The term "mental arithmetic" refers to arithmetic performed mentally, in contrast to arithmetic performed with pencil and paper or with a calculator or other device. There are many advantages to being able to perform arithmetic mentally. For one, performing everyday calculations mentally is often faster than working a problem on paper or typing digits into a calculator. As well, there are many situations where a calculator may not be available. Finally, being able to perform calculations mentally can help to develop number sense.

If you want to improve your skill at mental arithmetic, there are several things you can try:

- It is essential to know the basics, such as the multiplication table up to 9×9. Being familiar with other things (e.g. the squares of small numbers) can also help.
- There are many techniques that can make mental calculation easier. Several of these can be found at the Calculation Shortcuts page.
- It is also useful to use estimation to get a rough idea of what the answer should be and to check that your answer is in the right ballpark. In everyday life, it isn't necessary to get the exact answer; one that's close is often good enough, and estimating the answer can often save calculation.
- As with everything, practice makes perfect. When you have a calculation to perform, try to perform it in your head instead of on your calculator.

There are also many books available that aim to teach the reader mental arithmetic.