Free unit price tool
Unit Price Calculator: Compare Price per kg, Litre or 100 Items
A unit price calculator divides a selling price by the total quantity in a standard unit, such as kilograms, litres or 100 items. Enter two multipack offers and this tool shows which one costs less per unit, how much you save per kg or L, and the percentage saved. It also checks whether a smaller pack hides a price rise.
Supermarket shelf tags do not always show a fair comparison. Pack sizes vary, discounts change the real price, and a pack that looks identical can hold less. This calculator converts every weight to grams and every volume to millilitres, so the result is always fair.
Why shelf prices mislead
Three numbers that show how package sizes hide price rises
Manufacturers often keep the shelf price and cut the contents. The price per unit is the only fair test, and these three cases show the size of the effect.
Price per ounce rise when a half-gallon of ice cream at $5.99 drops to 60 oz with no price change.
Effective price rise when a $2.50 pack falls from 500 g to 450 g.
Saving per kg in the worked example, where a 750 g pack at $3.29 beats two 500 g packs at $4.99.
Calculator
Compare two offers by price per kg, L or 100 items
Enter each offer. Both offers must use the same measure type: weight with weight, volume with volume, or item count with item count.
Methodology
How is the unit price calculated?
The unit price divides the net price by the total quantity in a standard unit. Weight converts to grams and kilograms, volume converts to millilitres and litres, and items convert to a price per 100 items.
Worked example
What does a 750 g pack save against two 500 g packs?
Offer A is two 500 g packs at 4.99, so the total is 1 kg and the unit price is 4.99 per kg. Offer B is one 750 g pack at 3.29, so the unit price is 3.29 divided by 0.75, which is about 4.39 per kg. Offer B is cheaper. You save about 0.60 per kg, or 12.1% compared with Offer A.
Reference values
What do common pack changes do to the unit price?
| Scenario | Before | After | Result |
|---|---|---|---|
| Shelf price unchanged, pack shrinks | 2.50 for 500 g (0.005 per g) | 2.50 for 450 g (0.00556 per g) | Effective price up 11.1% |
| Ice cream, same price, smaller tub | 5.99 for 64 oz | 5.99 for 60 oz | Price per ounce up 6.7% |
| Two 500 g packs against one 750 g pack | 4.99 per kg | About 4.39 per kg | Save about 0.60 per kg (12.1%) |
| Unit conversion, weight | 1 kg | 1,000 g | Base for all weight results |
| Unit conversion, volume | 1 L | 1,000 ml | Base for all volume results |
Questions
Unit price questions, answered
Each answer starts with the direct result. The details follow.
How do I compare two packs of different sizes?
Divide each selling price by its total quantity in the same unit, then compare the two results. Enter both offers above and the calculator does this for you, scaled to price per kg, price per L or price per 100 items.
Can I compare grams with millilitres?
No. The calculator blocks weight against volume or item count, because converting between them needs the product density, which a shelf label does not show.
How do I enter a discount?
Enter the amount off the selling price in the same currency. The calculator subtracts it before dividing. A discount cannot be negative or equal to or above the selling price.
What is shrinkflation, and how do I measure it?
Shrinkflation is a smaller pack at the same price. Enter the old and new price and quantity in the Old versus new package tab. The effective price change shows how much the price per unit rose, even if the shelf price did not move.
Why does the unit price show three decimals below 1?
Values under 1 need a third decimal so that close prices, such as 0.005 and 0.0056 per gram, remain distinct.
Start comparing
Find the cheaper pack before you reach the till
Enter two offers and get the price per kg, L or 100 items in seconds. No sign-up, no data stored.