Big Number Calculator

1. Enter your large integers. Type or paste any integer into the A and B fields. The calculator handles numbers with hundreds or thousands of digits. You can include commas or underscores as separators (they are stripped automatically). Negative numbers are supported: prefix with a minus sign.
2. Select an operation. Choose addition, subtraction, or multiplication. Results are computed instantly using JavaScript BigInt, which provides exact arbitrary-precision integer arithmetic with no rounding error.
3. Read the result. The result is displayed with comma formatting for readability, along with a digit count. For multiplication of two 30-digit numbers, you may get a 59 or 60-digit result.

Example: 123,456,789,012,345,678,901,234,567,890 multiplied by 987,654,321,098,765,432,109,876,543,210 produces a 60-digit result that no standard floating-point calculator can handle exactly.

Standard JavaScript numbers (float64):
  Safe integer range: -(2^53-1) to (2^53-1)
  = -9,007,199,254,740,991 to 9,007,199,254,740,991
  Beyond this range, results are rounded and inaccurate.

JavaScript BigInt:
  Arbitrary precision integers with no upper bound.
  Operations: + - * / % ** (no floating-point operations)
  All results are exact integers.

Example — standard float fails:
  9007199254740992 + 1 = 9007199254740992 (WRONG, rounds!)

Example — BigInt is exact:
  9007199254740992n + 1n = 9007199254740993n (correct)

Large multiplication example:
  A = 123,456,789 × 10^21 (30 digits)
  B = 987,654,321 × 10^21 (30 digits)
  A × B has up to 60 digits
  Every digit is computed exactly.

Addition algorithm (grade school):
  Align digits by place value, add column by column,
  carry the 1 when the sum exceeds 9.
  BigInt automates this for any number of digits.

Multiplication algorithm (schoolbook or Karatsuba):
  For very large numbers, Karatsuba reduces complexity
  from O(n²) to O(n^1.585), making billion-digit
  multiplication feasible.