Unit Price Calculator
Compare 2 to 6 items by price per ounce, pound, fluid ounce, liter or each. Converts units, flags the cheapest and shows the percent saved. No signup.
Enter the shelf price, then the size printed on the package. Buying a multipack? Put the size of one can or box and the number of packages. The values shown are sample figures.
| Item | Total size | Price | Per oz | Versus cheapest |
|---|---|---|---|---|
| Item A | 18 oz | $4.49 | $0.2494 | 6.6% more |
| Item B (cheapest) | 32 oz | $7.49 | $0.2341 | — |
| Item C | 52.911 oz | $13.50 | $0.2551 | 9.0% more |
The saving is measured against the most expensive item. Cheaper per unit only saves money if you use the whole package before it spoils or goes stale.
What Unit Price Calculator Does
A unit price is what you pay for one standard amount of a product: one ounce, one pound, one liter, one egg. Dividing the shelf price by the package size turns packages of different sizes into one number you can compare. This calculator does that for two to six items at once, converts between units that measure the same thing, marks the cheapest and shows how much less per unit it costs than the most expensive.
Conversion works inside three kinds of quantity. Weight covers ounces, pounds, grams and kilograms. Liquid volume covers fluid ounces, pints, quarts, gallons, milliliters and liters. Count covers single items and dozens, which also handles prices per sheet or per wash load if you enter the number of sheets or loads. A weight cannot be turned into a volume without the product’s density, so when items from different kinds are entered the calculator says so and does not rank them.
The conversion factors are the exact definitions published by NIST in Handbook 44 and SP 811, listed in the table below. The prices in the examples on this page are invented to show the arithmetic. They are not quotes from any store.
How to Use Unit Price Calculator
- Enter the shelf price, the size printed on the package and its unit for each item
- For a multipack, enter the size of one can or box and how many packages the price covers
- Add up to six items, or remove an item you do not need
- Choose the unit to compare per, such as ounce, pound, fluid ounce, liter or each
- Read the cheapest item, the percent saved against the most expensive one and each unit price in the table
Formula Used by Unit Price Calculator
Unit price
Total amount = size × packages; Unit price = price ÷ (total amount converted to the chosen unit)
- size
- The amount printed on one package, in its own unit
- packages
- How many identical packages the price covers (1 for a single item)
- conversion
- Multiply by the grams or milliliters in the package’s unit, then divide by the grams or milliliters in the chosen unit
Worked example
Three cereals: A is $4.49 for 18 oz, B is $7.49 for 2 lb, C is $13.50 for 1.5 kg. Compare per ounce.
- A: 4.49 ÷ 18 = $0.2494 per oz
- B: 2 lb × 16 = 32 oz, and 7.49 ÷ 32 = $0.2341 per oz
- C: 1.5 kg = 1,500 g ÷ 28.349523125 = 52.911 oz, and 13.50 ÷ 52.911 = $0.2551 per oz
Result: B is cheapest at $0.2341 per ounce. C is the most expensive at $0.2551.
Percent saved
Saved = (highest − lowest) ÷ highest × 100; More than cheapest = (price − lowest) ÷ lowest × 100
Worked example
The same three cereals, using unrounded unit prices of 0.249444, 0.234063 and 0.255146 per oz.
- 0.255146 − 0.234063 = 0.021083
- 0.021083 ÷ 0.255146 = 8.26% less for B than for C
- 0.021083 ÷ 0.234063 = 9.01% more for C than for B, and A is 6.57% more than B
Result: Buying B instead of C saves 8.26% per ounce. The same gap read from the cheaper side is 9.01%.
Multipacks and mixed units
Total = size of one × packages
Worked example
A 12-pack of 12 fl oz cans at $6.99, a 2 L bottle at $1.89 and a 1 gallon jug at $3.29. Compare per fl oz.
- 12-pack: 12 × 12 = 144 fl oz, and 6.99 ÷ 144 = $0.0485 per fl oz
- 2 L: 2,000 mL ÷ 29.5735295625 = 67.628 fl oz, and 1.89 ÷ 67.628 = $0.0279
- Gallon: 128 fl oz, and 3.29 ÷ 128 = $0.0257
- (0.0485 − 0.0257) ÷ 0.0485 = 47.05% less for the gallon than for the 12-pack, from unrounded figures
Result: The gallon jug is cheapest at $0.0257 per fl oz. The 12-pack holds the most and costs the most per ounce.
Conversion Factors Used
Each unit is stored as grams (weight), milliliters (volume) or single items (count). The pound and the gallon are exact definitions. The ounce, quart, pint and fluid ounce follow from them.
| Unit | Equals | How it is defined |
|---|---|---|
| 1 pound (lb) | 453.592 37 g | 0.453 592 37 kg exactly |
| 1 ounce (oz, weight) | 28.349 523 125 g | 1/16 of a pound |
| 1 kilogram (kg) | 1,000 g | Metric |
| 1 U.S. gallon (gal) | 3,785.411 784 mL | 231 cubic inches |
| 1 quart (qt) | 946.352 946 mL | 1/4 gallon |
| 1 pint (pt) | 473.176 473 mL | 1/8 gallon |
| 1 fluid ounce (fl oz) | 29.573 529 562 5 mL | 1/128 gallon |
| 1 liter (L) | 1,000 mL | Metric |
| 1 dozen | 12 items | Count |
Source: NIST Handbook 44 (2026), Appendix C — General Tables of Units of Measurement
Switching a Unit Price to Another Unit
If a label shows one unit and you want another, multiply by the number shown. The calculator does this for you when you change Compare price per.
| From | To | Multiply by |
|---|---|---|
| price per oz | price per lb | 16 |
| price per lb | price per oz | 1/16 (0.0625) |
| price per lb | price per kg | 2.2046 |
| price per oz | price per kg | 35.274 |
| price per fl oz | price per pint | 16 |
| price per fl oz | price per quart | 32 |
| price per fl oz | price per gallon | 128 |
| price per fl oz | price per liter | 33.814 |
Worked Example: Three Cereals per oz and per lb
Invented prices, computed with unrounded unit prices. The ranking and the percent saved do not change with the unit.
| Item | Total size | Per oz | Per lb |
|---|---|---|---|
| A: $4.49, 18 oz | 18 oz | $0.2494 | $3.99 |
| B: $7.49, 2 lb | 32 oz | $0.2341 | $3.745 |
| C: $13.50, 1.5 kg | 52.911 oz | $0.2551 | $4.08 |
How to Read Your Result
Two percentages for the same gap
Comparing $0.2551 with $0.2341 per ounce gives 8.26% less for the cheaper cereal, or 9.01% more for the pricier one. Both are correct and they use different baselines. This calculator reports the saving against the most expensive item, which answers how much you keep by choosing the cheapest.
Bigger is not always cheaper
Warehouse sizes and multipacks often cost less per unit, but not every time. In the soda example the 12-pack holds 144 fl oz and costs $0.0485 per fl oz, while a 2 L bottle with less than half as much costs $0.0279. A discount on the small size, a store brand or a sale can flip the usual order.
Why the unit you choose does not change the answer
Switching from price per ounce to price per pound multiplies every unit price by the same 16, so the cheapest item and the percent saved stay the same. Pick whichever unit you can picture. A label that rounds to the whole cent can hide a gap, though: $0.0485 and $0.0451 per fl oz both round to $0.05, which is why the table shows four decimals under a dollar.
Reading shelf labels
NIST’s model Uniform Unit Pricing Regulation, in Handbook 130, says a store that shows unit prices should use one unit for every size of the same product. Its example is soft drinks from 12 fl oz cans to 2 L bottles, priced all per fluid ounce, per quart or per liter. The model also rounds to the nearest cent at a dollar or more and to a tenth of a cent or a whole cent below a dollar, and exempts packages under 1 oz or 1 fl oz and items priced at 50 cents or less. Whether your state has adopted it varies.
Limitations & Accuracy Notes
- Unit price is the only thing compared. Quality, ingredients, freshness, coupons, loyalty prices, sales tax and whether you will finish a large package before it spoils are not in the number.
- Weight and volume are never converted into each other, because that needs the density of the specific product. Items entered in different kinds of unit are listed but not ranked.
- Liquid volume means U.S. units. An Imperial gallon is 4.546 09 L, about 20% larger than a U.S. gallon, so UK or Canadian package sizes in Imperial units need converting to liters or milliliters first. Dry pints and quarts, length and area units are not included.
- The size you type is used as given. A label that lists net weight for the food and a different weight with packaging, or a drained weight for canned goods, changes the answer, so enter the figure you are actually paying for.
- Prices are treated as dollars, but any currency works if every item uses the same one.
- The sample items shown when the page opens are made up. Replace them with your own prices before relying on a result.
Frequently Asked Questions
How do you calculate unit price?
Divide the price by the amount you get. $4.49 for 18 oz is 4.49 ÷ 18 = $0.2494 per ounce. When packages use different units, convert them to one unit first: 2 lb is 32 oz, so $7.49 for 2 lb is $0.2341 per ounce. The lower unit price is the better deal per unit.
How do I compare prices per ounce when sizes are in pounds, grams or kilograms?
Convert every size to the same unit. One pound is 16 oz or 453.59237 g, so 1.5 kg is 52.911 oz, and $13.50 for it is $0.2551 per ounce. This calculator converts for you, and the ranking comes out the same whichever unit you pick.
Is the bigger package always cheaper per unit?
No. A 12-pack of 12 fl oz cans at $6.99 holds 144 fl oz and costs $0.0485 per fl oz. A 2 L bottle at $1.89 holds 67.628 fl oz and costs $0.0279, so the smaller package is cheaper per ounce. Check the unit price of each size instead of assuming.
How do I calculate the unit price of a multipack?
Multiply the size of one package by the number of packages, then divide the price by that total. Six 12 fl oz cans hold 72 fl oz. Enter 12 in Size of each and 6 in Packages, and the calculator does the multiplication before it divides the price.
Can I compare ounces with fluid ounces?
No. An ounce of weight and a fluid ounce of volume measure different things, and converting one to the other needs the product’s density. If one item is sold by weight and another by volume, the calculator says they can’t be compared and shows each price in its own unit instead of ranking them.
How many fluid ounces are in a gallon, and how many ounces in a pound?
A U.S. gallon is 128 fluid ounces, 4 quarts or 8 pints, which is 3,785.411784 mL. A pound is 16 ounces, or 453.59237 g. Both come from NIST Handbook 44. To go from price per fl oz to price per gallon, multiply by 128. For price per ounce to price per pound, multiply by 16.
How do I work out the percent saved?
Subtract the lowest unit price from the highest, then divide by the highest. With $0.2551 and $0.2341 per ounce that is 8.26% less. Measured the other way, the pricier cereal costs 9.01% more than the cheaper one. It is the same gap with a different baseline, and the calculator reports the first.
Do stores have to show unit prices?
In many states it is voluntary. NIST’s model Uniform Unit Pricing Regulation (Handbook 130) says how a store should show unit prices when it provides them, and a 2017 NIST post counted 41 states where unit pricing was voluntary. State law differs and can change, so ask your state’s weights and measures office.
References & Further Reading
- NIST Handbook 44 (2026), Appendix C — General Tables of Units of Measurement — Exact pound and gallon definitions; 231 cubic inches; 128 fluid ounces, 8 pints and 4 quarts to the gallon
- NIST SP 811, Appendix B.9 — Factors for units listed by kind of quantity — Seven-digit values for the ounce, fluid ounce, pint, quart and gallon, which agree with the factors used here
- NIST Handbook 130 (2026), IV.C — Uniform Unit Pricing Regulation — Model rules for units, rounding, exemptions and consistent units across sizes
- NIST Taking Measure — The Unit Price is Right (March 2017) — Unit pricing voluntary in 41 states as of 2017