Discount Calculator

How to use the discount calculator

Start on the Sale price tab. Type the original price and, if you are buying more than one, the quantity. Then either paste the deal exactly as the shop words it, for example “30% off + extra 20% at checkout” or “Buy 2 get 1 free”, and press Read deal, or build the discounts yourself. Each discount can be a percentage, a fixed amount, a multi-buy such as “3 for $10”, a buy-X-get-Y offer, or a spend-and-save coupon like “$20 off $100+”.

Discounts are applied from top to bottom, just like a till. Use the arrows to change the order. The result shows what you pay, how much you save, and a line-by-line breakdown. Pick where you are shopping to add US sales tax or to see the VAT already inside a UK or EU price. The other tabs work out the percent off between two prices, the original price before a discount, and which of up to four deals is the best value.

Every input is saved in the page address, so Copy link lets you send the exact calculation to someone else.

How to calculate a discount

The formula is simple:

Sale price = original price × (1 − discount ÷ 100)

For 25% off $80, that is 80 × 0.75 = $60, and the saving is $20. To go the other way and find the percent off between a “was” and a “now” price, divide the difference by the original: ($129.99 − $89.99) ÷ $129.99 = 30.77% off.

Shops round to the nearest cent or penny at each step, so this calculator does the same. That is why $79.99 with 30% off and then an extra 20% off comes to $44.79 rather than an amount with fractions of a cent.

“Extra % off”: why 30% + 20% is not 50% off

Banners such as “an extra 20% off sale prices” are designed to sound bigger than they are. The extra discount is taken from the price that has already been cut, not from the original price. On a $100 item:

1. 30% off $100 = $70.
2. An extra 20% off $70 = $56.

You save $44, which is 44% off, not 50%. The more discounts you stack, the bigger the gap between the numbers added together and the real total. The calculator shows the single percentage your whole stack is worth.

Does the order of coupons matter?

With only percentage discounts, the order makes no difference: 30% then 20% gives the same price as 20% then 30%. Once a fixed-amount coupon joins in, it does matter. On a $100 basket:

• 20% off, then $10 off: $80 − $10 = $70.
• $10 off, then 20% off: $90 × 0.8 = $72.

The shop's checkout decides the order, not you. When your discounts can give different totals, the calculator warns you and shows the cheapest and dearest outcome, so you know what to expect before you pay.

Sales tax, VAT and discounts

In the US, sales tax is added at the till and the rate depends on your state, county and city. A store discount usually lowers the amount that tax is charged on. Manufacturer coupons are often different: because the manufacturer pays the shop back, many states charge tax on the price before the coupon. Tick the manufacturer-coupon box to see that effect, and treat it as a guide, because the rules vary by state. The state list fills in the state rate only; your receipt shows your full local rate.

In the UK and the EU, prices shown to shoppers already include VAT, so a discount comes off a VAT-inclusive price and nothing is added at the till. Choose the UK or your EU country and the calculator shows how much of your final price is VAT, using the standard rate. Some goods, such as many foods and children's clothes in the UK, have a reduced or zero rate, so you can change the rate if you need to.

BOGO, 3-for-2 and multi-buy deals in percent

Multi-buys are easier to judge once you turn them into a percentage of what you pay in total:

These savings only count if you wanted all the items. If you only needed one, a straight 20% off is the better deal. With odd quantities, only full sets get the discount: “3 for 2” on four items means one free item and three at full price. When items in a multi-buy have different prices, shops usually make the cheapest one free; this calculator assumes the items cost the same.

Price per unit: compare pack sizes

A bigger pack is not always cheaper per ounce or per 100 grams, especially once a sale is applied to the smaller one. On the Compare deals tab, enter each option's price, deal, shipping, quantity and the size of each item. The calculator converts ounces, pounds, grams, kilograms, millilitres, litres and US fluid ounces to the same unit and marks the cheapest. If the sizes can't be compared, for example grams against millilitres, it compares the price per item instead.

Is it a real deal? “Was” prices, the EU 30-day rule and what Which? found

A discount is only as honest as the “was” price it is measured from. In a study published in November 2025, the UK consumer group Which? tracked 175 products at eight retailers for a year around Black Friday 2024. It found that 83% were the same price or cheaper at least once outside the sales period, and none of the deals was at its lowest price of the year in the sale.

Rules on reference prices differ by region. In the EU, a shop announcing a price reduction must show its prior price, which is the lowest price it charged in at least the 30 days before the reduction (Article 6a of the Price Indication Directive, as amended in 2019). In the US, the Federal Trade Commission's Guides Against Deceptive Pricing say a former price should be one the item was genuinely offered at for a reasonably substantial period. UK guidance for traders says “was” prices must be genuine and must not mislead.

The simplest protection is your own record. Note or screenshot the price of things you want a few weeks before a big sale, then enter the lowest price you saw in the Is it a real deal? box. The calculator shows your real saving against that price, or how much more you would be paying.

Black Friday and Cyber Monday checklist

• Check the price history rather than the “was” price, and compare at least two shops.
• Add shipping and tax before comparing. A lower price with paid delivery can cost more in the end.
• Read the returns policy. Some sale items have shorter return windows or can't be returned.
• Check who is selling. On marketplaces, the seller may not be the platform itself.
• Pay in a way that protects you. Credit cards usually offer the strongest dispute rights. In the UK, Section 75 of the Consumer Credit Act covers credit card purchases over £100 and up to £30,000.
• Be wary of deal links in emails and texts. Type the shop's address yourself, or check the web address carefully before you enter card details.

Prices in this calculator are estimates. Always check the final price at checkout.

Last updated: 2026-11-14