Discount Calculator — Percent Off, Coupons & Tax
Calculate checkout totals with stacked discounts, fixed coupons, quantity, tax, and shipping; find percent off, reverse an original price, or compare two deals.
Sale checkout calculator
Percentage discounts apply in sequence, followed by one fixed order coupon, tax, and shipping.
Find the discount percentage
Compare an original price with a lower sale price.
Find the original price
Reverse a known sale price and percentage discount.
Compare two sale offers
Use the same item price, quantity, and tax rate while varying discounts, coupons, and shipping.
Deal A
Deal B
Original vs. discounted checkout
Calculation breakdown
Discount calculator with tax and coupons
Calculate a complete sale checkout from the original price, quantity, one or two percentage discounts, a fixed order coupon, sales tax, and shipping. The result separates merchandise savings from tax and delivery charges so a large advertised discount is not confused with the final amount paid.
Percent off formula
For one discount, sale price equals original price × (1 − discount rate). A $100 item at 20% off costs $80 and saves $20. To find the percentage from two prices, divide the savings by the original price and multiply by 100.
How stacked discounts work
Successive percentage discounts multiply instead of adding. A 20% discount followed by an extra 10% leaves 80% × 90% = 72% of the original price, so the effective discount is 28%, not 30%. This workspace then applies a fixed order coupon to the revised subtotal.
Reverse discount calculator
To recover an original price, divide the sale price by one minus the discount rate. If a $70 sale price reflects 30% off, the original price was $70 ÷ 0.70 = $100. A 100% discount cannot be reversed because many original prices could produce a free item.
Compare coupons and sale offers
Compare two deals using the same item price, quantity, and tax rate while changing percentage discounts, fixed coupons, and shipping. The lower checkout total is highlighted, while merchandise savings and effective discount remain visible for both offers.
Tax and shipping assumptions
The calculator applies tax to the merchandise subtotal after the entered discounts and coupon, then adds shipping without taxing it. Real taxable amounts vary by location, product, coupon sponsor, and shipping rules, so verify the checkout or local guidance for important purchases.
Discount formulas
| Question | Formula |
|---|---|
| Price after one discount | Original × (1 − discount rate) |
| Successive discounts | Original × (1 − rate 1) × (1 − rate 2) |
| Percent off | (Original − sale) ÷ original × 100 |
| Original price | Sale ÷ (1 − discount rate) |
| Effective discount | Total merchandise savings ÷ original subtotal × 100 |
Frequently asked questions
Is 20% off plus 10% off equal to 30% off?
No. The second discount applies to the already reduced price. You pay 72% of the original amount, which is an effective 28% discount.
Does a coupon reduce sales tax?
It depends on the coupon and jurisdiction. Retailer-funded discounts often reduce the taxable selling price, while reimbursed manufacturer coupons can be treated differently. The calculator uses the entered post-discount subtotal as its tax base.
Can a coupon make the subtotal negative?
No. The calculator caps a fixed coupon at the remaining merchandise subtotal. Shipping and tax are never made negative.
Method and sources
The order of product discounts, order discounts, and shipping follows Shopify’s discount combination documentation; Shopify also documents that order discounts are applied before applicable tax. Coupon tax treatment can vary, as shown in the California Department of Tax and Fee Administration coupon guidance. This calculator is a shopping estimate, not tax advice.
