Unit Price Calculator — Compare Package Sizes

Unit Price Comparison

Enter each option’s price and size. Units just need to match each other — grams, ounces, sheets, litres, whatever the label says.

Option A price

Option A size

Option B price

Option B size

Option C price (optional)

Option C size

Option B is the better value

Compares only the figures you enter, so the units must match each other. It cannot know about multi-buy offers, loyalty pricing, or whether you will get through the larger quantity before it goes off — all three can beat the better unit price.

How unit pricing works

Divide the price by the quantity, and compare the results. That is the whole method:

$4.99 for 500 g → 4.99 ÷ 500 = $0.00998 per gram
$7.49 for 800 g → 7.49 ÷ 800 = $0.00936 per gram

The 800 g pack wins by about 6%. The awkward part is not the division — it is that you have to hold the first answer in your head while calculating the second, standing in an aisle, and the numbers are small enough that a mis-remembered digit flips the result.

Where the bigger size loses

Bulk is usually cheaper per unit, but not always, and there are three reliable exceptions:

Promotions on the small size. A 2-for-1 on the small pack routinely beats the family size.
Different units on the shelf label. Per 100 g next to per kilo, or per sheet next to per roll, hides real differences. Convert to one unit first.
Waste. A cheaper price per gram on a quantity you cannot finish is not a saving at all.

Mismatched units

If one label is in ounces and the other in grams, convert before comparing — the weight converter handles it, and volume covers fluid ounces, millilitres, and the US/UK gallon difference that trips up imported goods.

Doing this in a shop

This page needs a signal. A supermarket aisle frequently does not have one, which is precisely when you need the comparison. CalcBoard runs offline with two calculator panels side by side — one per product, both results visible at once, no memorising and no app switching. The free Price Comparison layout sets that up in a tap, and two panels are free forever.

It is also exact. Prices are decimal numbers, and CalcBoard adds them the way a till does rather than the way floating-point hardware does, so the totals reconcile to the cent.

Frequently Asked Questions

How do I compare prices of different sizes?

Divide each price by its quantity to get a price per unit, then compare those. $4.99 for 500 g is $0.00998/g; $7.49 for 800 g is $0.00936/g, so the larger pack is cheaper per gram.

Is the bigger package always cheaper per unit?

No. Promotions on smaller sizes, multi-buy offers, and premium packaging regularly make the small size cheaper per unit. It is worth checking rather than assuming.

What if the two labels use different units?

Convert one to the other first — ounces to grams, or fluid ounces to millilitres — then divide. Comparing a per-ounce figure with a per-gram figure gives a meaningless answer.

Can I do this without a data connection?

Not on this page, but the CalcBoard app runs entirely offline with two calculator panels side by side, which is the setup this comparison actually wants in a shop.

Compare in the aisle, offline

Two prices, two panels, both visible at once. Free, no ads, no connection needed.

Download Free on App Store