How to convert binary, octal, decimal, and hex
Integer base conversion in the browser with parseInt — not IEEE floats, not two’s-complement tutorials, and not hex encoding of text.
What the dropdowns mean
Number Base Converter at /tools/number-base-converter maps pairs such as Decimal → Hex (10-16), Binary → Decimal (2-10), Hex → Binary (16-2), and the other common teaching pairs. Input is trimmed of spaces. parseInt with the source base must succeed or you get an error. Output is uppercase for hex. This is for whole numbers that fit JavaScript’s integer parsing, not for 256-bit crypto keys.
Steps
1) Open Number Base Converter. 2) Choose the direction that matches your homework or datasheet. 3) Paste 255 for decimal→hex (FF) or 11111111 for binary→decimal (255). 4) Copy the result. Leading 0x is not required; hex letters A–F work. Binary should only contain 0 and 1.
Hex text vs hex numbers
Hex Encode / Decode at /tools/hex-encode-decode turns UTF-8 text into byte hex (h e l l o → 68656c6c6f) or back. That is not “the number hello.” Color Converter uses #RRGGBB, which is hex channels, not a positional integer lesson. Hash Generator prints a SHA digest as hex. Use the number-base page when the value is a magnitude (255, 0xFF, 11111111).
Worked example
Decimal 10 → binary is 1010. Decimal 255 → hex is FF. Hex A → decimal is 10. Octal 10 → decimal is 8. If you paste “255.5”, parsing fails — integers only. Overflow of huge digit strings can yield Infinity or a wrong truncated value; keep inputs realistic.
Limits
No base-64 here (that is Base64 Encode). No IEEE-754 bit patterns. No two’s complement negative binary display. Related: /tools/hex-encode-decode, /tools/base64-encode, /tools/color-converter.
Privacy
Numbers stay in the tab. Nothing is uploaded. Close the page if the value is a license key you should not leave on screen.