Unit Price Calculator
Compare two package prices after converting count, mass, or volume to one consistent unit.
Content updated August 4, 2026
Item A
Item B
Compare like products and the same net contents. Quality, waste, shipping, tax, deposits, promotions, and usable yield are not included.
Compare two package prices on the same quantity basis even when their labels use different units. Choose count, mass, or volume, enter each package's price and net quantity, then select the common unit in which both unit prices should be displayed.
The calculator converts quantities before dividing price by quantity. That prevents a 2-litre bottle from being compared directly with a 12-fluid-ounce package and makes the lower unit price, percentage difference, and equal-quantity cost visible.
The Unit Price formula
Unit price = package price ÷ package quantity expressed in the common comparison unitConverted quantity = entered quantity × input-unit base factor ÷ output-unit base factor · savings % = (higher unit price − lower unit price) ÷ higher unit price × 100.
Worked example
Item A costs 5 for 10 items, or 0.50 each. Item B costs 8 for 20 items, or 0.40 each. Item B has the lower unit price by 0.10 per item, which is 20% below Item A's 0.50 unit price.
Assumptions, rounding, and limitations
Assumptions
- Both products are sufficiently comparable and their entered quantities represent net contents.
- Prices use the same selected currency and include the same kinds of charges.
- Mass and volume conversions use the documented NIST factors; U.S. customary volume units are not Imperial units.
- The output unit belongs to the same count, mass, or volume dimension as both package quantities.
Rounding: Conversion and unit-price math retain floating-point precision. Displayed prices round to two currency decimals and percentage savings to two decimals.
Limitations
- Does not include tax, shipping, deposits, memberships, coupons, subscriptions, tier pricing, spoilage, concentration, quality, or usable yield.
- Cannot convert between count, mass, and volume without product-specific density or per-item information.
- Does not generate a legally compliant retail unit-price label or determine jurisdiction-specific pricing obligations.
Sources
- NIST SP 1181 Unit Pricing Guide, 2025 Edition — National Institute of Standards and Technology
- NIST Guide to the SI, Appendix B: Conversion Factors — National Institute of Standards and Technology
A common unit makes the comparison meaningful
NIST describes unit pricing as the cost per unit of measure and recommends consistent units across a product category, including when package labels use mixed units. This tool enforces that principle by rejecting comparisons across count, mass, and volume dimensions.
Mass supports grams, kilograms, ounces, and pounds. Volume supports millilitres, litres, and explicitly labeled U.S. fluid ounces, cups, pints, quarts, and gallons. Count uses whole or fractional entered quantities but does not assume what one item contains.
Unit price is one part of product value
The lower unit price is the cheaper amount for the same labeled net contents, not necessarily the better purchase. Product quality, waste, shelf life, concentration, shipping, tax, deposits, coupons, subscriptions, and usable yield can change the real choice.
NIST notes that unit-pricing laws and practices vary by jurisdiction. This consumer comparison does not create a shelf label or determine retailer compliance with local pricing or package-labeling requirements.
Frequently asked questions
▶How is unit price calculated?
Convert the package quantity to the chosen comparison unit, then divide the package price by that converted quantity.
▶Can I compare kilograms with pounds?
Yes. Both are mass units, so the calculator converts them to the same selected mass unit before comparing prices.
▶Can I compare litres with ounces?
Yes, when ounces means U.S. fluid ounces. Ordinary ounces are mass units and cannot be compared directly with volume.
▶Why can’t I compare count with weight?
A count does not reveal mass without product-specific information. The calculator rejects cross-dimension comparisons instead of inventing a conversion.
▶Does the lower unit price always mean better value?
No. It only compares labeled quantity and price. Quality, concentration, waste, promotions, tax, delivery, and how much you will use are outside the formula.
Related calculators
Work out the sale price and how much you save from a percentage discount.
Open calculator →Work out a percentage of a number, what percent one number is of another, and percentage increase or decrease.
Open calculator →Add sales tax or VAT to a price to see the tax amount and total you'll pay.
Open calculator →Disclaimer: Unit Price Calculator results are estimates for general information and education only, and are not financial, tax, legal or medical advice. Verify important decisions with a qualified professional.