Whether you're shopping in the Black Friday sales, comparing supermarket deals, or trying to work out if that "70% off" claim is genuine, knowing how to calculate discounts helps you make smarter purchasing decisions. This guide explains how to calculate percentage discounts, find sale prices, and determine your actual savings.
Basic Discount Calculations
There are three main discount calculations you might need:
1. Discount amount:
Original Price × (Discount % ÷ 100) = Savings
2. Sale price:
Original Price - Discount Amount = Sale Price
OR: Original Price × (1 - Discount % ÷ 100)
3. Discount percentage:
(Amount Saved ÷ Original Price) × 100 = Discount %
Quick Reference: Common Discounts
| Original | 10% off | 20% off | 25% off | 30% off | 50% off |
|---|---|---|---|---|---|
| £20 | £18 | £16 | £15 | £14 | £10 |
| £30 | £27 | £24 | £22.50 | £21 | £15 |
| £50 | £45 | £40 | £37.50 | £35 | £25 |
| £75 | £67.50 | £60 | £56.25 | £52.50 | £37.50 |
| £100 | £90 | £80 | £75 | £70 | £50 |
| £150 | £135 | £120 | £112.50 | £105 | £75 |
| £200 | £180 | £160 | £150 | £140 | £100 |
Try Our Free Percentage Calculator
Get instant results with our Percentage Calculator. Also check our VAT Calculator and Salary Calculator.
Mental Maths Shortcuts
Calculate discounts quickly in your head with these tricks:
10% Off
Simply move the decimal point one place left: £85 → £8.50 discount → pay £76.50
20% Off
Calculate 10% and double it: £60 → £6 × 2 = £12 discount → pay £48
25% Off (Quarter Off)
Divide by 4: £80 ÷ 4 = £20 discount → pay £60
50% Off (Half Price)
Simply halve the price: £45 ÷ 2 = £22.50
33% Off (Third Off)
Divide by 3: £90 ÷ 3 = £30 discount → pay £60
Stacking Discounts
When multiple discounts apply (e.g., sale + voucher code), they multiply rather than add:
£100 item with 20% off then 10% off:
£100 × 0.80 = £80 (after 20% off)
£80 × 0.90 = £72 (after additional 10% off)
Actual total discount: 28%, not 30%
Comparing Discount Types
| Discount Type | How It Works | Example |
|---|---|---|
| Percentage off | Fixed % of price | 30% off = £30 saved on £100 |
| Fixed amount off | Set £ amount | £20 off (regardless of price) |
| Buy one get one free | 50% off when buying 2 | 2 × £15 items = £15 (50% off) |
| 3 for 2 | 33% off when buying 3 | 3 × £10 items = £20 (33% off) |
| Multi-buy | Discount at quantity | £2 each or 5 for £8 |
UK Sales Calendar 2025
Know when to find the best deals:
- January Sales: 26 Dec onwards - post-Christmas clearance
- Easter Sales: March/April - spring fashion
- May Bank Holiday: DIY and garden deals
- Amazon Prime Day: July - electronics and more
- Back to School: August/September - clothing and stationery
- Black Friday: Last Friday of November - biggest discounts
- Cyber Monday: Monday after Black Friday - online deals
- Boxing Day: 26 December - traditional sales start
When Discounts Aren't Bargains
Watch out for these retail tricks:
- Inflated original prices: RRP set unrealistically high
- Shrinkflation: Same price, smaller product
- Anchor pricing: High "was" price to make discount look better
- Limited stock: Pressure tactics with "only 2 left"
- Multi-buy manipulation: Individual price raised to make offer seem better
Calculate Your Discount
Use our free discount calculator for instant results
Use Discount CalculatorHow VAT Affects Discounts in the UK
Value Added Tax (VAT) in the UK is currently set at 20% for most goods and services, with reduced rates of 5% for certain items such as children's car seats and home energy, and 0% for essentials like most food and children's clothing. Understanding how VAT interacts with discounts is important for both consumers and businesses.
When a retailer advertises a percentage discount, it is almost always applied to the VAT-inclusive price. For example, a product priced at £120 (including £20 VAT on the £100 base price) with a 25% discount would be reduced to £90. The VAT within that £90 is £15 (calculated as £90 divided by 6), meaning the pre-VAT discounted price is £75. The retailer pays VAT to HMRC based on the actual selling price, not the original price.
For business-to-business transactions where prices are often quoted excluding VAT, the discount is applied to the net price before VAT is added. This distinction is critical when comparing quotes from different suppliers, as a 10% discount on a VAT-exclusive price of £1,000 saves you £100 plus the VAT on that £100 (£20), totalling £120 in actual savings.
UK Sale Seasons and When to Find the Best Deals
UK retail follows a predictable calendar of major sale periods, and knowing when these occur can help you time your purchases for maximum savings.
Boxing Day and January sales: Traditionally the biggest sale period, running from 26 December through much of January. Discounts typically range from 30% to 70% off, with the deepest reductions on fashion, electronics, and homewares. Many retailers now begin their sales on Christmas Eve or even earlier.
Black Friday and Cyber Monday: Imported from the United States and now firmly established in the UK, Black Friday falls on the last Friday in November. In 2025, Black Friday is on 28 November. Discounts are often strongest on technology, appliances, and gaming products, though an increasing number of UK retailers participate across all categories.
Easter sales: A smaller but growing sale period, particularly for fashion retailers transitioning from winter to spring collections. Discounts of 20-40% are common.
Summer sales: Running from late June through July, summer sales coincide with end-of-season clearance. Fashion retailers often offer the deepest discounts during this period as they make room for autumn stock.
Amazon Prime Day: Usually held in July, this event offers exclusive discounts to Amazon Prime members. While not a traditional UK sale, it has become one of the largest online shopping events in Britain.
Your Consumer Rights on Discounted Goods
Under the Consumer Rights Act 2015, your statutory rights are exactly the same whether you buy goods at full price or in a sale. This is a commonly misunderstood area of UK consumer law, and some retailers incorrectly claim that sale items cannot be returned or refunded.
Faulty goods: If a discounted item is faulty (not of satisfactory quality, not fit for purpose, or not as described), you are entitled to a full refund within 30 days of purchase. Between 30 days and 6 months, the retailer must be given one opportunity to repair or replace the item before you can claim a refund. These rights apply regardless of whether the item was discounted.
Change of mind: For in-store purchases, retailers are not legally obligated to accept returns if you simply change your mind, though many stores offer this as a goodwill policy. For online purchases, the Consumer Contracts Regulations 2013 give you a 14-day cooling-off period from the date you receive the goods, during which you can return items for any reason. This applies equally to discounted items bought online.
Misleading pricing: UK law prohibits misleading pricing practices. Under the Consumer Protection from Unfair Trading Regulations 2008, a retailer must have offered an item at the higher "was" price for a reasonable period before advertising a discount. The Chartered Trading Standards Institute recommends that the original price should have been the prevailing price for at least 28 consecutive days in the previous 6 months.
Frequently Asked Questions
How do I calculate the original price from a sale price?
To find the original price when you know the sale price and discount percentage, divide the sale price by (1 minus the discount expressed as a decimal). For example, if an item costs £60 after a 25% discount, the original price is £60 divided by 0.75, which equals £80. Our calculator can perform this reverse calculation instantly, saving you the mental arithmetic.
Is a bigger percentage discount always a better deal?
Not necessarily. A common retail technique is to inflate the original price before applying a large discount, making the deal appear more attractive than it is. Always compare the final selling price against what other retailers charge for the same item. Price comparison sites such as PriceRunner, Google Shopping, and idealo can help you verify whether a discounted price genuinely represents good value in the current UK market.
How do stacked discounts work?
Stacked discounts occur when multiple percentage reductions are applied sequentially. For instance, a 20% sale discount followed by an additional 10% loyalty card discount does not equal 30% off. Instead, the 20% is applied first, then the 10% is taken from the already-reduced price. On a £100 item, the first discount brings it to £80, and the second brings it to £72, for a combined saving of 28% rather than 30%. The order in which discounts are applied does not affect the final price when both are percentages.
Do UK retailers have to honour pricing errors?
No. Under English contract law, a displayed price is an "invitation to treat" rather than a binding offer. If a retailer makes a genuine pricing error (for example, listing a £500 television at £5), they are not legally obliged to sell at that price. Most retailers include terms and conditions stating they may cancel orders placed at incorrect prices. However, once a transaction is completed in-store and you have paid and received the goods, the contract is generally considered complete.
Understanding UK Consumer Discount Regulations
The UK has some of the strongest consumer protection laws in Europe when it comes to pricing and discounts. The Competition and Markets Authority (CMA) and Trading Standards actively monitor retailers to ensure discount claims are genuine and not misleading to consumers.
Under the Consumer Protection from Unfair Trading Regulations 2008, it is illegal for retailers to use misleading pricing practices. A common area of enforcement involves "was/now" pricing, where a product is shown with a higher original price crossed out alongside the discounted price. The Chartered Trading Standards Institute guidance states that the higher "was" price should have been the prevailing selling price for at least 28 consecutive days in the previous six months. Retailers found to breach these regulations can face enforcement action, fines, and reputational damage.
The UK retail sector generates over 400 billion pounds in annual sales, with Black Friday alone accounting for estimated spending of 13 billion pounds across in-store and online channels. Research by consumer group Which? has repeatedly found that a significant proportion of Black Friday deals are available at the same price or cheaper at other times of the year. Their analysis has shown that up to 85 percent of products tracked were cheaper or the same price in the six months before Black Friday, highlighting the importance of price comparison before assuming a sale discount is genuine.
For online purchases, UK consumers benefit from the Consumer Contracts Regulations 2013, which provide a 14-day cooling-off period from the date of delivery. This applies to both full-price and discounted items, giving shoppers the right to return products for a full refund regardless of whether they were bought in a sale. This right does not apply to in-store purchases unless the retailer offers their own returns policy.
Smart Discount Shopping Tips for UK Consumers
- Track prices before sales events: Use free browser extensions like Keepa or CamelCamelCamel for Amazon purchases, and PriceRunner or Google Shopping for general retail, to verify that the advertised discount represents a genuine reduction from the normal selling price.
- Stack cashback with discounts: UK cashback sites such as TopCashback and Quidco offer additional savings on top of sale prices. Combine these with store loyalty cards and credit card rewards to maximise your total savings on discounted purchases.
- Check unit prices in supermarkets: UK supermarkets are required by law to display unit prices (price per kilogram, litre, or individual item) on shelf labels. Multi-buy offers are not always cheaper per unit than buying singles, so always compare the unit price before assuming a deal is worthwhile.
- Know your return rights: Under the Consumer Rights Act 2015, your statutory rights on faulty goods are identical whether you paid full price or a sale price. Do not accept a store refusing to refund a faulty sale item.
Common Discount Questions
Are UK retailers legally required to display the original price when offering a discount?
How does VAT work with discounted prices in the UK?
What is the best time of year to find discounts in the UK?
James Mitchell, ACCA
Chartered Accountant & Former HMRC Advisor
James is a Chartered Certified Accountant (ACCA) specialising in UK personal taxation and financial planning. With over 12 years in practice and a background as a former HMRC compliance officer, he brings authoritative insight to complex tax topics.