Morse Code

This calculator turns a sending speed in words per minute (WPM) into exact Morse code timings, which is handy when setting up a keyer, a tone generator, a practice app or a microcontroller sketch.

How the calculation works

All Morse timing is built from one unit: the length of a dot. A dash lasts 3 units, the gap between elements inside a character 1 unit, the gap between letters 3 units and the gap between words 7 units (as in ITU-R Recommendation M.1677). Speed is measured with the reference word PARIS, which takes exactly 50 units including the space after it. So one dot in milliseconds equals 60,000 / (50 × WPM) = 1200 / WPM.

Enter a speed between 1 and 80 WPM. The calculator returns the dot, dash, letter gap and word gap in milliseconds, plus an approximate characters-per-minute figure, which assumes the standard five-character word (WPM × 5).

Worked example

At 20 WPM a dot lasts 1200 / 20 = 60 ms, a dash 180 ms, the gap between letters 180 ms and the gap between words 420 ms; the gap inside a character equals one dot, 60 ms. That is roughly 100 characters per minute. At a beginner pace of 5 WPM the dot stretches to 240 ms and a word gap to 1.68 seconds.

Things to keep in mind

• PARIS gives an average speed for plain-language text. Some tests of random code groups use the CODEX reference word (60 units), which means shorter elements at the same nominal WPM.
• Farnsworth timing (characters sent fast, extra space between them) is not modeled here; the gaps are the standard proportional ones.
• If you generate the tone in software, add a few milliseconds of rise and fall time to each element, otherwise you will hear key clicks at higher speeds.
• Above 40 WPM a dot is shorter than 30 ms, so check that your receiver or decoder can resolve pulses that short.