Shopping calculations
How to calculate unit price
Divide the total purchase price by the total quantity. Convert competing packages to the same unit before deciding which has the lower price per unit.
Open the unit price calculatorUnit price = total price ÷ total quantity
Compare two package sizes
Compare a 500 g package for $3 with a 1 kg package for $5.
- Convert 500 g to 0.5 kg.
- First package: $3 ÷ 0.5 kg = $6 per kg.
- Second package: $5 ÷ 1 kg = $5 per kg.
The 1 kg package is cheaper per kilogram. Its unit price is $1 per kg lower, or 16.67% lower relative to the $6 comparison price.
| Package | Unit price | Cost for 1 kg |
|---|---|---|
| 500 g for $3 | $0.006 per g | $6 |
| 1 kg for $5 | $0.005 per g | $5 |
Handle multipacks
For six 330 mL cans costing $7.50, total volume is 6 × 330 = 1,980 mL, or 1.98 L. Unit price is $7.50 ÷ 1.98 = about $3.79 per liter.
Be clear whether the displayed size is per pack or for the whole bundle. Multiplying an already-total quantity by the pack count produces a wrong result.
Compare like with like
- Use the same currency and include or exclude tax consistently.
- Apply coupons and membership prices before dividing if they actually apply.
- Compare mass with mass, volume with volume, or count with count.
- Do not convert mass to volume without a known density.
A lower unit price is not automatically the better purchase. Consider quality, usable quantity, storage, expiry and whether buying more increases waste. Total spending can be higher even when unit price is lower.
Odd unit labels
Retail shelf labels may show price per 100 g, per ounce or per item. Normalize both products to one convenient basis. Price per 100 g is simply price per gram × 100. For counts, divide by the number of equivalent items.
Compare unit prices online
The free Unit Price Calculator compares multiple products across supported item, mass and volume units. Enter each total price, size per pack and pack count.