Big Number Calculator
Perform exact arithmetic on integers far beyond the safe range of normal numbers using JavaScript BigInt.
Example
Multiply two 30-digit numbers exactly:
A = 123456789012345678901234567890
B = 987654321098765432109876543210
A × B = 121932631137021795226185032733622923332237463801111263526900
(60 digits, exact — no floating-point rounding)
How it works
Type two whole numbers of any size, pick an operation (+, −, ×, ^, mod), and the exact integer result is computed instantly with BigInt. Power and modulo are guarded against invalid inputs.
Good to know
The Big Number Calculator performs exact arithmetic on whole numbers that are far too large for an ordinary calculator or spreadsheet to handle accurately. You enter two integers (A and B), choose an operation — addition, subtraction, multiplication, A raised to the power of B, or A modulo B — and it returns the complete result using JavaScript's BigInt, which keeps every single digit instead of rounding. It is built for programmers checking cryptographic or hashing math, students working through combinatorics and number theory, and anyone who has ever seen a calculator collapse a long answer into "1.23e+30".
Reach for it whenever a value can exceed roughly 16 digits, the point where standard floating-point numbers (the IEEE 754 doubles behind most calculators and JavaScript) start silently dropping low-order digits. Typical cases include multiplying large factorials, computing huge powers, verifying modular results in RSA-style examples, or simply confirming the exact product of two long account or serial numbers. Because it runs entirely in your browser, nothing you type is sent to a server.
Read the result alongside the three stat boxes below it. "Digits" counts the significant digits of the answer (a leading minus sign and leading zeros are ignored), "Sign" tells you whether the value is Positive, Negative, or Zero, and "Even / Odd" reports parity from the final digit — a quick sanity check, since any product involving an even factor must be even. The full number is shown with word-break wrapping so even a 60-digit answer stays on screen.
A few practical limits to keep in mind:
- Inputs must be whole integers (an optional leading minus is allowed); decimals and fractions are not supported, and the tool strips spaces, commas, and underscores so you can paste grouped numbers.
- For A ^ B the exponent must be between 0 and 100000, modulo by zero is rejected, and modulo uses truncated (toward-zero) division, so the sign of A mod B follows A — which can differ from the always-positive remainder some math classes expect.
Frequently asked questions
Why use this instead of a normal calculator?
Regular JavaScript numbers lose precision above 9,007,199,254,740,991 (2^53−1). This tool uses BigInt, so every digit of huge integers is computed exactly with no rounding.
Does it handle decimals or fractions?
No. BigInt is integer-only, so inputs must be whole numbers. A modulo result follows BigInt's truncated division (the sign of the result matches A), and the power operation requires a non-negative integer exponent.
Is my data uploaded anywhere?
No — this calculator runs entirely in your browser; nothing is uploaded.
Is it free?
Yes, completely free with no sign-up and no limits.
People also ask
What is the largest number a regular calculator can handle accurately?
Most calculators and JavaScript use 64-bit floating-point numbers, which stay exact only up to 9,007,199,254,740,991 (2^53 minus 1), about 16 digits. Beyond that, low-order digits are rounded, so a BigInt-based tool is needed for exact results.
What is BigInt and why does it give exact results?
BigInt is a numeric type that stores integers of arbitrary length instead of squeezing them into a fixed 64-bit slot. Because it never converts to floating point, every digit of an addition, multiplication, or power is preserved exactly with no rounding.
How do I multiply two very large numbers without losing precision?
Enter both whole numbers, select the multiply (A x B) operation, and the exact product is computed digit-for-digit using BigInt. Unlike a spreadsheet, it will not switch to scientific notation or truncate the trailing digits.
Why does the modulo result sometimes come out negative?
This tool uses truncated (toward-zero) division, matching the behavior of the % operator, so the result takes the sign of A. For example, -7 mod 3 returns -1 rather than the positive 2 produced by mathematical floored modulo.
Can I calculate large exponents or factorials with it?
You can compute A raised to a non-negative integer exponent up to 100000 directly. Factorials are not a built-in operation, but you can build up large products step by step using the multiply operation.
Does this calculator work with negative numbers?
Yes for addition, subtraction, multiplication, and modulo, where a single leading minus sign is allowed. The power operation, however, requires the exponent B to be zero or positive, since negative exponents would produce fractions that integers cannot represent.
Is there a limit to how many digits I can enter?
There is no fixed digit cap on the two input integers themselves; they are limited only by your browser's memory. The one explicit restriction is the exponent for the power operation, which is capped at 100000 to keep results manageable.
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