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Arbitrary-Precision Number Base Converter

Convert an integer without routing it through floating-point arithmetic. Use binary, octal, decimal, hexadecimal or another base through 36, then format the output for inspection or reuse.

Browser-based · No account required · Copy and export

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BUILT FOR THE DETAILS
  1. 01Add your input
  2. 02Inspect & adjust
  3. 03Use your result
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This converts integer positional numeral systems, not Base64 text encoding. Fractions and scientific notation are not supported.

How to use Arbitrary-Precision Number Base Converter
  1. Choose the input and output bases. Enter a signed integer; optional underscores separate digits.
  2. A 0b, 0o or 0x prefix is accepted only when it matches the selected input base. Choose output case and optional grouping.
  3. Convert, review the result and common-base equivalents, then copy, download or swap it into the opposite direction.
When to use this tool
Inspect integer values used in code, binary flags or hexadecimal data. BigInt preserves exact integers, while fractions and floating-point conversions are outside this workflow.
BigInt avoids unsafe integer rounding
JavaScript Number cannot represent every integer beyond its safe range. This converter accumulates digits as a BigInt and prints in the chosen radix, so large integer identifiers can retain their exact value. Bases above ten use letters for additional digits. Output underscores are visual separators, not fractional points, and can be reused as input here.
Worked example
Decimal input: 9007199254740993
Hexadecimal: 20000000000001
Hex input: 0xFF (select base 16)
Decimal result: 255
Limits and output checks
Integers only: fractions, scientific notation and fixed-width two's-complement interpretation are not implemented. Negative values use a minus sign. Input is bounded to 10,000 characters. A radix prefix never silently overrides the base you selected.
Reference: JavaScript BigInt.
Frequently asked questions
Can I paste 0xFF?
Yes, with base 16 selected. A mismatched prefix produces an error instead of guessing another base.
Does grouping change the number?
No. Underscores group the output digits for readability and are ignored when parsing input in this tool.
Can I convert a negative binary value?
Use a leading minus sign for a signed mathematical integer. The tool does not infer a bit width or decode two's-complement representations.
Convert an integer without guessing its radix
Select the source and destination bases explicitly. Check sign and prefix handling before using the output as an identifier or fixture value.
Scope of this workflow
This is integer conversion, not fractional conversion or fixed-width two’s-complement interpretation. A prefix does not override the selected source base.
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