Two jars of the same sauce sit on the shelf. One is bigger and costs more, the other is small and cheap. Which is the better deal? You cannot tell from the sticker price alone, because the sizes are different. The answer is the unit price: what each one costs for a single, standard amount.
TL;DR — Enter each product’s price and size in the unit price calculator and it flags the lowest cost per unit for you.
What a unit price is
A unit price is the cost of one standard amount of a product, such as per kilogram, per litre or per item. Once every option is expressed the same way, comparing them is just reading off the smallest number.
Most shops are required to print a unit price on the shelf label, usually in small text under the main price. It is there for exactly this reason, though it is easy to miss and shops do not always use the same base amount from one product to the next.
How to work it out
Divide the price by the size:
- A $6.00 pack holding 1 kg is $6.00 ÷ 1 = $6.00 per kg.
- A $3.50 pack holding 400 g is $3.50 ÷ 0.4 = $8.75 per kg.
The smaller pack looks cheaper at the till, but it costs nearly $3 more per kilogram. The bigger pack is the better value here.
The big pack is not always cheaper
Buying big usually lowers the unit price, but not always. A multi-buy offer can push a smaller pack below the family size, and “value” packs are sometimes priced up on the assumption that nobody checks. The only way to know is to compare the cost per unit every time.
Mixing units
Products often come in different units, one in grams and another in kilograms, or ounces against pounds. To compare them you have to convert everything to the same unit first. The unit price calculator does that step for you: pick the measure, set each item to its own unit, and it normalises them before ranking.
Then check the final price
Unit price tells you the better value, but your budget cares about the total. Once you have picked a product, use the discount calculator for any sale price and the sales tax calculator for the checkout total.
