Online Tool Store
Arbitrary Precision Calculator
Add, subtract, multiply, or divide integers of any length with exact BigInt math — no 15-17 digit rounding limit like a normal calculator. Runs in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Arbitrary Precision Calculator
Exact arithmetic on very large or high-precision numbers — powered by BigInt, never floating point.
Try an example
Result
Runs entirely in your browser — nothing is uploaded. Integer results are always exact; decimal results are rounded to the chosen precision only when the true value does not terminate.
How the Arbitrary Precision Calculator works
- Type a number of any length — whole or decimal, positive or negative — into Number A and Number B; the sample fields already hold 27- and 18-digit numbers.
- Pick an operation: addition, subtraction, multiplication, division, modulo, or power, and set a decimal precision for division results.
- The result recomputes on every keystroke using a BigInt-backed fixed-point representation, which stores digits exactly rather than as floating-point approximations.
The method
A standard JavaScript Number loses precision past 2^53 because it's stored in 64 bits shared between the integer and fractional parts. This tool instead stores each number as a BigInt integer plus a decimal scale (value / 10^scale), so arithmetic stays exact regardless of digit count, and division rounds only at the precision you choose.
result = bigIntValue(a) {+, -, ×, ÷, mod, ^} bigIntValue(b); for whole-number division: quotient = a / b, remainder = a % b
Example: 987654321987654321987654321 × 123456789123456789 produces an exact 45-digit product — a calculation that would silently round in ordinary floating-point arithmetic.
FAQ
Why does JavaScript need a special tool for this — doesn't it already do math?
Regular JavaScript numbers are IEEE-754 doubles, accurate only up to about 2^53 (roughly 9 quadrillion). Beyond that they silently lose precision. This tool represents every number as a BigInt-backed fixed-point value, so results stay exact no matter how many digits you enter.
What happens with division — do I get a decimal?
Yes. Division computes a fixed-point decimal to the number of decimal places set in "Precision," rounding half up on the final digit. If both numbers you entered are whole integers, the result panel also shows the exact integer quotient and remainder underneath.
Is there a limit to how large my numbers can be?
Whole-number inputs have no fixed upper bound beyond your browser's available memory. Results are capped at 100,000 digits and the exponent in Power is capped at a magnitude of 100,000, both just to keep the page responsive.
Can I use decimals with this calculator?
Yes — enter decimal numbers directly in Number A or B (e.g. 22 ÷ 7), and set how many digits after the decimal point you want in the Precision field (1 to 500).
Does it support negative numbers?
Yes — enter a leading minus sign on Number A or B to get an exact signed result for any of the six operations.
What operations are available besides the four basic ones?
Addition, subtraction, multiplication, division, modulo, and power (exponentiation) are all supported, each computed with exact BigInt-based arithmetic rather than floating point.
How we compare
| Feature | Online Tool Store | A spreadsheet formula | A standard calculator app |
|---|---|---|---|
| Exact results beyond 15-17 significant digits | ✓ | ✗ | ✗ |
| Shows integer quotient and remainder together | ✓ | ✗ | ✗ |
| No install, runs in your browser | ✓ | ✓ | ✗ |
Spreadsheets and pocket calculators round once numbers get large; this tool uses BigInt to keep every digit exact, which matters for things like cryptography-scale numbers or factorial calculations.