Discount Calculator
Calculate your real checkout total after a promotional discount and sales tax. Enter the original price, discount percentage, and sales tax rate to see the discount amount, discounted subtotal, tax owed, and final price you'll actually pay.
How It's Calculated
Formula
\text{Discount Amount} = \text{Original Price} \times \text{Discount Rate}
\text{Discounted Subtotal} = \text{Original Price} - \text{Discount Amount}
\text{Sales Tax} = \text{Discounted Subtotal} \times \text{Sales Tax Rate}
\text{Final Price} = \text{Discounted Subtotal} + \text{Sales Tax}This calculator answers a specific checkout question: after a promotional discount and your local sales tax, what will you actually pay? The order of operations matters and is deliberate — the discount is applied first, and sales tax is then calculated on the discounted subtotal, not the original sticker price. That's how real point-of-sale checkout systems work: you're taxed on what you're actually being charged for the item, not on a price you never paid. Applying tax to the original price first would overstate what you owe. This is distinct from a simple 'percent off' calculation — this tool's purpose is the full discount-plus-tax checkout total, not just the discounted price alone.
Worked Examples
Standard case: $80 item, 25% off, 8% sales tax
- Discount amount: $80 × 25% = $20.00
- Discounted subtotal: $80 − $20.00 = $60.00
- Sales tax on the discounted subtotal: $60.00 × 8% = $4.80
- Final price: $60.00 + $4.80 = $64.80
- Discount savings (originalPrice − discountedSubtotal): $80 − $60.00 = $20.00
Fractional discount: $40 item, 12.5% off, 5% sales tax
- Discount amount: $40 × 12.5% = $5.00
- Discounted subtotal: $40 − $5.00 = $35.00
- Sales tax on the discounted subtotal: $35.00 × 5% = $1.75
- Final price: $35.00 + $1.75 = $36.75
Boundary case: $150 item, 100% off (free), 9% sales tax
- Discount amount: $150 × 100% = $150.00
- Discounted subtotal: $150 − $150.00 = $0.00
- Sales tax on a $0.00 subtotal: $0.00 × 9% = $0.00
- Final price: $0.00 + $0.00 = $0.00
- A 100% discount is a valid, well-defined case: the item is free, and there is no tax owed on a $0 purchase price.
Frequently Asked Questions
Why is sales tax applied after the discount, not before?
Because that's how checkout actually works. Retailers charge sales tax on the amount you're being charged for the item — the discounted price — not on the original sticker price you never paid. Calculating tax on the pre-discount price would overstate the tax you owe. This calculator always applies the discount first, then computes tax on the resulting discounted subtotal.
What exactly does "Discount Savings" mean?
Discount Savings is the dollar amount the discount itself saved you: original price minus the discounted subtotal. It is deliberately NOT calculated as original price minus final price — that figure would include the effect of sales tax changing (you owe less tax on a discounted item than you would have on the full price), which has nothing to do with how much the discount saved you. Discount Savings isolates the discount's effect only.
Can I enter a discount over 100%?
No — a discount above 100% isn't meaningful in real commerce, since you can't discount an item by more than its full price. This calculator treats any discount percentage above 100 as invalid input. A 100% discount (a free item) is allowed and handled correctly: it produces a $0 discounted subtotal and $0 tax.
Is this the same as a "percent off" calculator?
Not quite. A simple percent-off calculation only tells you the discounted price itself. This Discount Calculator goes further to answer the real checkout question — what you'll actually pay after both the discount and your local sales tax are applied, in the correct order.
Does this handle stacked or multiple discounts?
No — this calculator models a single promotional discount percentage followed by sales tax. Stacking multiple sequential discounts (e.g. an additional coupon on top of a sale price) would need to be applied one at a time, using the discounted subtotal from one calculation as the original price for the next.