Stacking is multiplicative, not additive
10% then 10% is 19% off, not 20%. Stacks multiply their “keep” factors, so (1−0.10)×(1−0.10)=0.81 → 19% equivalent.
Compound cuts
Discount Calculator
Use this sale price calculator to find the final price and savings from an original price plus a percent off or fixed amount off. You can also solve backwards for the original price, discount amount, percent off, or sale price, then use the advanced tools for stacked discounts and comparison.
Sale Price Calculator
Enter any two of original price, percent off, amount off, and final sale price. Tax is optional and is added after the discount.
Use either discount field, or enter any two values to solve the rest.
Final price and savings will appear here.
Retail Deal Calculator
Compare common offers such as 2-for-1, 3-for-2, buy one get one 50% off, percent off the second item, and bulk percent-off deals.
Used for second-item and bulk percent deals.
Deal results will appear here.
Advanced stacked discounts, comparison, and target price tools
Multiple (Stacked) Discounts
Example: 10, then 15, then 5. Each discount applies to the reduced price.
Results will appear here.
Final price with stacked \(d_1,\dots,d_n\): \(\displaystyle P_f = P_0 \prod_{i=1}^n (1-d_i)\).
Equivalent single discount: \(\displaystyle D = 1 - \prod_{i=1}^n (1-d_i)\).
Compare Single vs Stacked
Results will appear here.
Stacked equivalent \(D = 1 - \prod(1-d_i)\). We report pre-tax and after-tax prices.
Reverse (Target Price)
Results will appear here.
Needed single discount (pre-tax target): \(\displaystyle D = 1 - \frac{P_f}{P_0}\). If tax \(t\) applies after discount, back out \(P_f = \tfrac{P_{\text{target}}}{1+t}\). If split into \(n\) equal stacked discounts: \(\displaystyle d = 1 - (1-D)^{1/n}\).
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Common Discount Table
Quick final prices before tax for common percent-off discounts.
| Original price | 10% off | 15% off | 20% off | 25% off | 30% off | 40% off | 50% off |
|---|---|---|---|---|---|---|---|
| $20 | $18.00 | $17.00 | $16.00 | $15.00 | $14.00 | $12.00 | $10.00 |
| $50 | $45.00 | $42.50 | $40.00 | $37.50 | $35.00 | $30.00 | $25.00 |
| $100 | $90.00 | $85.00 | $80.00 | $75.00 | $70.00 | $60.00 | $50.00 |
| $200 | $180.00 | $170.00 | $160.00 | $150.00 | $140.00 | $120.00 | $100.00 |
Accuracy and Privacy Notes
- Last updated: June 9, 2026.
- Reviewed for formula accuracy: Starlight Tools uses standard sale price formulas: savings = original - final, percent off = savings / original, and final = original - savings.
- Rounding policy: Calculations use full precision internally and display currency to 2 decimals. Some checkouts round after each coupon, so a real receipt can differ by a cent.
- Privacy: Inputs stay in your browser and are not uploaded by this calculator.
Discount Calculator FAQ
How do I calculate 10%, 20%, 25%, 30%, or 50% off?
Multiply the original price by the discount rate to get the savings, then subtract that savings from the original price. For 20% off $100, savings are $20 and the sale price is $80.
How do I find the original price from a sale price?
If you know the percent off, divide the sale price by 1 - discount rate. If you know the discount amount, add the amount saved back to the sale price.
How do I calculate discount percentage from sale price?
Subtract the sale price from the original price, divide that savings by the original price, then multiply by 100.
Do stacked discounts add together?
No. A 20% discount followed by 10% off is 28% off overall, not 30%, because the second discount applies to the already reduced price.
Does tax apply before or after discount?
Most checkout systems apply tax after eligible discounts are subtracted. This calculator models tax after the discount, but local rules and store policies can vary.
How do fixed amount discounts convert to a percent?
Divide the fixed amount off by the original price and multiply by 100. For example, $20 off $95 is about 21.05% off.
How Discount Rates Work: Single vs. Multiple (Stacked) Discounts
Discounts reduce a list price by a percentage or fixed amount. With a single discount of rate d,
the final price is Pfinal = P0(1 − d). With multiple or stacked discounts
(e.g., 10% then 15%), each discount applies to the price produced by the previous step:
Pfinal = P0 × ∏(1 − di). The equivalent single discount that produces the
same outcome is D = 1 − ∏(1 − di). This is why 10% + 15% is not 25% off; it’s actually 23.5%.
Order, Coupons, and “Up To” Offers
If the retailer specifies the order (e.g., “member 5% then promo 10%”), use it—order only matters when rounding rules or minimum price floors apply. For coupon stacks, check terms: some coupons apply to pre-tax price, others exclude shipping or certain categories. “Up to X%” offers usually mean different items or tiers receive different rates; treat them as separate discounts in the tool.
Taxes, Fees, and Regional Practices (GEO)
Most jurisdictions apply sales tax, VAT, or GST after discounts are taken: Pfinal, tax = Pfinal(1 + t).
In some places, environmental fees, recycling charges, or service fees are added regardless of discounts. If your region includes tax in shelf
prices (common with VAT/GST), the “discount” effectively reduces a tax-inclusive price. Our calculator models tax added after discounts by default.
For international users, note decimal separators (12,5% vs 12.5%) and currency rounding conventions; always enter percentages as whole numbers (e.g., 12.5 for 12.5%).
Business Use: Promotions, Wholesale, and MAP
Merchants often combine a base promotion with a loyalty or payment-method discount. Wholesalers may publish trade discounts (e.g., 30/10) that are explicitly stacked. If you must respect a minimum advertised price (MAP) or margin target, use the Reverse (Target Price) tab: pick a target final (with or without tax), and compute the single or equal stacked discount(s) that hit the goal without violating constraints.
Common Pitfalls
- Adding percentages directly. Stacks compound; do not sum percentages.
- Rounding at the wrong step. Some policies round after each discount; others round only once at checkout. Results can differ.
- Minimum spend / exclusions. A discount might not apply to shipping, subscription items, or already marked-down goods.
- Returns and exchanges. Refunds usually reflect the discounted price; exchanges may reapply active promos differently.
Worked Example
Original price = 250. Discounts: 10%, then 15%, then 5%. Product factor:
(1 − 0.10) × (1 − 0.15) × (1 − 0.05) = 0.90 × 0.85 × 0.95 = 0.72675.
Final pre-tax price = 250 × 0.72675 = 181.6875. Equivalent single discount:
D = 1 − 0.72675 = 27.325%. With 7.5% tax after discounts, final = 181.6875 × 1.075 ≈ 195.82.
When to Use Single vs. Stacked Discounts
If you control the promotion, an equivalent single discount is cleaner for messaging and customer perception. If you’re modeling real-world checkout flows (multiple codes, loyalty tiers, bulk breaks), stacked discounts mirror reality and make it easier to audit edge cases.
Tip for Power Users
To split a required overall discount D into n equal stacked discounts, use
d = 1 − (1 − D)1/n. This is handy when negotiating staged concessions or designing tiered promos.
5 Fun Facts about Discounts
Order only matters with rounding rules
Pure math ignores order, but if a checkout rounds after each discount, swapping “15% then 5%” vs “5% then 15%” can change the price by a few cents.
Sequence quirks
Tax timing flips headline savings
Most places apply tax after discounts, but fixed fees (shipping, environmental) often sit outside the discount. “25% off everything” rarely means 25% off the whole bill.
After the cut
“Up to” is usually far less
A banner shouting “up to 50% off” might average nearer 15–25% across a cart. The true equivalent discount depends on your mix.
Real rate
Margin recovery is asymmetric
A 20% price drop needs more than a 20% hike to recover; you need a 25% markup to get back to a 20% margin. Percentages don’t mirror perfectly.
Percent trap