How to Calculate Price Per Unit and Find the Best Value

Price per unit = Total price / Quantity Units must match for the comparison to be valid: - Both in pence per gram (or per 100g) - Both in pence per ml (or per litre) - Both in pence per item Example: washing powder 500g for £3.99: £3.99/500 = 0.798p/g = 79.8p per 100g 1kg for £6.49: £6.49/1000 = 0.649p/g = 64.9p per 100g 3kg for £14.99: £14.99/3000 = 0.500p/g = 50.0p per 100g Largest pack wins here — 37% cheaper per gram vs smallest.

Despite common perception, bulk packs aren't always best value. Supermarket own-brand cereal: 500g box: £1.25 → 25p per 100g 1kg box: £2.75 → 27.5p per 100g (MORE expensive!) Tinned tomatoes: 400g tin: 59p → 14.75p per 100g 2 x 400g multipack: £1.39 → 17.4p per 100g 800g tin: £1.05 → 13.1p per 100g The 800g tin beats the multipack despite looking similar. You cannot assume — always check the shelf label.

UK law (Units of Measurement Regulations) requires supermarkets to display price per unit (per litre, per kg, per item etc.) for most packaged goods. However: - Comparison units aren't standardised across categories (per 100g vs per kg vs per portion) - Promotional displays may omit unit prices - Website unit prices are often in different units between similar products Consistent approach: always convert to the same base unit For food: pence per 100g (multiply per gram rate by 100) For drinks: pence per litre (or per 100ml)

Many supermarkets now use "member prices" vs "regular prices." Regular price: £4.00 for 500g → 80p per 100g Member price: £2.50 for 500g → 50p per 100g Compare member price vs competitor's non-member price: Competitor 600g: £2.80 → 46.7p per 100g Competitor still cheaper even without loyalty card. Always compare: Member price vs competitor regular price (Especially for branded items — often still better elsewhere)