---
title: "Number base converter — free, runs in your browser"
description: "Convert between binary, octal, decimal, hexadecimal and any base from 2 to 36. Free, no sign-up, and nothing you enter leaves your browser."
url: https://atoneplace.net/tools/number-base-converter/
site: "At One Place"
---

# Number base converter

Convert between binary, octal, decimal, hexadecimal and any base from 2 to 36.

## How it works

Converts a number between any two bases from 2 to 36, showing binary, octal, decimal and hex simultaneously.

Base 36 is the practical ceiling because it uses all ten digits plus all twenty-six letters. Beyond that there are no conventional symbols left.

Hexadecimal is used in computing because the conversion to binary is trivial: each hex digit maps to exactly four bits, with no arithmetic. Octal does the same for three bits, which is why Unix file permissions are written in octal — each digit is exactly one read/write/execute triple.

The bit width is shown alongside, since that is usually the reason for converting. A value that needs 33 bits will not fit in a 32-bit integer, and that is the kind of thing this is used to check.

> This tool runs entirely in your browser. Nothing you enter is sent to a server, logged or stored, and the page keeps working with the network disconnected.

## Common questions

### Why does computing use hexadecimal?

Each hex digit is exactly four bits, so converting to and from binary needs no arithmetic — just substitution.

### Why are Unix permissions in octal?

Each octal digit is exactly three bits, matching the read, write and execute triple for owner, group and others.

### What is the highest base?

Base 36 in common use, because that exhausts the ten digits and twenty-six letters. Higher bases need invented symbols.

## Related pages

- [Image format converter and compressor](https://atoneplace.net/tools/image-converter/)
- [Unix timestamp converter](https://atoneplace.net/tools/unix-timestamp-converter/)
- [SVG to PNG converter](https://atoneplace.net/tools/svg-to-png/)
- [Cron expression parser](https://atoneplace.net/tools/cron-expression-parser/)
- [Mouse sensitivity and FOV converter](https://atoneplace.net/tools/mouse-sensitivity-converter/)
- [CSV to JSON converter](https://atoneplace.net/tools/csv-to-json/)
- [Screen resolution and display info](https://atoneplace.net/tools/screen-resolution-checker/)
- [Percentage calculator](https://atoneplace.net/tools/percentage-calculator/)
- [Loan and EMI calculator](https://atoneplace.net/tools/loan-calculator/)
- [BMI calculator](https://atoneplace.net/tools/bmi-calculator/)

## Sources

- Calculated on this page — At One Place (/about/)