Unit price calculator — find the real best value
Supermarket shelf labels often show a “price per unit” figure, but not every shop displays one, and it is easy to be misled by a bigger pack or a bright “special offer” sticker. This calculator puts any two or more products on the same per-unit basis — price per kg, per litre, per 100 g or per item — so you can see which one is genuinely the cheapest.
How it works
The unit price is (price ÷ quantity) × units-per-base-unit. Enter each option’s
shelf price and the quantity it contains, and set the base unit you want to compare
on. If you entered the quantity in grams but want the price per kilogram, set the
units-per-base-unit factor to 1000. The lowest result is highlighted as the best
value.
Worked example
A 500 g jar of coffee costs 4.20 and a 750 g jar of the same coffee costs 5.85.
- Small jar:
(4.20 ÷ 500) × 1000 = 8.40 per kg - Large jar:
(5.85 ÷ 750) × 1000 = 7.80 per kg
The larger jar is cheaper per kilogram, so it is the better value — but only by about 7%, which a promotion on the small jar could easily overturn.
| Product | Price | Quantity | Price per kg |
|---|---|---|---|
| Small jar | 4.20 | 500 g | 8.40 |
| Large jar | 5.85 | 750 g | 7.80 |
Practical tips
Watch the units on the label. Shops sometimes quote one product per 100 g and a neighbouring one per kg. Always convert both to the same unit before comparing — this tool does that for you.
Multi-buys and loyalty prices. Enter the actual price you will pay (after any multi-buy or member discount) so the comparison reflects your real cost.
Non-grocery uses. The same logic works for printer ink (price per ml), building materials (price per m²) or anything sold in different pack sizes.
All calculations run entirely in your browser — nothing is uploaded or stored.