Unit Price Comparison Calculator
Work out which of two options is the better deal by price per unit — the classic 'is the bigger box actually cheaper?' check at the store. Enter each option's price and size in the same unit, and you'll see the price per unit for both and how much cheaper the winner is.
Enter values above to see the result.
What the calculator gives you
Enter a price and size for each of two options and you get:
- Better deal — which option is cheaper per unit, and by what percentage.
- Option A price per unit — its price divided by its size.
- Option B price per unit — the same for the other option.
A worked example
A $3.00 bag holds 12 oz, so it's $0.25 per ounce. A $5.00 bag holds 24 oz, so it's about $0.2083 per ounce. The bigger bag wins — it's about 16.7% cheaper per ounce, even though it costs more at the register.
Why price per unit matters
Stores list sizes and prices that are hard to compare at a glance — different pack counts, odd weights, "value" sizes that aren't. Reducing each to a single price-per-unit number puts them on the same footing, so you can see the real deal instead of guessing. Shelf tags sometimes show a unit price, but not always, and rarely for both the item and its rivals.
When you'll use it
Grocery shopping (cost per ounce or per 100 g), comparing bulk versus regular sizes, weighing a multipack against singles, or checking whether a bigger subscription tier is really better value per unit.
Frequently asked questions
What counts as a 'unit'?
Whatever you measure the size in — ounces, grams, liters, sheets, tea bags, whatever. The only rule is that both options use the same unit. Compare price per ounce to price per ounce, not ounces against pounds. If two products are sold in different units, convert one first so they match.
How is the better deal decided?
It divides each option's price by its size to get the price per unit, then picks the lower one. The 'percent cheaper' is measured against the pricier option — if A is $0.25 per unit and B is $0.2083, B is about 16.7% cheaper than A.
Is the bigger size always cheaper per unit?
Usually, but not always. Bulk sizes often have a lower unit price, but promotions, coupons, or odd package sizes can flip it — a sale on the small size can beat the big one. That's exactly what this calculator is for: checking instead of assuming.
Can I compare more than two options?
This compares two at a time. To rank several, compare them in pairs — check the winner of the first pair against the next option, and so on. The lowest price per unit always wins overall.
What if the two options are different units, like a 500 g bag and a 2 lb bag?
Convert them to the same unit first — turn the pounds into grams (or grams into pounds) — then enter both sizes in that unit. Otherwise the price-per-unit numbers aren't comparable.