How to Calculate Discounts, Coupons and Final Prices

A stacked discount is rarely the sum of its parts. "30% off plus an extra 20% with this code" is not 50% off, and the gap is usually where the offer earns its margin.

What the Discount Calculator does

Works out what you actually pay after a discount, an optional stacked coupon and sales tax.

The order matters and is fixed for a reason: the coupon applies to the already-reduced price, and tax applies last, to what you actually pay. That is how nearly every till in the world does it.

Open the Discount Calculator and follow the settings and checks below.

How stacking really works

Setting	What it means
Order applied	Discount → coupon on the reduced price → tax on the total
30% then 20%	44% off, not 50%
50% then 50%	75% off, not free
Discount range	0–100%
Coupon range	0–100%, optional
Sales tax	Optional, applied at the end
Currencies	USD, EUR, GBP, CAD, AUD, INR

How to use it

1. Enter the original price and the main discount.
2. Add a coupon percentage if one stacks on top.
3. Add sales tax if your region adds it at the till.
4. Compare the final figure against the headline claim.

Practical advice

Two stacked percentages multiply rather than add. Thirty percent then twenty percent leaves you paying 0.7 × 0.8 = 56% of the original, so 44% off rather than the 50% it sounds like. The difference is small on a jumper and substantial on a sofa.

Common questions

Why is 30% plus 20% not 50%?

Because the second discount applies to the already-reduced price, not the original. You pay 70% of the price, then 80% of that — 56% overall, so 44% off. Stacked percentages multiply; they never add.

Should tax go before or after the discount?

After, in almost every system. You are taxed on what you actually pay, so the discount comes off first. This tool follows that order.

Does the order of two discounts matter?

Not to the final price — multiplication is commutative, so 30% then 20% costs the same as 20% then 30%. It can matter to whether a retailer allows the combination at all.

How do I work out the original price from a sale price?

Divide rather than adding the percentage back. Something 25% off at 60 was 60 ÷ 0.75 = 80. Adding 25% to 60 gives 75, which is the classic error.

Useful next tools

• Percentage Calculator — Percent of, is-what-percent, and percentage change.
• VAT / GST Calculator — Add or remove sales tax from any price.
• Tip & Bill Split — Split a bill with tip across any number of people.
• Profit Margin — Margin, markup and selling price from cost.
• Break-Even Point — Units and revenue needed to cover fixed costs.
• Currency Converter — Live exchange rates from European Central Bank data.

Vootkit provides a browser calculator and educational guidance. Results depend on the values and units you enter, so verify important financial, academic, safety or professional decisions with an appropriate authoritative source.