Discount calculator · percentage off
Discount calculator – work out the sale price and saving
Enter the price and the discount percentage to see the final price and the saving in pounds. The calculator works the other way round too: it gives you the discount percentage from two prices, or digs out the original price.
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Three situations where you need a discount calculator
A sale sign rarely tells you what you actually want to know. In practice there are three questions, and they point in different directions.
"How much does this cost at the till?"
The most common situation. The price is £79.90 and the sign says −40%. The discount in pounds is
79.90 × 0.40 = £31.96 and you pay £47.94. Rule of thumb: when the discount is 40%,
you pay 60% of the price, i.e. you multiply the price by 0.6.
"Is this really a good deal?"
You see two prices – the old one crossed out and the new one. The discount percentage comes from the formula
(normal price − sale price) / normal price × 100. So a price of £129 → £89 is a
31.01% discount. This is useful because shops sometimes quote the discount percentage
rounded up.
"What was the normal price?"
An online shop shows only £59.40 and a "−25%" tag. The original price is worked out by division, not by
adding 25% back on: 59.40 / 0.75 = £79.20. This is the most common mistake in discount sums.
If you added 25% to the sale price, you'd get £74.25 – the wrong answer.
Discount table: how much you pay and how much you save
The discount percentage tells you directly what share of the price you pay. The table is handy to remember when opening the calculator isn't an option.
| Discount | You pay of the price | Multiplier | £100 costs | Saving |
|---|---|---|---|---|
| 10% | 90% | × 0.90 | £90.00 | £10.00 |
| 15% | 85% | × 0.85 | £85.00 | £15.00 |
| 20% | 80% | × 0.80 | £80.00 | £20.00 |
| 25% | 75% | × 0.75 | £75.00 | £25.00 |
| 30% | 70% | × 0.70 | £70.00 | £30.00 |
| 40% | 60% | × 0.60 | £60.00 | £40.00 |
| 50% | 50% | × 0.50 | £50.00 | £50.00 |
| 70% | 30% | × 0.30 | £30.00 | £70.00 |
Successive discounts don't add up
The sign says "−30% and a further −20% at the till". That is not a 50% discount. The second discount is taken from the already-reduced price, so the real overall discount is 44%.
The sum goes like this: £200 × 0.70 = £140, and from that £140 × 0.80 = £112. The saving comes to £88, which is 44% of the original. The difference from the 50% assumption is £12 on a single item – with a basketful the gap grows quickly. The calculator's Successive discounts tab works out up to three consecutive discounts and shows the intermediate steps.
The same applies the other way: two 10% increases are not 20% but 21%. More on this on the percentage change calculator page.
Discounts and VAT
Consumer prices in the UK include VAT, so the discount is calculated from the VAT-inclusive price. A discount also reduces the VAT amount: at 20% VAT, £100 contains £16.67 of VAT, but after a 30% discount £70 contains only £11.67 of VAT.
The pitfalls of a reverse VAT calculation are covered in the guide how to work out VAT and the net price backwards. As a business you invoice the customer the discounted price and account for the VAT on that. If you need a breakdown of the net price, the VAT amount and the gross price, use the VAT calculator. You can see the effect on margin with the margin calculator: a 30% discount off the sale price eats into the margin considerably more than 30% of the margin.
Shopping checklist
- Compare the unit price, not just the discount percentage. 3 items at −25% can be dearer than a competitor's normal price.
- Check the reference price. The discount is calculated from a previous price that may only have been in force for a short time.
- Include delivery costs. A 20% discount on a £39 item is £7.80, which quickly disappears into £5.90 of postage.
- Remember the right to return. It doesn't show in the price, but it's part of the value of the deal.
The basics of discount calculation
A discount is always calculated from the normal price, and successive discounts are multiplied. Below are the formulas, the concepts and the limits of the calculator.
Formulas and examples
Discounted price
price × (1 − discount / 100)Example
£79.90 −40%: 79.90 × 0.60 = £47.94.
Note
The multiplier 0.60 tells you directly what share of the price you pay.
Discount percentage from two prices
(old − new) / old × 100Example
£129 → £89: 40 / 129 × 100 = 31.01%.
Note
Shops often round the discount percentage up in their marketing.
Original price backwards
sale price / (1 − discount / 100)Example
£59.40 was −25%: 59.40 / 0.75 = £79.20.
Note
Don't add the same percentage to the sale price – the result is too small.
Successive discounts
price × (1−a₁) × (1−a₂) × (1−a₃)Example
£200 −30% and −20%: 200 × 0.7 × 0.8 = £112, i.e. −44%.
Note
Percentages aren't added together. The difference from the 50% assumption is £12 in this example.
Concepts and classification
| Discount percentage | The discount as a share of the normal price. |
|---|---|
| Saving | The discount as an amount of money. |
| Reference price | The price the discount is measured against. |
| Successive discount | From the second discount onwards, calculated from the already-reduced price. |
| Unit price | The price per item, kilo or litre – the best figure for comparison. |
Limitations of the calculator
- The calculator does not check whether the stated normal price was really in force.
- Delivery costs, the right to return and loyalty benefits are not taken into account.
- With a discount of 100% or more the original price cannot be worked out.
- Consumer prices include VAT; use the VAT calculator for a breakdown.
How up to date the information is
When it was checked
Content and the percentages used were checked on 12 August 2026.
Disclaimer
The calculator gives a mathematical result from the numbers you enter. It is not an official decision, an offer or professional advice. See the terms of use.
Topics
This calculator belongs to the following topic areas. On the topic page you'll find all the calculators and guides on the same theme in one place.
Calculators related to discounts
Frequently asked questions about the discount calculator
How do I take 40 percent off a price?
Multiply the price by 0.6. For example 79.90 × 0.6 = £47.94. Another way is to work out the discount first (79.90 × 0.4 = £31.96) and subtract it from the price. Same result – pick whichever is easier to remember.
How do I work out the discount percentage from two prices?
(old price − new price) / old price × 100. For example from £129 to £89: (129 − 89) / 129 × 100 = 31.01%. The important thing is to divide by the old price, because that is the 100% the discount is calculated from.
How do I find the original price when I only know the sale price?
Divide the sale price by (1 − discount). If £59.40 has 25% off, the original price is 59.40 / 0.75 = £79.20. Don't add 25% to the sale price – that gives too small a result, because the percentage would be taken from the wrong number.
Are two successive discounts the same as their sum?
No. −30% then −20% is 44% in total, not 50%. The second discount is calculated from the already-reduced price. The formula is price × 0.7 × 0.8. The calculator's fourth tab does this for you and shows the intermediate steps.
Does the sale price include VAT?
Consumer prices in the UK include VAT, so the discount is calculated from the VAT-inclusive price and the VAT amount falls too. You can get a breakdown with the VAT calculator.
Can I work out how much I save on a whole basket?
Yes. Enter the basket total as the original price and the discount percentage – the result shows the saving in pounds. If the items have different discounts, work them out separately and add the savings together.