Discount calculator: sale price and percent off

A sale price calculator for the shopping season

This discount calculator answers the questions you ask in front of a price tag: how much will I pay, what is the real percent off, what was the price before the sale, is a "3 for 2" worth it, and which pack size is cheapest per litre. Six calculations sit on one page, results are rounded to the cent and update as you type. The page shows US dollars by default; pick pounds or euros in the "Currency" menu. Nothing is uploaded: everything runs in your browser.

How to use it

1. Choose a calculation at the top: "Sale price", "Percent off", "Original price", "Stacked discounts", "Multibuy deals" or "Unit price".
2. Type your amounts. A point or a comma both work as the decimal mark, so 19.99 and 19,99 give the same result. The "Common discounts" buttons fill in −10%, −20%, −25%, −30%, −40%, −50% or −70% in one click.
3. Read the result and the working underneath. "Copy link to this calculation" makes an address that reopens the page with the same values.

The formulas, with exact examples

Sale price

Sale price = original price × (1 − discount ÷ 100). A $89.90 coat at 40% off: 89.90 × 0.60 = $53.94, a saving of $35.96.

Percent off from two prices

When the tag only shows two prices: (original − sale) ÷ original × 100. From $79.99 down to $59.99: 20 ÷ 79.99 × 100 = 25.003%. The calculator shows 25.0% off and adds the exact value when rounding hides it.

Original price

Divide, don't add. You paid $35 after 30% off: 35 ÷ 0.70 = $50. Adding 30% to $35 would give $45.50, which is wrong.

Stacked discounts don't add up

"30% off, plus an extra 20% at checkout" is not 50% off. The second discount comes off the price that is already lower: $100 becomes $70, then 70 × 0.80 = $56. The total is 44% off. As multipliers: 0.70 × 0.80 = 0.56.

Multibuy deals

"Second item 50% off" on two $20 items costs 20 + 10 = $30 instead of $40: a real discount of 25%, or $15 per item. "3 for 2" on $4.50 items costs $9 instead of $13.50: 33.3% off. "Buy one, get one free" is 50% off. You only save if you buy the whole bundle; a single item stays at full price.

Unit price per kilo, litre or item

The bigger pack is not always the better deal. A 1.5 L bottle at $2.10 works out at $1.40/L, a 2 L bottle at $2.60 at $1.30/L. To compare 400 g for $3.20 with 1 kg for $7.50, the tool converts grams to kilos: $8.00/kg against $7.50/kg. Units are metric (kg, g, L, cl, ml) plus a per-item option.

Reference prices and sale seasons

In the European Union, an advertised price cut must generally be measured against the lowest price the seller charged in the previous 30 days, one of the rules that came with the EU Omnibus Directive. In the UK and the US the rules are different, but consumer law in both countries still expects a "was" price to be a genuine former price. Be wary of comparisons with a list price nobody actually charges.

There is no legally fixed sale period in the US or the UK. In the US, the big moments are Black Friday and Cyber Monday in late November, the post-holiday sales and the long holiday weekends. In the UK, the Boxing Day and January sales are the classic times to buy, along with late November.

FAQ

How do I calculate 30% off $50?

Multiply 50 by 0.70: the sale price is $35.00 and you save $15.00. In the tool, type 50 in "Original price" and click −30%.

Is "second item half price" a good deal?

It is the same as 25% off each item, as long as you buy two. If you only need one, you save nothing. When the two items have different prices, the discount often goes on the cheaper one, so check the terms.

Can I save or share a calculation?

Yes. Your last calculation stays in your browser for your next visit, and "Copy link to this calculation" gives you an address to send or bookmark.

Why are results rounded?

Prices are rounded to the cent, as at the till. Real percentages show one decimal place, with the exact value underneath when it differs.