Math · Rates
Unit price comparison calculator.
Enter the price and quantity for up to three items and see the price per unit, which one is the best buy and by how much the others cost more.
Inputs
Best buy
Enter a price and a quantity for at least two items.
How to compare unit prices
The unit price is the cost of one unit: divide the price by the quantity. Comparing unit prices can show which size is the best buy. It does not tell you anything about quality, only about cost per unit.
Worked example. Which is better, 2 litres of milk at $3.80 or 1.5 litres at $2.70? $3.80 ÷ 2 = $1.9 per litre and $2.70 ÷ 1.5 = $1.8 per litre, so the 1.5 litre carton is the lower unit price. The 2 litre carton costs 5.6% more per litre.
Counting items. 10 pencils for $4.00 or 6 pencils for $2.70? $4.00 ÷ 10 = $0.4 each and $2.70 ÷ 6 = $0.45 each, so 10 pencils for $4.00 wins.
Put the price on top when you divide, because you want the price for one unit.
Frequently asked questions
How do you calculate unit price?
Divide the price by the quantity. 2 litres for $3.80 is $3.80 ÷ 2 = $1.90 per litre.
How do I compare two sizes to find the best buy?
Work out the unit price of each and pick the lowest. $3.80 for 2 L is $1.9 per litre and $2.70 for 1.5 L is $1.8 per litre, so the smaller one is cheaper per litre.
Does the lowest unit price always mean the best deal?
Not always. It only compares cost per unit, not quality, whether you will use it all before it spoils, or whether you have space to store it.
What if the items use different units?
Convert them to the same unit first (all in grams, or all in millilitres). This tool compares the numbers you enter without converting.
What does the percent more column mean?
It is how much higher an item's unit price is than the lowest one, measured against the lowest price.
Sources
Checked
Runs entirely in your browser. Nothing you type is sent or stored.
For learning
Prices can be in any currency. Compare like with like. Results are rounded for display. Check with your teacher's required method when you hand in homework.