Unit Price Calculator
Enter the price and size of two products in the same unit (both in ml, both in grams, or both by count) to see the true price per unit for each, which one is cheaper, and by how much.
How this calculation works
Unit price is simply price divided by size: unit price = price ÷ size. This gives you a cost per single unit — per millilitre, per gram, per sheet, per item — so you can compare packages of different sizes on equal footing.
The calculator computes the unit price for Option A and Option B separately, then flags whichever number is lower as the cheaper option. If both come out identical, it reports a tie.
Savings percent compares the two unit prices: it takes the higher unit price, subtracts the lower one, and divides by the higher one. That tells you what fraction of the pricier option's cost you avoid by buying the cheaper one, per unit.
Worked example
Why bigger isn't always cheaper
It's tempting to assume the largest package always offers the best value, but pricing rarely scales in a straight line. Retailers set prices based on demand, shelf position, promotions, and packaging cost — not a fixed per-unit rate. A "jumbo" size is sometimes discounted to move volume, but it's just as often priced at a premium because shoppers expect it to be cheaper and don't check.
The only reliable way to know which option is the better deal is to divide price by size for each and compare the results directly, which is exactly what this calculator does.
Reading store unit-price labels
- Shelf labels often show a standardized unit price (e.g. "per 100 g" or "per litre") set by local regulation — check whether both items use the same base unit before comparing them by eye.
- Rounding on printed labels can hide small differences; recompute with exact prices and sizes when two items look close.
- Sale or loyalty-card prices are usually not reflected in the shelf unit-price tag, so factor in the discount price of the item, not the sticker price, for an accurate comparison.
- Multi-buy deals (e.g. "3 for 10") change the effective per-item price — divide the deal price by the total quantity across all items before comparing.
Common bulk-buying traps
| Trap | What happens | How to avoid it |
|---|---|---|
| Premium "family size" | Larger pack costs more per unit than the standard size | Always check the per-unit price, don't assume size = savings |
| Mismatched units on labels | One item is priced per ounce, another per gram or per 100 ml | Convert both to the same unit before comparing |
| Multi-buy offers | "Buy 2 get 1 free" changes the real per-item cost | Divide the total deal price by total quantity, not the single-unit price |
| Concentrated products | A smaller bottle of concentrate may cover the same number of uses as a larger diluted one | Compare cost per use or per diluted volume, not just per ml of concentrate |
When unit price isn't the whole story
Unit price is a strong signal but not the only factor worth weighing. If a product spoils before you can use it all, buying the larger, cheaper-per-unit size can end up costing more in waste. Storage space, shelf life, and how often you'll actually restock also matter — the lowest price per unit only pays off if you use what you buy.