Big Number / Arbitrary Precision Calculator

JavaScript's native number type loses precision for integers larger than 2⁵³ (about 9 × 10¹⁵). Anything cryptographic (RSA keys, hashes interpreted as integers), combinatorial (large factorials, binomial coefficients), or scientific (Avogadro × moles for very large mole counts) needs arbitrary precision. BigInt gives you exact integer arithmetic with no upper limit other than memory.

A JavaScript primitive type added in ES2020 for exact integer arithmetic of any size. Created with literal suffix (1234n) or BigInt(value) constructor. Operations between BigInt and regular Number throw a TypeError, so the two types don't accidentally mix. This calculator uses BigInt under the hood.

No — BigInt only handles integers. For exact decimal arithmetic (financial calculations, scientific measurements with fractional precision), you need a different library: decimal.js, big.js, or BigDecimal. For most purposes, multiply by a power of ten to convert decimals to integers (e.g., $123.45 → 12345 cents) and divide back at the end.

Effectively no — BigInt grows as needed up to the limits of your browser's available memory. Multiplication of 10,000-digit numbers takes a fraction of a second; arithmetic on 1,000,000-digit numbers can take seconds. Cryptographic-strength sizes (2,048–4,096 bits, ~600–1,200 digits) are easy.

Number theory and combinatorics built for big integers: <code>gcd</code>/<code>lcm</code> (any number of args), <code>modpow(a,e,m)</code> for fast modular exponentiation (handles negative exponents via the modular inverse), <code>modinv(a,m)</code>, <code>sqrt</code>/<code>isqrt</code> (exact integer square root), <code>root(k,n)</code> (integer k-th root), <code>fact(n)</code> and postfix <code>n!</code>, <code>ncr(n,k)</code>/<code>npr(n,k)</code>, <code>fib(n)</code>/<code>lucas(n)</code> by fast doubling, <code>isprime(n)</code> (Miller–Rabin), <code>nextprime(n)</code>, plus <code>abs sign min max bitlength popcount mod</code>.

<code>/</code> is integer (truncating) division — <code>100 / 7</code> = 14. <code>%</code> gives the remainder with the dividend's sign (<code>100 % 7</code> = 2), while the <code>mod(a,m)</code> function returns the always-non-negative mathematical modulus. The two differ only for negative inputs.

It's a Miller–Rabin test with the witness set {2,3,…,37}, which is <em>deterministic</em> (provably correct) for every n below 3.3 × 10²⁴. Above that it's a very strong probabilistic test — no known composite passes this witness set — but not a formal proof. For cryptographic primality proving, use a dedicated tool.

Double-precision IEEE 754 floats give about 15–17 significant decimal digits. For amounts that fit comfortably in that range (typical business calculations, most measurements), regular floats are fine and faster. For currency, dates, and any integer that might exceed 9 × 10¹⁵, BigInt is the safe choice.

Simply type your numbers and read the result, which refreshes the instant you change something. There is nothing to submit and nothing to wait for.

Not at all — it runs in the browser with nothing to install and no account. After it loads once, it even works without an internet connection.

Yes. Everything happens in your browser. Nothing you type is sent to a server or saved anywhere.