Percent Off Calculator

What this calculator tells you

A percent off calculator shows how much a price has fallen as a percentage of its original value. Where the discount calculator starts from a percentage and finds the sale price, this one starts from two prices and finds the percentage reduction between them. It is useful for checking a sale claim or measuring any fall in value, such as a price cut by a supplier.

The answer is the drop in price divided by the original price, expressed as a percentage. Because the calculation starts from the original price, the same cash drop can be a very different percentage depending on the price it started from.

How the percentage is worked out

Subtract the new price from the original price to get the amount of the drop. Divide that amount by the original price, and multiply by 100 to express it as a percentage. The formula is the original price minus the new price, divided by the original price, then multiplied by 100.

A worked example

Suppose a jacket was 80 and is now 60. The drop is 20. Dividing 20 by the original 80 gives 0.25, which is 25% off. Checking the other way, 25% of 80 is 20, so the sale price of 60 is confirmed. Had the jacket started at 60 and fallen to 40, the drop would be 20 again, but the percentage would be 33.3%, because the base is smaller.

Why the base price matters

A discount is always measured against the price before the reduction. Retailers sometimes show a large percentage based on an inflated or short-lived 'original' price, so the advertised saving may not reflect what the item was previously sold for. Compare the sale price with the lowest price the item has recently sold at, to judge the real value of the offer.

Limits of the calculation

The calculator compares two prices and does not check whether the original price was genuine. It also ignores taxes, delivery fees, and any conditions attached to the offer, such as a minimum spend or a requirement to join a scheme. A percentage off the headline price can differ from the percentage off the final amount you pay.

Checking retailer claims

A retailer may show a higher original price than the item has recently sold for. Check price history where available, and compare the sale price with other retailers. A large percentage off a price that was never charged is not a real saving, so the reference price matters as much as the percentage.

Using the result

Use the calculator to compare the real reduction across different offers, to measure how much a cost has changed over time, and to decide whether a price drop is large enough to act on. Combine it with the final amount after all charges to see the true saving.

Working out the original price

If you know the sale price and the percentage off, and want the original price, divide the sale price by one minus the percentage as a decimal. A price of 60 after 25% off was 80 before the discount. This is useful for checking whether a reduction was applied correctly to a bill or invoice, and for seeing how much a product's price has changed over time.

The reverse calculation is also useful when comparing prices across shops, because it shows which shop's reference price is genuine and which is inflated for effect.