Unit Price Calculator

How the unit price is calculated

Unit price is the package price divided by the package size, in whatever unit you are using for both products. Product A costs price A ÷ size A. Product B costs price B ÷ size B. The lower number is the better deal per unit. The panel also states how much cheaper the winner is, as a percent of the more expensive unit price: (higher − lower) ÷ higher × 100, rounded to one decimal place. Unit prices themselves are rounded to four decimal places, which is enough to separate prices that look identical in cents and still too coarse to be a cash-register total.

The unit menu (ounce, pound, gram, milliliter, item, serving, and the rest) is a label. It does not convert. If you tell the page that both sizes are ounces, it divides price by the numbers you typed and prints "per oz." It will not turn pounds into ounces, or fluid ounces into milliliters, or a count of sheets into square feet. Both sizes must already be in the same unit before you compare them. A tie, the same cost per unit after that division, is reported as a tie.

Worked examples

Example 1: Two bags of coffee

Product A is $9.99 for 12 ounces. Product B is $11.99 for 16 ounces. Set the label to ounce. A is 9.99 ÷ 12 = $0.8325 per ounce. B is 11.99 ÷ 16 = $0.7494 per ounce after the page rounds to four decimals. B is cheaper. The percent uses the unrounded values and comes out to 10 percent cheaper per ounce: the gap divided by A's unit price. The bigger sticker, $11.99, is the better buy per ounce in this pair. The smaller sticker is the more expensive coffee.

Example 2: A sale that flips the usual pattern

The 16-ounce bag is still $11.99. The 12-ounce bag is on sale at $8.40. Then A is 8.40 ÷ 12 = $0.70 per ounce, and B is still about $0.7494. The smaller bag wins. "Bigger is cheaper" is a habit, not a rule. A temporary price on the small size, a club-store markup on the bulk size, or a family pack that is not actually a discount can reverse the ranking. Run the division whenever the sizes differ.

Example 3: Same brand, price per item

A 24-count box is $5.49 and a 36-count box is $7.99. Label the unit "item" and enter 24 and 36 as the sizes. A is 5.49 ÷ 24 = $0.2288 per item. B is 7.99 ÷ 36 = $0.2219 per item. B is only a little cheaper per count. If you will throw away the extra twelve because they go stale, the lower unit price is not the lower cost to you. The calculator compares the packages as priced. It does not know what you will use.

Example 4: Comparing after a percent-off coupon

Unit price belongs on the price you will actually pay. If a 20 percent coupon applies to the larger box and not the smaller one, convert that box to its sale price first with the Percent Off Calculator, then bring the sale price here. Comparing the pre-coupon sticker with a competitor's sale price mixes two different offers.

When to use this

Use it in the aisle when two packages of the same product come in different sizes, and again at home when a shelf tag looks suspicious. Grocery, paper goods, pet food, detergent, and warehouse-club packs are the usual cases. It is also the right check on a contractor's material quote when one supplier sells a 450-square-foot pallet of sod and another sells a 500-square-foot pallet: enter each price and each coverage, label the unit square feet, and read cost per square foot. The same pattern works for any two prices that share a unit.

It is the wrong tool when the products are not substitutes. A cheaper price per ounce of a different roast, a lower grade of olive oil, or a paper towel with fewer sheets per "square foot" of a different ply is a quality decision the division cannot make. Get the unit price first so the quality difference has a real price attached to it.

The unit has to match

Shelf tags sometimes switch units between neighboring products, one per pound and one per ounce, or one per 100 sheets and one per roll. This page will faithfully divide whatever you type. If you enter 2 for a two-pound bag and 32 for a 32-ounce bag and call both "pounds," the 32-ounce bag looks enormous and cheap. Convert first. Two pounds is 32 ounces, so both sizes should be entered in ounces, or both in pounds. The Weight Converter and the Volume Converter do that conversion. Kitchen cups and spoons, when the "size" is a recipe measure rather than a package net weight, belong in the Cooking Measurement Converter.

Watch count versus measure. Toilet paper priced per roll hides a roll that is shorter. Price per sheet, or per square foot if that is what the package states, is the comparison that matches how you use it. Vitamins priced per bottle hide a bottle of 60 tablets next to a bottle of 200. Use the count as the size and the label "item." Beverages priced per bottle hide a 12-ounce can next to a 2-liter. Use fluid ounces or milliliters for both, after you convert.

Common mistakes

• Different units in the two size fields. The label does not convert. Ounces against pounds, or items against ounces, produces a number and the wrong winner.
• Using the pre-sale price on one item. Divide the price you will pay, including a coupon that actually applies to that package and excluding a coupon that does not.
• Forgetting a deposit or a fee that one package carries. Add the bottle deposit or the per-item fee into the price before you divide, if you want the out-the-door unit cost.
• Comparing a multipack's count with a single's weight. Pick one basis, count or weight, and put both products on it.
• Reading the percent as savings off the package price. The percent is how much lower the winning unit price is, relative to the losing unit price. It is not "percent off" the sticker.
• Ignoring waste. A lower unit price on food you will not finish can cost more. The math stops at the package.
• Trusting a shelf tag that uses a different unit than the one in your head. Read the tag's unit, then rerun the numbers in that same unit so you can see whether the tag matches the package.

Limitations

Two products, one shared unit, no tax table, and no automatic unit conversion. The page does not know whether the goods are equivalent, whether a bulk package will fit in the cabinet, or whether a warehouse membership fee should be spread across the year. Prices round to four decimals on screen. Very small unit prices, such as a fraction of a cent per sheet, can look similar after that rounding even when the percent line still separates them. Read both lines. There is no third product. Compare the winner with the next candidate in a second pass. A paint quantity is not a package size this page knows. After how many gallons of paint for a 12x12 room (or the paint calculator) tells you the gallons, compare two prices per gallon here.

FAQ

Why does the percent say 10 when my mental math was a little under 10?

The percent is rounded to one decimal, and a value just under 10 can display as 10. The four-decimal unit prices are the figures to compare if you are checking a close race. In the coffee example, $0.8325 versus $0.7494 is the more precise statement, and the percent is the rounded summary.

Should I include tax?

If both items are taxed the same way, tax scales both prices by the same factor and the winner does not change. If one item is taxed and the other is not, put the tax into the price of the taxed item before you divide.

What if the sizes are on the package in different units?

Convert one size into the other's unit first, then come back and divide. The dropdown only names the unit you have already matched.

Is the bigger package usually cheaper per unit?

Often, and often enough that people stop checking. Example 2 is the case where a sale on the small package wins. Check when the prices are close, when one item is on promotion, or when the "family" size looks oddly expensive.

Can I compare three sizes of the same cereal?

Pair them. Compare small with medium, then the winner with large, using the same unit each time. The page holds two products.

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• Cooking Measurement Converter for cups and spoons
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• How many gallons of paint for a 12x12 room before you compare price per gallon
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