Big Number Calculator
Exact arithmetic on integers with hundreds — or thousands — of digits. Add, subtract, multiply, divide, factorial, power, GCD, LCM, and primality testing, with no rounding, ever.
7
OPERATIONS
Exact
PRECISION
10,000!
MAX FACTORIAL
Big Integer Arithmetic
Result (Add)
1,111,111,111,111,111,111,111,111,111,110
31
Result Digits
+
Operation
🔣 Famous Big Numbers — Click to Load
What Is Arbitrary-Precision Arithmetic?
Ordinary computer arithmetic stores every number in a fixed-size box — 64 bits for a standard floating-point number — which caps how many digits it can represent exactly. Arbitrary-precision (or “bignum”) arithmetic drops that fixed box entirely: instead of packing a number into a fixed number of bits, it stores it as a growable sequence of digits, the way you’d write it out by hand on paper. Addition, subtraction, and multiplication then work digit-by-digit, exactly as long-multiplication does in grade school, just carried out by the computer instead of a pencil. The trade-off is speed and memory rather than accuracy — a 300-digit multiplication takes more work than a 3-digit one — but the result is always exact, never approximated.
A Worked Example
Multiply two 20-digit numbers — 98,765,432,109,876,543,210 × 12,345,678,901,234,567,890 — with regular floating-point math and the last several digits of the answer are unreliable, because the true 40-digit result can’t fit inside a 64-bit float’s ~16-digit precision budget. Run the same multiplication through this calculator’s BigInt engine and every one of those 40 digits comes back correct:
1,219,326,311,370,217,952,237,463,801,111,263,526,900➕
Core Operations
Add, subtract, multiply, divide (with remainder), modulo, GCD, and LCM — all on integers of any length, computed exactly.
❗
Factorial
N! grows explosively — 100! already runs to 158 digits. Computed digit-exact up to 10,000! before the browser-safety cap kicks in.
⚡
Power
Raise any base to any non-negative exponent, exact to the last digit, capped at an exponent of 10,000 to stay browser-safe.
🔍
Analyze
Check digit count, digit sum, parity, sign, and run a Miller-Rabin primality test on any integer you enter.
— FAQ