Number Base Converter

How to Convert a Number Between Bases

Enter a positional number, choose its source base, and select the target base. Auto detect recognizes the common 0b, 0o, and 0x prefixes; unprefixed auto-detected values are treated as decimal. Review the target result or compare it with the common-base outputs, then copy or download the conversion report.

1. 1. Enter the value

   Use digits valid for the source base. A leading sign and one radix point are supported.

2. 2. Select the bases

   Choose Auto detect or an explicit source from base 2 to 36, then select the target base.

3. 3. Copy or export

   Compare exact and truncated results, copy one value, or download every displayed base.

How Positional Number Systems Work

In positional notation, every digit is multiplied by a power of the base. For example, hexadecimal 2D equals 2 × 16¹ + 13 × 16⁰, which is decimal 45. Positions after the radix point use negative powers, so binary 101.01 equals 1 × 2² + 1 × 2⁰ + 1 × 2⁻², or decimal 5.25.

Exact and Repeating Fractional Results

A fraction may terminate in one base and repeat in another. Decimal 0.5 is exactly 0.1 in binary, while decimal 0.1 becomes a repeating binary fraction. The converter keeps the entered value as an exact rational number, generates up to the selected number of fractional digits, and labels any unfinished expansion as truncated rather than exact.

Truncation is different from rounding: the tool stops after the precision limit without changing the final digit. Increase the precision when you need more digits, but remember that a repeating representation never terminates.

Large Integers Without Floating-Point Loss

Ordinary JavaScript numbers cannot represent every integer above 9,007,199,254,740,991 exactly. This tool parses digits into BigInt values and stores fractions as a reduced numerator and denominator, so long identifiers, masks, and numeric constants remain exact within the 4,096-digit input limit. The output is a mathematical signed value, not a fixed-width two’s-complement encoding.

Prefixes, Separators, and Valid Digits

Auto detect recognizes 0b for binary, 0o for octal, and 0x for hexadecimal. Spaces and underscores are ignored, which makes long values easier to read. Letters are case-insensitive on input. Scientific notation is not interpreted as an exponent; every character is treated as a positional digit, so use the full numeric value when converting decimal scientific notation.

JavaScript Number References

The MDN documentation explains BigInt arbitrary-precision integers and binary, octal, and hexadecimal numeric literal prefixes. External references open in a new tab.

Private, Browser-Based Conversion

Number parsing, exact arithmetic, copying, and TXT report creation run locally in your browser. Values do not need to be uploaded for conversion, and refreshing the page clears the current workspace.

Continue Your Developer Workflow

Plan IPv4 networks and inspect address bits with the Subnet Calculator, compare hexadecimal digests using the Hash Generator, or encode text and bytes—not numeric values—with the Base64 Text Encoder & Decoder. For measurement conversions instead of numeral systems, use the Unit Converter.

Number Base Converter FAQs