Unit Price Calculator

Comparing what things actually cost

Unit price is total price divided by quantity — cost per gram, per millilitre, per sheet, per item. It's the only reliable way to compare packages of different sizes, and it's the number supermarket shelf labels bury in six-point type.

Bigger isn't automatically cheaper

Bulk sizes usually offer a lower unit price, but the exception is common enough to be worth checking every time. Promotions on smaller packs regularly beat the bulk rate, and some categories price large sizes at a premium because shoppers assume the saving is there.

Three things worth weighing against a lower unit price:

• Waste. A cheaper unit price on more food than you'll use before it spoils is not a saving.
• Storage. Bulk needs somewhere to live.
• Cash flow. Spending 40 to save 3 isn't always the right call this week.

Convert to a common unit first

Comparing 500 g against 1.2 kg means putting both in the same unit. Move everything to the smaller one — grams, millilitres, individual items — and the comparison becomes direct. The calculator does the division, but it can't know that your two numbers are in different units.

Where the difference is worth chasing

Unit-price comparisons pay off most on things you buy constantly: staples, cleaning products, pet food, nappies, coffee. A 15% saving on a weekly purchase compounds across the year in a way that the same saving on a one-off doesn't.

For an occasional purchase, the few minutes of comparison are usually worth less than the money saved. Concentrate the effort where the repetition is.