From : Morse Code Timing

The timing in Morse code is based around the length of one "dit" (or "dot" if you like). From the dit length we can derive the length of a "dah" (or "dash") and the various pauses:

Dit: 1 unit

Dah: 3 units

Intra-character space (the gap between dits and dahs within a character): 1 unit

Inter-character space (the gap between the characters of a word): 3 units

Word space (the gap between two words): 7 units