Converters
Convert units, numbers, dates and more.
About converters
Converters for the everyday translation problems that are not unit conversions: number bases, timestamps, Roman numerals, Morse code, colour formats and date arithmetic.
The timestamp converter is the one developers reach for most. Unix time counts seconds since 1 January 1970 UTC, which is why logs, databases and APIs store it โ one unambiguous integer, no timezone, no locale, no daylight-saving edge cases. It is also completely unreadable to a human, so debugging anything time-related means converting constantly. Watch the units: JavaScript's Date.now() returns milliseconds while most backends and Unix tools use seconds, and mixing the two produces dates in 1970 or in the year 56000.
The base converter matters for the same category of work. Hexadecimal is compact for binary data because each digit maps to exactly four bits, which is why colours, memory addresses and byte values are written that way. Binary makes bit flags and permission masks legible. Octal survives almost entirely because Unix file permissions use it โ the 755 in chmod 755 is three octal digits, each encoding read, write and execute as bits.
Frequently asked questions
Is a Unix timestamp in seconds or milliseconds?
Traditionally seconds โ the count since 1 January 1970 UTC. JavaScript is the common exception, since Date.now() returns milliseconds. A quick check: a current timestamp in seconds is about 10 digits, in milliseconds about 13. If your converted date lands in 1970 or thousands of years from now, you have mixed the two.
Why do developers use hexadecimal?
Because it maps cleanly onto binary: one hex digit is exactly four bits, so a byte is always two hex digits. That makes binary data compact and readable, which is why colour codes, memory addresses and byte dumps all use it.
Why are Unix file permissions written in octal?
Because permissions come in groups of three bits โ read, write and execute โ and one octal digit represents exactly three bits. So 755 means owner read/write/execute (7), group read/execute (5), others read/execute (5). It is a historical convention that survives because it maps perfectly onto the underlying bits.
Do these conversions happen in my browser?
Yes. Every converter here is pure arithmetic or string manipulation running locally, so nothing you enter is transmitted and all of them work offline once loaded.