Unit Price Calculator

Is the big pack really cheaper? Enter each option’s price and size — in grams, ounces, pounds, litres, fluid ounces or items, and even as multipacks — and the calculator converts them to the same unit price, ranks them from best value to worst and shows how much you save per unit and on the amount you need.

What unit price means

The unit price is the cost per standard amount — per ounce, per 100 grams, per litre or per item. It lets you compare packs of different sizes fairly. A 340 g jar at $3.49 costs about $1.03 per 100 g, while a 1 kg jar at $6.29 costs about $0.63 per 100 g — so the bigger jar is almost 40% cheaper per gram, even though it costs more at the till.

The formula

Unit conversions used

Weight ounces and fluid ounces measure different things: compare weight with weight and volume with volume. The calculator only compares options of the same kind.

How to use the calculator

1. List each option on its own line: name | price | quantity | unit, adding a pack count for multipacks.
2. Read the ranking — the best value is highlighted and others show how much more they cost per unit.
3. Enter how much you actually need to see the cost and your saving on that amount.
4. Change prices to check whether a sale or coupon changes the winner.

Worked example

Comparing peanut butter: a 340 g jar at $3.49, a 1 kg jar at $6.29, a twin pack of 12 oz jars at $5.99 and a 5 lb warehouse tub at $13.49. Converted to price per 100 g, the tub is about $0.59, the 1 kg jar $0.63, the twin pack $0.88 and the small jar $1.03. The tub is the best value per gram — but only if you will use 2.27 kg before it goes stale.

When the cheapest unit price isn’t the best buy

• You won’t use it before it spoils or expires.
• You don’t have room to store it.
• The larger pack ties up money you need elsewhere.
• Quality or brand differs — compare like with like.
• A coupon or loyalty discount applies only to the smaller size.

Everyday comparisons

For products like toilet paper and detergent, the useful unit is a sheet or a wash, because packs describe “mega rolls” and concentrates in different ways.

Multipacks and bulk buys

Multipacks are usually but not always cheaper per unit. Supermarkets sometimes price single items on promotion below the multipack rate, and warehouse clubs may charge more per unit for some brands. Always convert to the same unit. If you buy in bulk, check use-by dates and whether you have space to store the extra — waste cancels the saving.

Shrinkflation

When package sizes shrink while prices stay the same, the unit price rises even though the shelf price hasn’t changed. Comparing unit prices over time — for example in the price book workbook in the printable pack — reveals these hidden increases and helps you switch to better-value alternatives.

Store brands vs name brands

Store-brand products are often made to similar specifications and can be 20–40% cheaper per unit. Compare unit prices across brands as well as sizes, and try the store brand for staples such as flour, sugar, rice and cleaning products, where differences are small. For items where you care about taste or performance, a small premium may be worth paying — the calculator shows exactly how big that premium is.

Using the calculator in the shop

1. Open the page on your phone before shopping.
2. Type each option as you compare shelves.
3. Check that you’re comparing the same quality and brand level.
4. Use the “how much do you need” box for recipes or bulk buys.
5. Note the winner in your shopping list for next time.

Shelf labels

Many supermarkets print unit prices on shelf labels, but they sometimes use different units for different products (per 100 g on one, per kg on another) or per-item pricing on multipacks. Converting everything to the same unit, as the calculator does, avoids being misled.

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