Number Converter
Number Converter converts between number systems, including binary, hexadecimal and Roman numerals, free and in your browser. You enter a number in one system, and get its value in the others.
Last updated: 30 October 2026 · Free · No signup
Different number systems are used in different fields. Computers use binary, web colours and programming often use hexadecimal, and Roman numerals are still used for clocks, book chapters, and outlines. Converting by hand is possible for small numbers, but it becomes slow and error-prone for larger ones, especially between binary and hexadecimal. This tool does the conversion in both directions.
Check the base you are converting from before you enter a number, because the same digits mean different things in different bases. The digits '10' mean ten in decimal, two in binary, and sixteen in hexadecimal, so the starting base matters more than the digits themselves.
Privacy: this tool runs entirely in your browser — no upload, no signup, and your files never leave your device.
Convert a number between Binary, Octal, Decimal and Hex — and convert Roman numerals (I, V, X, L…) in both directions.
Base Converter
Roman Numerals
How to use Number Converter
- Enter the number you want to convert.
- Choose the system it is currently in.
- Read its value in the other systems.
- Copy the value you need.
Key facts
| Systems | Decimal, binary, hexadecimal, octal, and Roman numerals |
|---|---|
| Input | A number, plus the system it is in |
| Upload | None — conversion happens in your browser |
Frequently asked questions
How do I convert binary 1010 to decimal?
Binary 1010 means 8 + 0 + 2 + 0, which is 10 in decimal. Each binary digit represents a power of two, starting from the right, so you add the powers where the digit is 1 and ignore those where it is 0.
What is hexadecimal used for?
Hexadecimal, base 16, is used in computing and web design because it represents binary data compactly. Web colours are a common example: a colour code such as #FF0000 is hexadecimal, with FF meaning 255 in decimal for the red part.
How do Roman numerals work?
Roman numerals use letters for values: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500, and M is 1000. Smaller values before larger ones are subtracted, so IV is 4 and IX is 9, while larger values before smaller ones are added.
Are my converted numbers uploaded or saved?
No. Conversion happens in your browser only. Nothing is sent to a server and nothing is saved after you close the page.