Unit Price Calculator — compare package sizes

How it works

The calculation is a single division — price ÷ quantity — but its value is the comparison. Enter up to three packages in whatever unit they share (ounces, loads, count, sheets) and the table lists each one's unit price and marks the lowest as the better buy. It's the number grocery shelf tags print in small type, and the one that cuts through "bigger box, bigger price" to show which size actually costs less per use. Keep the units consistent across packages — compare price per ounce to price per ounce, not per ounce to per pound.

Worked example

The anchor is OpenStax's detergent comparison: liquid at $14.99 for 64 loads is $14.99 ÷ 64 ≈ $0.23 per load, while powder at $15.99 for 80 loads is $15.99 ÷ 80 ≈ $0.20 per load. The powder costs more on the shelf but less per load, so it is the better buy — exactly OpenStax's conclusion that "the better buy is the item with the lower unit price." A third slot lets you weigh a smaller store-brand pack against both; the unit prices are this calculator's own division of your figures.

Frequently asked questions

How do I calculate unit price?

Divide the package price by its quantity: $3.99 for 24 bottles is $3.99 ÷ 24 ≈ $0.17 per bottle. Do the same for each package and compare the results — the lowest price per unit is the cheapest per use, regardless of the sticker price.

Why isn't the biggest package always the cheapest per unit?

Usually it is, but not always — stores sometimes price a mid-size or promotional pack lower per unit than the giant one. That's the whole reason to compute unit price rather than assume: this page found the 40-load pack at $9.49 costs $0.24 per load, dearer than the 80-load box at $0.20, even though it's the smaller, cheaper-looking option.

What units should I use?

Whatever the packages share — ounces, grams, loads, sheets, count — as long as you use the same unit for every package. Comparing price per ounce to price per pound gives a meaningless ranking. If two items are measured differently, convert one first so both quantities are in the same unit.

Does the lower unit price always mean I should buy it?

It's the cheaper option per unit, which is what this page tells you. Whether it's the right buy also depends on whether you'll use it before it expires, storage space, and the upfront cost — a warehouse-size unit price is only a saving if the product doesn't go to waste. The math finds the cheaper rate; the decision is yours.

How does the better-buy highlight work?

The table computes each package's unit price and highlights the lowest one. It compares the exact quotients, not the rounded cents shown, so it picks the true minimum even when two options round to the same displayed price. Packages with a quantity of zero are left out.

Can I compare just two packages?

Yes — fill in two and leave the third quantity at zero, and it drops out of the comparison. The highlight then picks the cheaper of the two. There's nothing special about three; it's just the most sizes you'll usually weigh at once on a shelf.

How accurate is this, and what does it exclude?

The division is exact for the prices and quantities entered; displayed unit prices are rounded to the cent (OpenStax's convention), while the highlight uses the exact values. It excludes taxes, deposits, coupons, and loyalty discounts, and it assumes the quantities are in the same unit — convert first if they aren't.