Binary ↔ octal ↔ decimal ↔ hex — type in any field, the others update instantly. Handles numbers of any size.
The base (or radix) is how many digit symbols a number system uses. Decimal uses ten (0–9); binary uses two (0–1); hex uses sixteen (0–9 then A–F, where A=10 and F=15).
Hardware stores everything as on/off states, so all data is ultimately binary. Hex is popular with programmers because each hex digit maps to exactly 4 bits — FF is 11111111.
A web color like #667EEA is three hex bytes — red 66 (102), green 7E (126), blue EA (234). Converting hex↔decimal is exactly what this tool does.
This converter uses arbitrary-precision integers, so 100-digit numbers convert exactly — no rounding at 15 digits like calculators that rely on floating point.
Beyond 9, digits continue with letters: base 36 uses 0–9 plus A–Z. Base-36 strings are the densest identifiers that stay case-insensitive and URL-friendly.
A leading minus sign works in every field. (Note this shows mathematical negation, not two's-complement bit patterns used inside CPUs.)