Price Per Unit Calculator

Behind the number

Price per unit is total price divided by the quantity, expressed in whatever measure makes comparison possible: per item, per 100g, per litre, per wash, per use.

Choosing the denominator is the whole exercise. The same two products compared per pack and per 100ml can rank in opposite orders, which is exactly why unit pricing is mandated in many jurisdictions for grocery and why shelf labels carry it.

A real example

Product A: 250ml for $12.99, which is $5.20 per 100ml. Product B: 400ml for $18.99, which is $4.75 per 100ml. Product C: 1 litre for $42, which is $4.20 per 100ml.

The largest size is cheapest per unit, which is the expected pattern. But it is not universal, retailers frequently price the middle size worst, because it sits where the most shoppers look and price comparison is least common.

For a seller, the pattern to check is your own ladder. If your 400ml is worse value per 100ml than your 250ml, customers who check will feel misled and those who do not will buy the small one.

The usual mistakes

Unit price ignores everything except quantity. A concentrated product at a higher price per 100ml may be cheaper per wash; a product with better performance may need less. Unit price makes commodities comparable and makes differentiated products look expensive.

It also ignores waste. A larger pack that goes off before it is finished is not cheaper per unit consumed, only per unit purchased, and for perishables that gap can reverse the comparison entirely.

Using the result

Audit your own size ladder for consistency. Every step up should offer better value per unit, or the ladder tells customers that buying more is a worse deal, which is the opposite of what a size range is for.

Where a product genuinely delivers more per unit of measure, express the price in the unit that shows it. Per wash rather than per litre, per serving rather than per gram. That is not a trick if the claim is true, and it is the only way a concentrated or higher-performing product competes against a cheaper diluted one.

Designing a size ladder that works

A good ladder has three properties: each size is meaningfully different in quantity, each step offers better unit value than the one below, and the middle size is the one you most want to sell.

The middle-size point is deliberate. Given three options, buyers disproportionately choose the middle: the small looks mean, the large looks like a commitment, and the middle feels sensible. That effect is robust enough that the range should be designed around which product occupies that position.

The mistake to avoid is a ladder where the sizes are too close together. A 250ml and a 300ml give the customer a decision with no obvious answer, which slows the purchase and produces no benefit. Steps of roughly 1.6× to 2× in quantity are large enough to be a genuine choice.

Unit pricing is a legal requirement for many goods in the UK and EU, which is why shelf labels carry a price per kilogram or per litre. It exists because pack sizes are chosen to make comparison difficult, and shrinkflation, where the pack shrinks while the price holds, is visible in the unit price and invisible in the shelf price. It is the single most useful number on a supermarket label.