Which number bases are supported?

Binary (base 2), octal (base 8), decimal (base 10) and hexadecimal (base 16). Enter a value, pick the base it is written in, and all four representations update instantly.

No. The conversion runs entirely in your browser using built-in JavaScript number methods — nothing is sent to a server.

Why does it reject some inputs?

Each base only allows certain digits — binary allows 0 and 1, octal 0–7, and hexadecimal 0–9 plus A–F. If a digit is not valid for the chosen base, the tool shows an error instead of a wrong answer.

Number Base Converter — Binary, Octal, Decimal, Hex (No Upload)

Number Base Converter

Convert a whole number between binary, octal, decimal and hexadecimal — type a value, choose the base it’s written in, and see all four representations update live. Free, validated, and 100% in your browser.

Value

From base

Binary

Octal

Decimal

Hexadecimal

Tip: switch the “From base” dropdown to interpret the same input as binary, octal, decimal or hex.

🔒 100% private — runs in your browser, never uploaded.

How to use the base converter

Type a number in the Value box — for example 255.
Pick the “From base” that matches how your number is written (decimal, binary, octal or hex).
Read the binary, octal, decimal and hexadecimal results below — they recalculate on every keystroke.
Copy any result with the button beside it.

What are number bases?

A number base (or radix) is simply how many distinct digits a counting system uses before it rolls over to the next place value.Decimal (base 10) is what we use day to day — digits 0–9. Binary (base 2) uses only0 and 1 and is the native language of computers. Octal (base 8) groups bits in threes and still shows up in Unix file permissions, while hexadecimal (base 16) packs four bits into one digit using0–9 and A–F, making it the go-to for colours, memory addresses and byte dumps.

Converting between them is a routine task in programming, electronics and digital design. For instance, the decimal value255 is 11111111 in binary, 377 in octal and FF in hex — the largest value a single byte can hold. This tool reads your input in the base you choose and re-expresses the exact same quantity in every other base.

Is it private?

Yes. Everything happens locally in your browser using JavaScript’s built-in parseInt and Number.toStringmethods — there is no server round-trip, no logging and no upload. You can even use it offline once the page has loaded, which makes it safe for converting values from internal systems, hardware registers or anything you’d rather not paste into a remote service.

Frequently asked questions

Does it handle hexadecimal letters in any case?

Yes. You can enter hex digits as upper- or lower-case (for example ff or FF); results are shown with upper-case hex for readability.

What’s the largest number I can convert?

It uses standard JavaScript numbers, so it’s reliable for integers up to 2⁵³ − 1 (9,007,199,254,740,991). Beyond that, very large values can lose precision, so the tool sticks to safe integers.

Can I convert negative numbers or decimals?

This tool focuses on non-negative whole numbers, which covers the vast majority of base-conversion needs. Fractions and signed/two’s-complement values aren’t supported.