Free big number calculator
Add and compute arbitrarily large integers without floating-point precision loss — enter any large numbers to see exact results, updated live, as you type.
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Uses JavaScript BigInt for arbitrary-precision integer addition.
Results are estimates. Consult a professional.
How the big number calculator works
Standard JavaScript numbers (64-bit IEEE 754 floating point) can only represent integers exactly up to 2^53 − 1 (9,007,199,254,740,991). Beyond that, numbers lose precision. This calculator uses JavaScript's built-in BigInt type, which handles integers of arbitrary size with exact arithmetic — no floating-point rounding, no precision loss, no matter how many digits.
Worked example: where floating point fails and BigInt succeeds
Adding 1 to the 16-digit number 9,999,999,999,999,999 should give 10,000,000,000,000,000. Standard JavaScript Number gives the wrong answer; BigInt gives the exact result.
Floating point vs. BigInt precision comparison
The table shows specific values where JavaScript Number loses precision versus the exact BigInt result. The divergence grows larger with each additional digit.
| Expression | Number result | BigInt result | Error |
|---|---|---|---|
| 2^53 − 1 | 9007199254740991 | 9007199254740991 | None (boundary) |
| 2^53 | 9007199254740992 | 9007199254740992 | None (even) |
| 2^53 + 1 | 9007199254740992 | 9007199254740993 | Off by 1 |
| 9999999999999998 + 1 | 10000000000000000 | 9999999999999999 | Off by 1 |
| 20! (factorial) | 2432902008176640256 | 2432902008176640000 | Off by 256 |
| 100! (factorial) | 9.33e+157 (approx) | exact 158-digit integer | Significant |
Source: IEEE 754 double-precision specification and ECMAScript BigInt. Numbers above 2^53 − 1 may not be representable exactly as floating-point values.
Tips for working with very large numbers
Knowing when to use BigInt versus regular numbers — and the trade-offs involved — helps you avoid silent precision errors in critical calculations.
- Always use BigInt for integer counts above 9 quadrillion — any integer beyond 2^53 − 1 (9,007,199,254,740,991) is potentially unsafe with standard Number arithmetic.
- BigInt does not support decimals — BigInt is for exact integers only; for very large or very precise decimal arithmetic, use a dedicated library such as decimal.js.
- Cryptographic keys require BigInt — RSA and elliptic curve keys involve 256–4096 bit numbers; floating point cannot represent them.
- Factorials and combinations grow fast — n! exceeds 2^53 at n = 19; use BigInt when computing permutations or combinations for large n.
- Mix carefully — you cannot mix BigInt and Number in arithmetic (e.g., 1n + 1 throws an error); convert explicitly with BigInt(x) or Number(bigint).
Accuracy and limitations
BigInt arithmetic is exact for integers of any magnitude — there is no fixed precision limit. However, extremely large numbers (thousands of digits) take longer to compute because the number of operations grows with digit count. BigInt does not support fractional values, irrational numbers, or floating-point operations; for those, standard Number or dedicated decimal libraries are appropriate. Division in BigInt truncates toward zero and discards any remainder, so 7n / 2n = 3n, not 3.5.
Key terms
About this calculator
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