Unit Price Calculator guide
Enter the price and size of two options and see the cost per unit for each, which one wins, and how much cheaper it is in percent. Stop trusting the shelf tag and the word "value" on the box.
How the comparison works
You fill in two options, A and B. Each gets a price, a quantity, and an optional unit label like oz, count, sheets, or loads. The calculator divides price by quantity for each one, shows the price per unit, tells you which is cheaper, and says by how much in percent.
The formula is as simple as it gets: unit price = price / quantity. The value is in doing it for both products in two seconds while you stand in the aisle, with enough decimals to see a real difference. Unit prices show up to 4 decimal places where needed, because a lot of everyday products cost fractions of a cent per unit.
Example: pasta sauce
Option A: a 16 oz jar for $4.99. Option B: a 28 oz jar for $7.49. A costs $4.99 / 16 = $0.3119 per ounce. B costs $7.49 / 28 = $0.2675 per ounce. B is cheaper by (0.3119 - 0.2675) / 0.3119, about 14.2 percent per ounce.
Now add a $1 coupon on the small jar. A drops to $3.99 / 16 = $0.2494 per ounce, and it beats B. Always enter the price you will actually pay at the register.
Example: when per-roll pricing lies
Paper towels are the classic trap. A: 12 "double" rolls for $15.99. B: 6 "mega" rolls for $11.49. Per roll, A is $1.33 and B is $1.92, so A looks like a steal.
But roll sizes differ. Check the sheet count on the package: say A has 1,320 sheets total and B has 990. Per sheet, A is $0.0121 and B is $0.0116. B is about 4 percent cheaper. The unit you choose decides the answer, so pick the unit that measures what you actually use: sheets for towels, loads for detergent, ounces for food, count for batteries.
Why you cannot always trust the shelf tag
Many US grocery stores print a unit price on the shelf label, but there is no single national rule for how. NIST Handbook 130, published by the National Institute of Standards and Technology, includes a Uniform Unit Pricing Regulation that states can adopt, but it is voluntary at the federal level. Some states and cities require unit pricing, many do not, and the rules on which units to use vary.
The result: you will see one brand priced per ounce and the one next to it priced per pound, or per count on one tag and per ounce on the other. Sale tags often show the regular unit price, not the sale one. Doing the math yourself with the same unit on both sides is the only way to be sure.
Mistakes that cost money
Mixing units. 1.5 lb and 20 oz are not comparable until you convert: 1.5 lb is 24 oz. Use the same unit for both options, and use the unit converter if you need to.
Assuming bulk is cheaper. It usually is, but stores know shoppers assume that. A 12 oz bag of coffee at $3.49 ($0.2908 per ounce) beats a 24 oz bag at $7.29 ($0.3038 per ounce).
Ignoring waste. The cheapest unit price is only cheaper if you use it all. A giant tub of spinach at half the per-ounce price is a bad deal if half of it goes in the trash. Same for anything with a short shelf life.
Comparing across concentrations. Concentrated detergent and regular detergent should be compared per load, not per fluid ounce.
Beyond groceries
The same math works anywhere a price comes in different sizes: price per GB for phone plans and storage, price per month for annual versus monthly subscriptions, price per pod for coffee, price per diaper, price per dose for vitamins. If two things can be counted in the same unit, this calculator settles which one is the better deal.
How we calculate: sources
Frequently asked questions
How do you calculate unit price?
Divide the price by the quantity. A $4.99 jar of 16 oz costs $4.99 / 16 = $0.3119 per ounce.
Is the bigger package always cheaper per unit?
No. It usually is, but not always. A 12 oz bag of coffee at $3.49 costs $0.2908 per ounce, while a 24 oz bag at $7.29 costs $0.3038, so the smaller bag is about 4% cheaper per ounce.
How is the percent cheaper calculated?
It compares the two unit prices: (higher unit price - lower unit price) / higher unit price x 100. If one costs $0.30 per ounce and the other $0.27, the cheaper one is 10% less per ounce.
Why does the calculator show 4 decimal places?
Unit prices are often fractions of a cent. $0.0121 and $0.0116 per sheet both round to 1 cent, but that gap is a 4% difference you would miss at 2 decimals.
What if the two products use different units?
Convert them to the same unit first. Compare ounces to ounces or count to count. If one is in pounds, multiply pounds by 16 to get ounces before entering it.
Should I include coupons and sales?
Yes. Enter the price you will actually pay after coupons, sales, and loyalty discounts. A $1 coupon can flip which option is the better deal.
Is my data kept private?
Everything runs in your browser. Nothing you enter is uploaded to a server or stored by us.
How do I compare an annual subscription to a monthly one?
Enter the annual price with a quantity of 12 and the monthly price with a quantity of 1, using month as the unit. A $99 annual plan is $8.25 a month, 17.5 percent less than a $10 monthly plan.
Do US stores have to show unit prices?
Not everywhere. There is no single national requirement. Some states and cities mandate unit pricing, and NIST Handbook 130 offers a voluntary model regulation.