UNIT PRICE CALCULATOR
$4.99 ÷ 12 oz = $0.4158 per oz. If the two units differ, Product B’s quantity is converted to Product A’s unit first, so both prices are compared per the same unit. Weight and volume never mix. This tool compares only the numbers you enter. It does not know product quality, coupons, taxes, loyalty pricing, or local store rules.
Updated June 2026 · Built by Lukáš, an architect in Prague.
Formula, assumptions, rounding & limitations
Formula
unit price = price ÷ quantity- If units differ:
quantity Bis converted to Product A’s unit first (Product A’s unit is the comparison unit). percent cheaper = (higher unit price − lower unit price) ÷ higher unit price × 100unit price change = (new unit price − old unit price) ÷ old unit price × 100size change = (new size − old size) ÷ old size × 100
Assumptions
- Exact conversion factors: 1 lb = 453.59237 g, 1 oz = 28.349523125 g, 1 fl oz = 29.5735295625 ml, 1 kg = 1000 g, 1 l = 1000 ml.
- Weight and volume are separate categories and are never converted into each other.
- Count-like units (count, sheet, roll, wash / load) only compare with the exact same unit.
- Prices are compared as entered — before tax, coupons, or loyalty discounts.
- Both decimal comma (4,99) and decimal point (4.99) are accepted; a leading $ is ignored.
Rounding
- Unit prices display with 2 decimal places by default. If two different unit prices would round to the same value, the display expands to 3–4 decimals so the difference stays visible.
- Percentage verdicts are always computed from full precision, not from the rounded display values.
- The line under the result shows the math at 4-decimal precision.
Limitations
- Cross-category comparisons (e.g. oz vs ml) are blocked — those units measure different things.
- Sales tax is not added — use the Sales Tax Calculator for the after-tax price.
- Coupons and promotions are not applied — compare discounted prices with the Discount Calculator first.
- Product quality, brand, and pack-size convenience are not part of the math.
What is a unit price?
The cost of one measurement unit of a product — one ounce, one pound, one liter, or one item. It is the price divided by the package quantity: a $4.99 pack of 12 oz costs $0.4158 per ounce. Comparing unit prices is the only reliable way to compare different package sizes.
How do I compare ounces and pounds?
Pick oz for one product and lb for the other — the calculator converts them automatically (1 lb = 16 oz = 453.59237 g) and shows both prices in the first product’s unit. Weight and volume can’t be mixed: ounces measure weight, fluid ounces measure volume.
Is a bigger package always cheaper per unit?
Usually, but not always — that’s why it’s worth checking. Promotions sometimes make the smaller pack cheaper per unit, and shrinkflation can quietly turn a “family size” into the worse deal. Only nine US states require stores to show unit prices on the shelf, so in most places you have to do this math yourself.
How do I calculate shrinkflation?
Switch to “Old vs new package” mode. Enter the old price and size and the new price and size. The calculator shows how much the package shrank and how much the price per unit really increased — even when the sticker price stayed the same.
Does this include sales tax or coupons?
No. It compares shelf prices per unit only. Compare discounted prices with the Discount Calculator and add tax with the Sales Tax Calculator.