0% tax state depending on price level. For high-value purchases, the combination of discount rate, tax rate, and shipping often matters more than any single variable.