What is it?
The Big Number Calculator works with whole numbers of any length, exactly, where normal calculators round after about 15–16 digits.
Who is it for?
Programmers, maths enthusiasts, and students working with numbers too long for normal calculators.
How to use it
Type the First number (any length, whole) and the Second number. The results include sum, difference, product, quotient, Remainder (a mod b), GCD and Digits in a × b. The answer appears as you type; there is no Calculate button. Tap Copy result to copy it, or Share on WhatsApp to send it.
Why normal calculators fail
Most calculators and spreadsheets store numbers with about 15–16 significant digits. 12345678901234567890 + 1 shows no change in Excel. This tool keeps every digit.
Uses
- Factorials and large powers in combinatorics and cryptography.
- Checking long account numbers, IDs and checksums (mod).
- Programming problems with very large integers.
Limits
Only whole numbers: no decimals. Division gives a whole-number quotient and a remainder. Spaces and commas in pasted numbers should be removed.
Worked examples
- 2⁶⁴ = 18,446,744,073,709,551,616 exactly, where a normal calculator shows 1.8447e19.
- 123456789123456789 × 987654321987654321 gives all 36 digits.
- Remainder of a 20-digit number mod 97 checks IBAN-style codes.
- 25! (25 factorial) has 26 digits: 15,511,210,043,330,985,984,000,000.
Errors and how to fix them
- “Use whole numbers only (digits, with an optional minus sign)”: remove decimals, commas and spaces.
Open the tool: Big Number Calculator
Still stuck?
Contact support. Tell us which tool or page you were using, what you tapped, what you saw, and your phone or computer and browser (for example: Android phone, Chrome). We reply by email.
Questions, or an error not listed here?
Tell us in the comments: what you were doing, the exact message you saw, and your device and browser. We read every comment and add new fixes to this article.