UtilibyWritten by the Utiliby editorial team · Last updated October 17, 2026 · Rules and formulas reviewed October 2026
What this free unit price calculator does
Supermarket shelves are designed to make comparing prices hard. Packs come in odd sizes, multipacks mix counts and sizes, and units jump between ounces, pounds, grams and litres. A unit price calculator removes the guesswork by converting everything to a price per standard unit, so you can see which product is really cheapest.
This free online tool compares up to six products at a time by weight, volume or count. It understands multipacks, converts between US and metric units automatically, names the best value, shows how much more each alternative costs and calculates your saving for the amount you plan to buy. A bar chart makes the winner obvious. Two extra tabs give you a cost per use and break-even calculator and a shrinkflation checker that shows the true price rise when a package gets smaller. Everything runs in your browser.
How to use the unit price calculator
- Choose what you compare by: weight, volume or count.
- Pick the price unit you want to see, such as per ounce or per litre.
- Enter each product with its price, size and unit. For a multipack, put the pack count in the Packs box.
- Read the best value at the top and the percent each other product costs extra.
- Add the total you need to see the money saved by choosing the best option.
- Use the other tabs for cost per use and shrinkflation.
The unit price formula
Unit price equals total price divided by total quantity. For three cereals, Brand A costs $4.49 for 12 oz, which is $0.3742 an ounce. Brand B costs $6.29 for 20 oz, or $0.3145 an ounce. The store brand costs $3.29 for 8.5 oz, or $0.3871 an ounce. Brand B is the best value even though it has the highest sticker price. Brand A costs 19.0 percent more per ounce and the store brand 23.1 percent more.
| Product | Price | Size | Per oz | Per lb |
|---|---|---|---|---|
| Brand A | $4.49 | 12 oz | $0.374 | $5.99 |
| Brand B | $6.29 | 20 oz | $0.315 | $5.03 |
| Store brand | $3.29 | 8.5 oz | $0.387 | $6.19 |
Converting between units
Products are labelled in many units. The calculator converts to a common base before dividing. One ounce is 28.35 grams, one pound is 453.59 grams, one US fluid ounce is 29.57 millilitres, and a US gallon is 3,785.41 millilitres. Count units cover single items, dozens and pairs. UK and US fluid ounces and pints differ, and the tool uses US measures, so check a label if you buy imperial units outside the US.
Multipacks and bulk buys
A multipack of 6 cans at 330 ml each holds 1,980 ml. At $4.99 it works out to about $2.52 a litre, which you can compare against a 2 litre bottle at $1.99, or $1.99 a litre. Larger bulk packs usually have lower unit prices, but not always, and a promotion on a small pack can beat the big one. Use the total-needed box to turn a unit price difference into real money saved on your shopping.
Shrinkflation and the price of less
Shrinkflation is when a product gets smaller while the price stays the same or rises. A 16 oz package at $4.99 that becomes 14.5 oz at $4.99 loses 9.4 percent of its contents. The unit price jumps from $0.312 to $0.344 an ounce, up 10.3 percent, with no change on the shelf label. The shrinkflation tab compares old and new price and size, so you can see the effective increase and decide whether to switch.
Cost per use and break-even
Unit price is not only for groceries. Cost per use tells you the real price of anything you use repeatedly, from a reusable bottle to a gym pass. A $60 item used 40 times costs $1.50 per use. If the alternative costs $4.50 each time, you break even after 60 / 4.50, about 14 uses, and at 3 uses a week it takes about 4.4 weeks. The tab does this calculation and shows whether your expected use makes it worthwhile.
Tips for finding the best value
- Compare in the same unit, not sticker prices.
- Check the shelf label, but verify it against your own numbers.
- Consider waste. A bulk item you cannot finish is not cheaper.
- Watch for shrinkflation on favourite products.
- Include sales and coupons in the final price you enter.
- Compare store brands. They are often the best value per unit.
Accuracy, privacy and responsible use
Results depend on the numbers you enter. The tool uses US measures for fluid ounces, cups, pints, quarts and gallons. It does not account for quality, nutrition, brand, expiry date or storage. A lower unit price is only a better deal if you will use the product. Nothing you enter leaves your browser.
Related free tools
Use these free online tools together with this one:
- Work out the price after a sale or coupon with the discount calculator.
- Find the percent difference between prices with the percentage calculator.
- Share a group shop fairly with the split bill calculator.
- See the yearly cost of recurring plans with the subscription cost calculator.
- Cost a recipe from ingredient prices with the recipe cost calculator.
Frequently asked questions
What is a unit price?
The price of one standard unit of a product, such as per ounce, per pound, per litre or per item. It lets you compare packs of different sizes fairly.
How do I calculate unit price?
Divide the price by the quantity. A $4.49 box holding 12 oz costs 4.49 / 12 = $0.374 per oz, or about 37.4 cents.
How do I compare two products with different sizes?
Work out the unit price of each in the same unit and pick the lower one. If the units differ, such as ounces and grams, convert first. This calculator converts automatically.
Is the bigger pack always cheaper per unit?
Not always. Bulk packs are often cheaper per unit, but promotions, store brands and sale prices can make a smaller pack the better value. Compare the unit prices.
How do I compare multipacks?
Enter the size of one item and the number of packs. A 6-pack of 330 ml cans at $4.99 is 1,980 ml in total, or about $2.52 per litre.
Can I compare different units such as ounces and pounds?
Yes. Pick a unit for each product from the list and the calculator converts everything to a common base before comparing.
What units does it support?
Weight in grams, kilograms, ounces and pounds. Volume in millilitres, litres, US fluid ounces, cups, pints, quarts and gallons. Count in items, dozens and pairs.
How do I compare price per 100 g or per kg?
Choose the weight category and set Show price to per 100 g or per kg. Many European shelf labels use these.
What is shrinkflation?
When a package gets smaller but the price stays the same or rises. The checker compares old and new unit prices. A 16 oz pack shrinking to 14.5 oz at the same price raises the unit price by about 10.3%.
What is cost per use?
The price of an item divided by the times you use it. A $60 item used 40 times costs $1.50 per use. It helps judge whether buying beats an alternative.
What is the break-even number of uses?
The number of uses at which the item costs the same as the alternative. A $60 purchase beats a $4.50 alternative after 14 uses.
Does the cheapest unit price always mean the best deal?
No. Consider quality, shelf life, storage space, waste and whether you will use it all. A cheap bulk item you throw away is not a bargain.
How do I compare grocery items in different shops?
Enter each shop's price and size as a separate product in the same category and compare the unit prices.
Does the tool include sales tax or deposits?
No. Enter the final shelf price you will pay, including any deposits, if you want them counted.
Can I use it for non-food items?
Yes. Use the count category for items such as paper sheets, pods or batteries, or weight and volume for liquids and powders.
Is my data stored or sent anywhere?
No. Everything runs in your browser.
Is this unit price calculator free?
Yes. It is free to use online with no sign-up.
Sources and further reading
- National Institute of Standards and Technology, SI units and conversions.
- National Institute of Standards and Technology, Guide for the Use of the International System of Units (SP 811).
- U.S. Bureau of Labor Statistics, Consumer Price Index.
- Federal Trade Commission, Consumer advice.
Sources were consulted in October 2026. Standards and rules can change, so always check the official page for your situation.