Which number bases can this tool convert between?

It handles the four most common bases: binary (base 2), octal (base 8), decimal (base 10), and hexadecimal (base 16). Pick any base as the source and any base as the target using the two dropdowns.

Why does it say my number is invalid?

Each base only allows certain digits. Binary accepts 0 and 1, octal accepts 0 to 7, decimal accepts 0 to 9, and hex accepts 0 to 9 plus A to F. If your input has a digit that does not belong to the From base, the tool asks you to fix it.

Is my number sent to a server?

No. The whole conversion runs in your browser, so the value you type never leaves your device. It keeps working offline once the page has loaded.

Does hexadecimal need to be uppercase or lowercase?

Either works. You can type FF or ff for hex input, and the converter reads both the same way.

Number Base Converter

Input

From base

To base

Output

What the Number Base Converter does

This tool converts a single number from one numeral system to another. You type a value, choose what base it is written in, choose what base you want it turned into, and get the answer right away. It covers binary (base 2), octal (base 8), decimal (base 10), and hexadecimal (base 16), which are the four bases that come up most often in programming and computer science.

It helps students checking homework, developers reading memory addresses or color codes, and anyone who needs a quick, accurate conversion without doing the math by hand.

How to use it

Type or paste your number into the input box.
Open the From base dropdown and pick the base your number is currently written in (binary, octal, decimal, or hex).
Open the To base dropdown and pick the base you want the result in.
Read the converted value in the output box. It updates as you type, and you can also press Convert to run it.

If a digit does not fit the From base, the tool shows a short message so you know what to correct.

A quick worked example

Take the decimal number 255. Set From to decimal and To to hexadecimal and you get FF. Switch To to binary and the same value becomes 11111111. This is why 255 shows up so often in color and byte work: it is the largest value a single byte can hold.

The converter runs entirely in your browser, so your input stays private on your device. It is free, needs no sign-up, and works the same on desktop or phone.

Frequently asked questions

Which number bases can this tool convert between?: It handles the four most common bases: binary (base 2), octal (base 8), decimal (base 10), and hexadecimal (base 16). Pick any base as the source and any base as the target using the two dropdowns.
Why does it say my number is invalid?: Each base only allows certain digits. Binary accepts 0 and 1, octal accepts 0 to 7, decimal accepts 0 to 9, and hex accepts 0 to 9 plus A to F. If your input has a digit that does not belong to the From base, the tool asks you to fix it.
Is my number sent to a server?: No. The whole conversion runs in your browser, so the value you type never leaves your device. It keeps working offline once the page has loaded.
Does hexadecimal need to be uppercase or lowercase?: Either works. You can type FF or ff for hex input, and the converter reads both the same way.

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Last updated: June 17, 2026