Compare two items by price per unit — enter each one's price and size to see which is actually the better deal.
Compare items in the SAME unit (both in oz, both by count, etc.). The lowest price per unit is the better value — before factoring in whether you'll use it all. General information.
A bigger package isn't automatically cheaper. Dividing price by quantity gives price per unit — the apples-to- apples number that tells you which option actually costs less.
Unit price = price ÷ quantity · Lower wins
Unit price does one job: it removes package size from the comparison so you are looking at the only number that is actually comparable. Price alone tells you what leaves your wallet today; price per unit tells you what you are paying for the thing itself. Shops know this, which is why the shelf label carries it in small print and the promotion carries the headline price in large print.
Item A is $4.50 for 16 units; item B is $7.20 for 28. Divide each and you get $0.2813 and $0.2571 per unit — the calculator shows four decimal places deliberately, because at these sizes the third decimal is where the answer lives. B wins by $0.0241 a unit. That gap sounds like nothing until you scale it: across 100 units it is $2.41, and as a percentage B is 8.6% cheaper than A for the same stuff.
Put it the other way round, which is often how the decision actually presents itself. To get B's 28 units by buying A, you would need 1.75 packs — $7.88 against B's $7.20, so buying small costs you $0.67 for the same quantity. And you cannot buy 0.75 of a pack, so in practice you would buy two at $9.00 and hold 4 spare units.
A unit price is only real if the units get used. Run the break-even: B beats A only while its effective unit price stays under A's $0.28125 (the page rounds the display to $0.2813), and $7.20 ÷ 0.28125 = 25.6. So you must consume at least 25.6 of B's 28 units — 91.4% of the pack — before the saving evaporates. Throw away four units and B's effective price is $0.3000, now worse than A. Throw away a quarter of it and you have paid $0.3429 a unit for the privilege of buying in bulk. That is the whole bulk-buying trap in one line of arithmetic, and it is why perishables and bulk deals are a bad pairing.
Mixing units is the big one: comparing a 500 g bag against a 20-count box produces two numbers that cannot be compared, and the calculator has no way to know. Convert first, and be suspicious of packaging that quotes weight on one product and count on the other — that is sometimes deliberate. Second, watch for a size that is not what it looks like: a "family pack" that is two half-size units, or a concentrate that makes twice as much as the ready-mixed version, needs to be compared on what it yields, not what it weighs. Third, remember that anything you pay on top — delivery, a minimum order, the petrol to reach the warehouse store — belongs in the price before you divide. And fourth, a lower unit price on something you would not otherwise buy is not a saving at all.
One comparison is a calculation; buying supplies for a business is a record. What actually saves money there is a sheet with one row per item and columns for vendor, pack size, price, unit price and date — because then you can see that a vendor quietly raised the pack price while holding the headline, or that the cheaper supplier is only cheaper above a minimum order. Our small business bookkeeping template gives supply costs a home next to the rest of your numbers. If you are pricing what you sell rather than what you buy, the markup calculator works the other direction, and the ecommerce profit calculator puts unit cost and fees together.
Yes — compare ounces to ounces or count to count. Mixing units makes the per-unit prices meaningless.
Only if you'll use it. A bulk deal you throw half of away isn't a saving — factor in waste and shelf life.
Related: ratio calculator · markup calculator · ecommerce profit calculator · all free calculators.
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It uses standard formulas and recalculates the moment you change a value, so the math is exact for the inputs you enter. Treat the result as a reliable planning estimate; for decisions with legal or tax consequences, confirm the figures with a qualified professional.
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Last reviewed: September 2026. Free to use, no signup — Unit Price Calculator by ToolWise Digital.
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