Unit Price Calculator — Compare Cost Per Oz, Liter & More

Compare 2-4 products of different sizes to find the true cost per ounce, pound, gram, liter, gallon, or item — and see which one is the best value.

July 8, 2026

91% found this helpful

Reference Values

Last verified: Jul 8, 2026

Category	Range	What It Means	Status
NIST Handbook 130 — Uniform Unit Pricing Regulation	Model regulation, not a universal federal mandate	NIST publishes Handbook 130 as a model law that individual states and cities can voluntarily adopt. It standardizes how unit prices are calculated and posted, but it only has legal force where a state or local government has actually enacted it — there is no single US federal law requiring every retailer to post unit prices.	Good
States/cities with mandatory unit pricing	Varies — includes CA, NY, MA, and others	Some states (e.g. California, New York, Massachusetts) and cities require large grocery retailers to post shelf unit prices by local statute, often modeled on NIST Handbook 130's methodology. Coverage, store-size thresholds, and enforcement vary by jurisdiction — always confirm the posted unit price against your own math when it matters.	Okay
Weight comparison unit (US) ★	price per oz or price per lb	Most common comparison unit for packaged foods, snacks, and household goods sold by US customary weight.	★ Best
Metric weight comparison unit ★	price per 100 g or price per kg	Common on imported goods and increasingly on US shelf tags for items labeled in grams — price per 100g is the standard European/Handbook 130 convention for smaller items.	★ Best
Volume comparison unit (US) ★	price per fl oz, price per quart, or price per gallon	Standard for beverages, cleaning liquids, and other products sold by US customary volume.	★ Best
Metric volume comparison unit	price per 100 mL or price per liter	Common for imported liquids and increasingly for cosmetics/personal care items labeled in milliliters.	Good
Count-based comparison unit	price per count / price per each	Used for items sold as discrete units — paper towel rolls, diapers, batteries, capsules — where weight or volume isn't the meaningful comparison.	Good
Area comparison unit	price per sq ft	Used for flooring, tile, fabric, and other materials sold by area rather than weight or count.	Okay
Weight conversion: pounds to ounces	1 lb = 16 oz	Used to normalize weight-based prices entered in pounds to a common price-per-ounce basis.	Good
Weight conversion: kilograms to grams	1 kg = 1,000 g	Used to normalize metric weight-based prices entered in kilograms to a common price-per-gram basis.	Good
Weight conversion: ounces to grams	1 oz ≈ 28.3495 g	US customary avoirdupois ounce to metric gram, used to compare products where one is labeled in oz/lb and the other in g/kg.	Good
Volume conversion: gallons to fluid ounces	1 gal = 128 fl oz	Used to normalize volume-based prices entered in gallons to a common price-per-fluid-ounce basis.	Good
Volume conversion: quarts to fluid ounces	1 qt = 32 fl oz	Used to normalize volume-based prices entered in quarts to a common price-per-fluid-ounce basis.	Good
Volume conversion: liters to milliliters	1 L = 1,000 mL	Used to normalize metric volume-based prices entered in liters to a common price-per-milliliter basis.	Good
Volume conversion: fluid ounces to milliliters	1 fl oz ≈ 29.5735 mL	US customary fluid ounce to metric milliliter, used to compare products where one is labeled in fl oz/gal/qt and the other in mL/L.	Good

Source: NIST Handbook 130 (Uniform Unit Pricing Regulation, National Institute of Standards and Technology) for unit pricing methodology and adoption status; standard US customary/metric conversion constants (avoirdupois ounce, US fluid ounce) per NIST Handbook 44 Appendix C.

Worked Examples

Cereal: Two Box Sizes (Same Unit)

Brand A: $4.99 for 18 oz
Brand B: $6.49 for 24 oz

Brand B wins at $0.2704/oz vs $0.2772/oz

Brand A: $4.99 ÷ 18 oz = $0.2772/oz. Brand B: $6.49 ÷ 24 oz = $0.2704/oz. The bigger box costs more up front but is actually the better per-ounce value.

Laundry Detergent: Gallon vs Quart

Bottle A: $12.99 for 1 gal
Bottle B: $8.99 for 2 qt

Bottle A wins at $3.43/L vs $4.75/L

Bottle A: 1 gal = 3.78541 L, so $12.99 ÷ 3.78541 L = $3.43/L. Bottle B: 2 qt = 1.89271 L, so $8.99 ÷ 1.89271 L = $4.75/L. Converting gallons and quarts to a common liter basis shows the larger bottle is actually the better value.

Peanut Butter: Metric Weight (g vs kg)

Jar A: $5.49 for 500 g
Jar B: $9.99 for 1 kg

Jar B wins at $0.283/oz vs $0.311/oz

Jar A: 500 g × 0.035274 oz/g = 17.637 oz, so $5.49 ÷ 17.637 oz = $0.3112/oz. Jar B: 1 kg = 1,000 g = 35.274 oz, so $9.99 ÷ 35.274 oz = $0.2833/oz. Converting both to ounces (the tool's common weight unit) makes a 500g jar directly comparable to a 1kg jar.

Paper Towels: Count-Based Comparison

Pack A: $7.99 for 6 rolls
Pack B: $12.99 for 12 rolls

Pack B wins at $1.08/roll vs $1.33/roll

Pack A: $7.99 ÷ 6 rolls = $1.332/roll. Pack B: $12.99 ÷ 12 rolls = $1.0825/roll. For count-based goods, divide price by number of items rather than weight or volume.

Rice: Cross-Unit Comparison (lb vs oz)

Bag A: $8.99 for 5 lb
Bag B: $3.49 for 32 oz

Bag B wins at $0.1091/oz vs $0.1124/oz

Bag A: 5 lb = 80 oz, so $8.99 ÷ 80 oz = $0.1124/oz. Bag B: $3.49 ÷ 32 oz = $0.1091/oz. Converting Bag A's pounds to ounces first is what makes a fair comparison possible — comparing $8.99/5 against $3.49/32 directly would be meaningless.

How to Use This Calculator

1

Enter each product's price

Type the price you'd pay for each product exactly as shown on the shelf tag or receipt.
2

Enter the package size and unit

Enter how much is in the package (weight, volume, count, or area) and choose its unit from the dropdown — oz, lb, g, kg, mL, L, gal, qt, count, or sq ft.
3

Add up to 4 products

Use "Add another product" to compare more than two options at once — useful for store-brand vs. name-brand vs. bulk-size comparisons.
4

Read the Best Value badge

The calculator normalizes prices within each measurement type and marks the product with the lowest true unit price.

What Each Value Means

Unit Price ($ per unit): The cost of one single unit of a product — one ounce, one pound, one liter, one gallon, or one item — calculated as total price divided by quantity. This is the number that lets you compare products of different sizes fairly.
Normalized Comparison Unit (oz or L): The common base unit this calculator converts every entry to within a measurement type, so different package sizes and units can be ranked against each other: price-per-ounce for weight entries (oz/lb/g/kg) and price-per-liter for volume entries (mL/L/gal/qt).

Frequently Asked Questions

What is the unit price formula?

Unit price = Total price ÷ Quantity. You divide what you paid by how much you got, in a common unit (ounces, pounds, grams, liters, gallons, or individual items). This gives you the cost per single unit, so you can compare a small package against a large one on equal footing instead of comparing sticker prices alone.

Why is unit pricing more accurate than comparing total prices?

Total price tells you what you'll pay today, but it ignores package size — a $9.99 jar isn't automatically worse than a $5.49 jar if it holds twice as much. Unit price strips out the package size difference and shows the actual cost per ounce, gram, or liter, which is the number that actually determines whether you're getting a good deal.

Are stores required to post unit prices?

Not universally. NIST Handbook 130 (the Uniform Unit Pricing Regulation) is a model law that individual US states and cities can choose to adopt — it is not a single nationwide federal mandate. Some states, including California, New York, and Massachusetts, do require unit pricing on shelf tags for larger grocery retailers, but coverage and enforcement vary by jurisdiction. Where it isn't required, or where a shelf tag is wrong or missing, calculating it yourself is the only reliable way to compare.

How do I compare products listed in different units, like ounces and grams?

Convert both to the same base unit before comparing. This calculator does that automatically within a measurement type — weight-based entries (oz, lb, g, kg) are all converted to price-per-ounce, and volume-based entries (mL, L, gal, qt) are all converted to price-per-liter, so a 500g jar and a 1kg jar (or a quart bottle and a liter bottle) land on the same scale and can be ranked directly.

Can unit price comparisons be misleading?

Yes, in a few specific ways. Unit price only measures cost per amount — it says nothing about product quality, concentration (a "2x concentrated" detergent may need less per use), or whether you'll actually use the larger size before it expires or spoils. A slightly higher unit price on a smaller package can still be the smarter buy if the bulk size would go to waste.