How do you calculate a unit rate?

Divide the total by the quantity. $12.00 for 3 items is $12.00 divided by 3, which is $4.00 per item, and $15.00 for 5 items is $3.00 per item. The quantity does not have to be a whole number: 1.5 litres for $4.50 is $3.00 per litre, because 4.50 divided by 1.5 is 3, and the same offer the other way up is 0.333333 litre per $. The page shows the division it did, the answer with your unit attached, and the reciprocal, so you can check the step rather than trust a single figure.

Which way round should the rate go?

That depends on the question, which is why both directions are printed. Amount divided by quantity gives the cost of one: $12.00 for 3 items is $4.00 per item. Quantity divided by amount gives how many you get for one unit of the amount: the same offer is 0.25 item per $. Neither is more correct. For 120 km driven in 2 hours the first direction is the familiar one, 60 km per hour, while the second, 0.016667 hour per km, is the pace, and a runner wants that one. Read the label on each figure and take the one that answers your question.

How do I work out which of two packs is cheaper?

Enter the first pack at the top, the second in the offer below it, and give both the same unit. A 12 oz bottle at $3.29 is $0.274167 / oz and a 20 oz bottle at $5.49 is $0.2745 / oz, so the small one is lower, by 0.12%: close enough that the larger bottle is not the saving it looks like. The percentage is the gap between the two rates as a share of the higher one. The page names which offer is lower and by how much, and leaves the decision to you, since it knows nothing about how much of it you will use.

Why will it not compare a price per litre with a price per bottle?

Because they are not two prices for the same thing, and picking one would answer a question nobody asked. A comparison appears only when both offers carry the same unit, and when they do not the page says which two units it was given and stops there. Case and a trailing plural are not treated as a difference, so items and item count as the same unit, and so do Litre and litre. Different amount units are refused for the same reason: this page holds no exchange rates, so two currencies are never quietly treated as one.

Is the division exact?

Where a decimal can hold it in twelve places, yes, to the last digit: the arithmetic runs on whole numbers rather than floating point, so 5.49 divided by 750 is exactly $0.00732 per ml and not a figure with a tail on the end. Where the quotient does not end, or runs past twelve places, it is rounded once, to six decimal places, and the page names the figure it rounded. $10.00 for 3 items is $3.333333 per item, and the note under the answer says so rather than letting six decimals stand in for an answer that has no end.

Does anything I type leave my browser?

No. The division happens in the page, there is no account, no upload and no request to any server, and no price or exchange rate is fetched: every number in the answer comes from the numbers in the fields. Your last entries are kept in this browser so the page opens where you left it, and the Start over button on this page forgets them.

Unit Rate Calculator

Type a total, a quantity and the names of the units, and this page divides one by the other: $12.00 for 3 items opens as $4.00 per item, with the reciprocal, 0.25 item per $, printed next to it. Which of those two a person actually wants is the thing that trips people up, so both are on the screen at once and both carry the labels you typed rather than labels this page picked. The second offer is open beside it, and $15.00 for 5 items comes out at $3.00 per item, 25% less, and that comparison appears only because both offers are per item: a price per litre against a price per bottle is refused with a reason instead of being settled by a guess. The division itself runs in whole-number arithmetic rather than floating point, so a quotient that ends inside twelve decimal places is printed to its last digit, and anything longer is rounded once, to six, and named.

Unit rate$4.00 per item$12.00 ÷ 3 = $4.00 per item · reciprocal 0.25 item per $

Total

Quantity

Unit rate

$4.00 / item

Reciprocal

0.25 item / $

The unit rate is the amount for one unit. The reciprocal is how many units go with one of the amount, which is the same division the other way up. Both are printed, with the labels you typed, because which of the two you want depends on the question you are asking.

Compare a second offer

Total

Quantity

Unit rate

$3.00 / item

Reciprocal

0.333333 item / $

$12.00 ÷ 3per item
$4.00 / item
$15.00 ÷ 5per item
$3.00 / item
The two comparedboth per item
The second offer is lower: $3.00 / item against $4.00 / item, 25% less.

0.333333 item / $ is rounded to 6 decimal places, because the exact quotient needs more.

Accuracy. Exact division of the amount by the quantity, with the unit labels you typed carried through to the answer so the rate reads as a rate. A comparison appears only when both offers carry the same unit, because a price per litre and a price per bottle are not comparable and the page will say so rather than pick one. It uses the numbers you type and fetches no prices or exchange rates. A quotient that ends inside twelve decimal places is printed in full; anything longer is rounded once, to six, and the page names the figure it rounded rather than letting six decimals pass as the whole answer.

Common questions

How do you calculate a unit rate?: Divide the total by the quantity. $12.00 for 3 items is $12.00 divided by 3, which is $4.00 per item, and $15.00 for 5 items is $3.00 per item. The quantity does not have to be a whole number: 1.5 litres for $4.50 is $3.00 per litre, because 4.50 divided by 1.5 is 3, and the same offer the other way up is 0.333333 litre per $. The page shows the division it did, the answer with your unit attached, and the reciprocal, so you can check the step rather than trust a single figure.
Which way round should the rate go?: That depends on the question, which is why both directions are printed. Amount divided by quantity gives the cost of one: $12.00 for 3 items is $4.00 per item. Quantity divided by amount gives how many you get for one unit of the amount: the same offer is 0.25 item per $. Neither is more correct. For 120 km driven in 2 hours the first direction is the familiar one, 60 km per hour, while the second, 0.016667 hour per km, is the pace, and a runner wants that one. Read the label on each figure and take the one that answers your question.
How do I work out which of two packs is cheaper?: Enter the first pack at the top, the second in the offer below it, and give both the same unit. A 12 oz bottle at $3.29 is $0.274167 / oz and a 20 oz bottle at $5.49 is $0.2745 / oz, so the small one is lower, by 0.12%: close enough that the larger bottle is not the saving it looks like. The percentage is the gap between the two rates as a share of the higher one. The page names which offer is lower and by how much, and leaves the decision to you, since it knows nothing about how much of it you will use.
Why will it not compare a price per litre with a price per bottle?: Because they are not two prices for the same thing, and picking one would answer a question nobody asked. A comparison appears only when both offers carry the same unit, and when they do not the page says which two units it was given and stops there. Case and a trailing plural are not treated as a difference, so items and item count as the same unit, and so do Litre and litre. Different amount units are refused for the same reason: this page holds no exchange rates, so two currencies are never quietly treated as one.
Is the division exact?: Where a decimal can hold it in twelve places, yes, to the last digit: the arithmetic runs on whole numbers rather than floating point, so 5.49 divided by 750 is exactly $0.00732 per ml and not a figure with a tail on the end. Where the quotient does not end, or runs past twelve places, it is rounded once, to six decimal places, and the page names the figure it rounded. $10.00 for 3 items is $3.333333 per item, and the note under the answer says so rather than letting six decimals stand in for an answer that has no end.
Does anything I type leave my browser?: No. The division happens in the page, there is no account, no upload and no request to any server, and no price or exchange rate is fetched: every number in the answer comes from the numbers in the fields. Your last entries are kept in this browser so the page opens where you left it, and the Start over button on this page forgets them.

Exact division of the amount by the quantity, with the unit labels you typed carried through to the answer so the rate reads as a rate. A comparison appears only when both offers carry the same unit, because a price per litre and a price per bottle are not comparable and the page will say so rather than pick one. It uses the numbers you type and fetches no prices or exchange rates.