number base

Convert integers between binary, octal, decimal, and hex with live sync and shareable permalinks.

Overview

number base is a browser-based integer base converter. Type a number into any of the four panels and all others update instantly. No server involved — everything runs in the browser using JavaScript's built-in parseInt and Number.prototype.toString.

Supports non-negative integers up to Number.MAX_SAFE_INTEGER (2⁵³ − 1).

Panels

The tool shows four panels side by side:

Panel	Base	Prefix
Binary	2	`0b`
Octal	8	`0o`
Decimal	10	—
Hex	16	`0x`

Edit any panel — the other three update on every keystroke. Hex output is always uppercase (FF, not ff).

Conversion

Conversion goes through decimal as an intermediate step:

// Any base → decimal
const n = parseInt(input, fromBase);

// Decimal → all bases
n.toString(2)   // binary
n.toString(8)   // octal
n.toString(10)  // decimal
n.toString(16).toUpperCase()  // hex

Validation

If you type characters that are invalid for the selected base (e.g. 2 in a binary field, or G in a hex field), an invalid badge appears on that panel and the other panels are not updated. Fix the input and conversion resumes immediately.

Permalinks

The URL updates live as you type. One query parameter is used:

value — the current value as a decimal integer

/numbase?value=255

Restores 11111111 in binary, 377 in octal, 255 in decimal, and FF in hex.

Use the Copy button in the Permalink row to copy the current URL to your clipboard.

Use the Reset button to clear all panels and return the URL to the bare /numbase path.