Don's Tools · Converters · Base Converter

Base converter

Convert numbers between binary, octal, decimal, hex and any base, right in your browser. Nothing is uploaded.

Input base
Works offline: conversion happens in your browser with big-integer precision, so very large whole numbers convert exactly. Nothing is uploaded.
Base Converter is a free tool that converts whole numbers between binary, octal, decimal, hexadecimal and any base from 2 to 36, entirely in your browser with nothing uploaded. It uses big-integer maths so very large numbers convert exactly, validates the digits for the chosen base, and updates all results live as you type.

Frequently asked questions

Is my data uploaded anywhere?

No. The conversion runs entirely in your browser and nothing is uploaded. It works offline once the page has loaded.

Which bases are supported?

Binary, octal, decimal and hexadecimal directly, plus any custom base from 2 to 36 for both reading your input and showing an extra result.

Can it handle very large numbers?

Yes. It uses big-integer maths, so even numbers far beyond the usual limits convert exactly without rounding.

What characters can I use?

Digits 0 to 9 and letters A to Z, where A means 10 up to Z meaning 35. A leading minus sign is allowed for negative numbers. Invalid digits for the chosen base are flagged.

Does it work with decimals or fractions?

It converts whole numbers (integers). Fractional values are not supported, which keeps results exact for programming and digital uses.