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Unit Price Calculator
Find the cheaper buy with this free unit price calculator. Enter the price and size of two products, pick the unit they share, and it works out the price per unit for each one — then tells you which is cheaper and exactly how much you save per unit.
Unit conversions to remember
| Convert | Multiply by | Example |
|---|---|---|
| Pounds to ounces | 16 oz per lb | 2 lb = 32 oz |
| Kilograms to grams | 1,000 g per kg | 0.5 kg = 500 g |
| Liters to milliliters | 1,000 mL per L | 1.5 L = 1,500 mL |
| Fluid ounces to mL | 29.5735 mL per fl oz | 12 fl oz = 354.88 mL |
How it works
Unit price is the price of one unit of a product — one ounce, one gram, one item — and it is the only fair way to compare two packs of different sizes. A $7 pack is not automatically a worse deal than a $4.50 pack if it holds nearly twice as much. The calculation is a single division: unit price equals price divided by quantity. So a $4.50 pack of 12 ounces costs $4.50 ÷ 12 = $0.375 per ounce, and a $7 pack of 20 ounces costs $7 ÷ 20 = $0.35 per ounce. The second pack is cheaper per ounce, even though it costs more at the till.
The one rule that makes the comparison honest is that both products must be measured in the same unit. Comparing a price per ounce with a price per pound is meaningless until one of them is converted — there are 16 ounces in a pound, so $0.35 per ounce is $5.60 per pound. That is why this calculator uses one shared unit for both products: pick ounces, pounds, grams, kilograms, fluid ounces, milliliters, liters, or "each" for items sold by count, and enter both sizes in that unit. If the packs are labeled in different units — one in pounds and one in ounces, for example — convert the odd one first using the table above, then compare.
Once both unit prices are known, the winner is simply the lower one, and the saving is the difference between them. In the example above, the saving is $0.375 − $0.35 = $0.025 per ounce. That sounds small, but it scales with how much you buy: on 20 ounces it saves $0.50, and on 100 ounces it saves $2.50. The calculator shows that scaled saving for the larger pack size, so you can see whether the difference is worth caring about or just a few cents. When the unit prices come out equal, neither product wins — buy whichever you prefer, or the smaller pack if you might not finish it.
Supermarkets often print the unit price on the shelf label, in small print under the pack price, and it is worth learning to read it — it is the same number this calculator produces. But shelf labels are not always in the unit you want, and they are not always there at all, which is when a quick calculation on your phone pays for itself. The most common trap is the "value pack" that costs less per pack but more per unit than the regular size, and the second trap is comparing different brands where one pack includes more packaging and less product. In both cases, the unit price cuts through the marketing: divide, compare, and let the smaller number win.
Worked example
Two packs of the same coffee are on the shelf. Pack A costs $4.50 for 12 ounces, and pack B costs $7.00 for 20 ounces. Which is the better buy?
Step 1: Work out A's unit price — $4.50 ÷ 12 oz = $0.375 per ounce.
Step 2: Work out B's unit price — $7.00 ÷ 20 oz = $0.35 per ounce.
Step 3: Compare — $0.35 is less than $0.375, so B is cheaper per ounce.
Step 4: Find the saving — $0.375 − $0.35 = $0.025 per ounce.
Step 5: Scale it up — on 20 ounces, B saves 20 × $0.025 = $0.50.
Enter the same numbers in the calculator above and it gives exactly the same result: A $0.375/oz, B $0.35/oz, B cheaper by $0.025/oz. Try a case where the bigger pack loses: $5 for 10 ounces is $0.50 per ounce, while $9 for 16 ounces is $0.5625 per ounce — the smaller pack wins, and the calculator will say so.
FAQ
How do you calculate unit price?
Divide the price by the quantity: unit price = price ÷ quantity. For example, $4.50 ÷ 12 oz = $0.375 per ounce. The calculator above does this for two products at once and compares them.
Which product is cheaper in the example?
Product B. A costs $0.375 per ounce and B costs $0.35 per ounce, so B is cheaper by $0.025 per ounce — a saving of $0.50 on 20 ounces.
Can I compare products sold in different units?
Only after converting them to the same unit. If one pack is labeled in pounds and the other in ounces, convert the pounds to ounces first (1 lb = 16 oz) and then compare. This calculator uses one shared unit for both products so the comparison stays fair.
Should I compare price per ounce or price per pound?
Either one works, as long as it is the same for both products — the winner is the same either way, because the two unit prices scale together. Use whichever unit is printed on the packs so you do not have to convert.
Does a lower unit price always mean the better buy?
Not always. A lower unit price is the better deal only if you will actually use the product before it expires or goes stale, and if you have somewhere to store it. For food that spoils, a slightly dearer small pack you finish beats a cheap big pack you throw half of away.