Option A
Option B
Better value
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Option A per unit—
Option B per unit—
Calculations run entirely in your browser. Nothing is sent anywhere.
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Why price-per-unit beats the sticker price
Retailers price products in pack sizes that make direct comparison hard on purpose. A larger pack usually costs less per unit, but not always — promotions, premium packaging and 'bonus' sizes can flip the maths. Calculating cost per unit (per litre, per kilogram, per sheet, per count) is the only reliable way to compare value.
This works for almost anything sold in varying sizes: groceries, batteries, printer ink, cleaning supplies, building materials, even storage and subscriptions. Compare on the same unit and the cheaper option becomes obvious.
How to use it
- Enter the price and the size/quantity for each option (use the same unit for both — e.g. both in ml, or both in grams, or both as a count).
- The calculator shows the cost per unit for each and highlights the better-value choice and how much you save per unit.
- Tip: convert to the same unit first (1 L = 1000 ml, 1 kg = 1000 g) so the comparison is fair.
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Frequently asked questions
How do I calculate price per unit?
Divide the price by the size or quantity. For example, a 750 ml bottle at $6 costs $6 ÷ 750 = $0.008 per ml (0.8 cents). To compare two products, calculate this for both using the same unit, and the lower number is the better value. This calculator does the maths for you and highlights the cheaper option.
Is the bigger pack always cheaper per unit?
Usually, but not always. Larger sizes often have a lower unit price thanks to economies of scale, but promotions on smaller packs, premium 'travel' sizes, and marketing 'bonus' packs can reverse this. The only way to be sure is to calculate the cost per unit for each option rather than assuming bigger is better.
What units can I compare?
Anything, as long as you use the same unit for both options. Common examples are cost per litre or millilitre for liquids, per kilogram or gram for solids, per sheet for paper products, and per count for items like batteries or capsules. Convert both options to the same unit first for a fair comparison.