Percent Off Calculator

How percent off works

Quick answer: multiply the original price by the percent off divided by 100 to get the amount saved, then subtract it from the original price. 20% off $80 saves $16 and leaves a sale price of $64.

How to calculate percent off

1. 1Divide the percent off by 100 to turn it into a decimal (20% becomes 0.20).
2. 2Multiply by the original price to get the amount saved.
3. 3Subtract the amount saved from the original price to get the sale price.

Quick mental maths for common discounts

For 10% off, move the decimal point one place left to get the saving, then subtract it. For 20% off, double that tenth. For 15%, add half of the tenth to the tenth. For 25% off, take a quarter of the price, and for 50% off, halve it. On $80 a tenth is $8, so 20% off saves $16 and 15% off saves $12. Use mental maths for a quick check in the shop, and the percentage off calculator whenever a second discount or tax is involved.

Stacking two discounts

A second discount applies to the already reduced price, not the original, so the two percentages never simply add. Multiply the two remaining shares: 20% off then 10% off leaves 0.80 × 0.90 = 0.72 of the price, which is 28% off in total. On the $249.99 jacket, 15% off then 10% off leaves 0.85 × 0.90 = 0.765 of the price, so $191.24 and 23.5% off, not 25%.

Percent off with sales tax

In many US checkouts the discount comes first and tax is charged on the sale price. Multiply the sale price by the tax rate to get the tax, then add it. Both steps are multiplications, so taking tax first gives the same total. Some places and coupon types charge tax on the pre-discount price instead, which costs more, so check how your store does it.

How to find the discount from two prices

To calculate the percentage discount, divide the amount saved by the original price, not the sale price, and multiply by 100. The percentage discount formula is (original − sale) ÷ original × 100. A $60 item on sale for $45 is 25% off. Use the two-price mode of the percentage discount calculator above to run it.

How to find the original price

If you only know the sale price and the percent off, divide the sale price by (1 − percent off ÷ 100). A sale price of $64 after 20% off came from 64 ÷ 0.80 = $80. The reverse percentage calculator does this in one step.

Percent off examples

Common percentages off an $80 item:

Percent off code

Both versions reproduce the examples above ($64.00, $212.49, $72.00 and $97.20 with tax) and reject a percent outside 0 to 100.

JavaScript

1const round2 = (x) => Math.round((x + Number.EPSILON) * 100) / 100;2​3function check(name, v, max = Infinity) {4  if (typeof v !== "number" || !Number.isFinite(v)) throw new TypeError(`${name} must be a finite number`);5  if (v < 0 || v > max) throw new RangeError(`${name} must be between 0 and ${max}`);6}7​8export function percentOff(price, percentOff, { secondPercentOff = 0, taxPercent = 0 } = {}) {9  check("price", price);10  check("percentOff", percentOff, 100);11  check("secondPercentOff", secondPercentOff, 100);12  check("taxPercent", taxPercent, 100);13  const salePrice = price * (1 - percentOff / 100) * (1 - secondPercentOff / 100);14  const tax = salePrice * (taxPercent / 100);15  return {16    salePrice: round2(salePrice),17    saved: round2(price - salePrice),18    tax: round2(tax),19    total: round2(salePrice + tax),20  };21}22​23export function discountFromPrices(original, sale) {24  check("original", original);25  check("sale", sale);26  if (original === 0) throw new RangeError("original must be greater than 0");27  if (sale > original) throw new RangeError("sale must not exceed original");28  return ((original - sale) / original) * 100;29}

Python

1from decimal import Decimal, ROUND_HALF_UP2import math3​4CENT = Decimal("0.01")5​6def _num(name, v, hi=None):7    if isinstance(v, bool) or not isinstance(v, (int, float, Decimal)) or not math.isfinite(float(v)):8        raise ValueError(f"{name} must be a finite number")9    v = Decimal(str(v))10    if v < 0 or (hi is not None and v > hi):11        raise ValueError(f"{name} is out of range")12    return v13​14def percent_off(price, percent_off, second_percent_off=0, tax_percent=0):15    price = _num("price", price)16    p1 = _num("percent_off", percent_off, 100)17    p2 = _num("second_percent_off", second_percent_off, 100)18    tax_p = _num("tax_percent", tax_percent, 100)19    sale = price * (1 - p1 / 100) * (1 - p2 / 100)20    tax = sale * tax_p / 10021    q = lambda x: x.quantize(CENT, rounding=ROUND_HALF_UP)22    return {"sale_price": q(sale), "saved": q(price - sale), "tax": q(tax), "total": q(sale + tax)}

Use Decimal (Python) or integer cents for money. Binary floats can land a half-cent on the wrong side.

Privacy and input safety

Prices are calculated in your browser. The numbers you enter are not sent to a server or stored.

• A percent off below 0 or above 100 is refused, because a negative discount is a price increase and more than 100% off would give a negative price.
• A comma followed by exactly three digits is read as a thousands separator, so 1,200 is 1200. Any other comma is a decimal point, so 12,50 is 12.50, and a number starting with 0, such as 0,500, is read as a decimal. Mixed formats such as 1.234,5 and ambiguous entries such as 1,2,3 are refused instead of guessed. Spaces, including no-break spaces, between digit groups are ignored.

Common percent off mistakes

Percent off vs discount vs markdown vs markup

Percent off and markdown describe the same reduction. The percentage decrease calculator and percentage increase calculator cover those two rows for any value, not only prices. Markup uses the seller's cost as its base, so a 50% markup is not the same as a 50% margin or a 50% discount.