Big number calculator
Exact arithmetic on very large numbers: add, subtract, multiply, divide, powers and factorials.
About this calculator
This big number calculator works with numbers far too large for an ordinary calculator, and keeps every digit exact.
It adds, subtracts, multiplies and divides, and works out powers, factorials, remainders and square roots to as many decimal places as you choose.
How it works
The numbers are stored as exact whole numbers plus the position of the decimal point, so every digit is kept. Division and square roots stop at the number of decimal places you choose.
Last reviewed:
Worked example
- First number: 123456789012345678901234567890
- Operation: ×
- Second number: 987654321098765432109876543210
Result: 1.219326 × 10^59
Common questions
Why do ordinary calculators lose digits?
They store about 15 to 16 significant digits, so large results are rounded. This calculator keeps every digit.
How many digits does 100! have?
158 digits. Factorials grow so fast that 1,000! has 2,568 digits.
Can it handle decimals?
Yes. Addition, subtraction and multiplication are exact, and division and square roots go to as many decimal places as you choose.
Sources and further reading
The story behind it
Where the idea came from: In 1949, the ENIAC computer worked out π to 2,037 decimal places, one of the first big-number calculations done by machine.
Exact arithmetic on huge whole numbers now protects online banking and messaging: the keys used for encryption are numbers hundreds of digits long.
Why you can trust this calculator
- It runs in your browser. Nothing you type into it is sent anywhere.
- The method is explained on this page, so you can check it yourself.
- Free to use, with no sign-up.
- Results are estimates, so please double-check anything important.
- Spotted a mistake? Tell us and we'll look into it.
After 15 years as a mathematics educator, I built CalculStore to give students, teachers, professionals and anyone working with numbers simple, reliable tools.
Meet the founder