How to Calculate a Percentage Discount

Calculate the discount amount

Convert the percentage to a decimal by dividing it by 100, then multiply by the original price:

Saving = original price × discount percentage ÷ 100

For 20% off £80, the calculation is £80 × 0.20 = £16. That £16 is the saving, not the amount to pay.

Keep money calculations to sufficient precision until the final answer, then display the result in pounds and pence. When a retailer applies its own item-level rounding, the checkout total may differ by a penny from a basket-wide estimate.

Subtract the saving from the original price

Once the saving is known, subtract it:

Sale price = original price − saving

In the £80 example, £80 − £16 = £64. You can also calculate the final price directly using the percentage that remains. A 20% discount leaves 80%, so £80 × 0.80 = £64.

The direct multiplier is:

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

For 35% off, 65% remains, so multiply by 0.65. This method is useful when checking many prices with the same reduction.

Use simple mental-percentage shortcuts

Ten per cent is the original amount divided by ten. Five per cent is half of 10%, and 1% is divided by 100. Combine these pieces:

• 15%: 10% + 5%.
• 25%: one quarter of the price.
• 30%: three lots of 10%.
• 50%: half of the price.
• 75%: three quarters saved, so one quarter remains.

For £60 at 25% off, one quarter is £15, leaving £45. For irregular percentages or several items, a calculator reduces avoidable arithmetic errors.

Apply multiple discounts in order

Successive discounts apply to different bases, so they are not normally added. With 20% off followed by 10% off, a £100 item first becomes £80. The second reduction is £8, producing £72.

The combined saving is £28, or 28% of the original—not 30%. Multiply the remaining proportions to check: 0.80 × 0.90 = 0.72, meaning 72% remains.

A fixed voucher adds another step. If £10 is taken after the two discounts, the final price becomes £62. Read the promotion terms because an offer may apply before or after another reduction, require a minimum spend or exclude particular items.

Find the original price before the discount

If the sale price and discount percentage are known, divide by the remaining proportion:

Original price = sale price ÷ (1 − discount ÷ 100)

A coat costs £72 after 20% off. Since 80% remains, £72 ÷ 0.80 = £90 original price. Do not add 20% to £72: 20% of the reduced price uses a smaller base and gives £86.40.

A reverse result assumes the displayed percentage was applied directly to the original price. Additional vouchers, rounding or bundle rules can prevent an exact reconstruction.

Compare sale offers using final prices

Convert every offer to the amount actually payable. Compare “30% off £50” with “£12 off £50”: the percentage saves £15 and costs £35, while the voucher costs £38. Then include delivery fees, membership costs and quantity requirements.

For different pack sizes, calculate the final unit price as well. A larger discounted pack is not automatically better value if much of it will be unused.

Calculate basket discounts and unit prices

A basket-wide percentage may apply to the subtotal rather than each displayed item. Add the eligible prices first, apply the discount and then include any delivery or charges that the offer excludes. If only selected items qualify, separate them before calculating.

Example: three eligible items cost £18, £27 and £35. Their subtotal is £80. A 15% basket discount saves £12 and leaves £68 before delivery. If a £5 delivery charge is not discounted, the payable total becomes £73.

For multipacks, divide the final price by the number of usable units. A 12-pack reduced from £30 to £24 costs £2 per unit. An 8-pack at £17.60 costs £2.20 per unit, so the larger pack is cheaper per item even though its total price is higher.

Also check returns and refund terms. A refund may be based on the discounted amount allocated to an item rather than its original shelf price. Loyalty points, cashback and delayed rebates should be recorded separately because they may not reduce the amount paid at checkout.

Common discount mistakes

• Reporting the saving as the sale price.
• Adding successive percentage discounts together.
• Adding the discount percentage to a sale price to recover the original.
• Ignoring delivery, minimum spend or excluded items.
• Comparing percentages without checking the original prices.
• Rounding too early across several items.

For the broader method behind these examples, read how to calculate percentages and percentage increase and decrease.

Percentage discount worked examples

A 25% discount on £80 saves £20 and gives a £60 sale price. A 30% discount on £50 saves £15 and gives a £35 sale price. Calculate the saving first, then subtract it from the original price.

Use the UsefulFox Percentage Calculator to work out percentages quickly.

Frequently asked questions