Convert numbers between binary, octal, decimal, and hexadecimal online for free. Instant conversion across all bases at once. No signup required.
First time here? Type a number into any base field Your input is processed locally and disappears when you close the tab.
Binary, octal, decimal, hexadecimal — computing runs on all four, and translating between them by hand is error-prone exactly when accuracy matters most. Our free Number Base Converter shows the same value in all four bases simultaneously: type into any field and the other three update live.
The converter is built for real developer workloads. It accepts standard prefixes (0x, 0b, 0o), uses BigInt arithmetic so 64-bit values and beyond convert exactly rather than silently losing precision, and gives every representation a one-click copy button.
Reach for it when reading hex dumps and memory addresses, crafting bitmasks and permission flags (chmod's octal lives here), decoding network captures, or explaining two's complement to a student. Everything runs locally in your browser. For encoding text rather than numbers, see our Base64 Encoder / Decoder or the HTML Entity Encoder.
Type a number into any base field
Watch the other three bases update live
Use 0x, 0b, or 0o prefixes if you prefer
Copy any representation with one click
Clear and convert the next value