Multiplication Calculator

What this calculator does

You have a whole string of numbers to multiply together, not just two, and doing it one pair at a time is fiddly and easy to fumble. This takes the lot in one go.

Paste your numbers in and it gives you how many there were and their product, the result of multiplying all of them. It runs right here in the browser, nothing to install.

Using the calculator

1. Enter your numbers, separated by commas, spaces, or line breaks: 1.618, 2, 3.14, -8.5.
2. Press Calculate.

You get back the count of numbers and their product. Reset clears the box.

The product, and a couple of handy rules

The answer to a multiplication is called the product. Multiplying is really just scaling: 6 × 4 is six lots of four, or four lots of six, which come to the same 24 either way. That is the first handy rule: order does not matter. You can multiply your numbers in any order and get the same product, so the tool can run straight through the list.

The second rule is about minus signs. Each negative number in the list flips the sign of the running answer. So the trick is just to count the negatives: an even number of them cancel out and the product is positive, an odd number leaves it negative. Two negatives make a positive, three make a negative, and so on.

One more thing worth knowing: if any number in your list is zero, the whole product is zero, no matter what else is in there. A single zero wipes everything out.

A worked example

Take 2.5, 4 and -3.

1. Multiply the first two: 2.5 × 4 = 10.
2. Bring in the third: 10 × -3 = -30.

The product is -30. There was one negative in the list, an odd number of them, so the answer came out negative, exactly as the sign rule predicts. Had there been a second negative, it would have flipped back to positive 30.

Units and precision

If your numbers carry units, remember that multiplying multiplies the units too. Two lengths in metres multiplied together give an area in square metres, not metres. It is a small thing that trips people up, so keep an eye on what the answer is actually measuring.

On precision, the calculation runs in the browser's standard maths and the product is shown to a good many decimal places. As with any calculation, the answer is only as exact as the numbers you put in, so round it back to match your data when you are done.

Questions people ask

Can I multiply more than two numbers at once?

Yes, that is the point of it. Enter as many as you like, separated by commas or spaces, and it multiplies them all together.

What happens with negative numbers?

Count the negatives. An even number of them gives a positive product, an odd number gives a negative one. Two negatives make a positive.

Does the order of the numbers change the answer?

No. Multiplication gives the same product whatever order you multiply in, so you can enter your numbers however you like.

What if one of my numbers is zero?

The product is zero. A single zero anywhere in the list makes the whole result zero.

Does it handle decimals?

Yes. Decimals and negatives are both fine, in any mix.

References

A note on where this comes from. Multiplication is commutative and associative, meaning the numbers can be multiplied in any order and any grouping for the same product, which is what lets a list be worked through in one pass. For further reading, see Multiplication.

1. The commutative and associative properties of multiplication, which make the product of a set of numbers independent of their order.
2. The sign rule for products, that the result is negative when there is an odd number of negative factors and positive otherwise.