How Morse Code WPM Is Calculated: The PARIS Standard and 1:3:7 Timing

Everything Starts with the Dot: The 1:3:7 Rule

All Morse timing is measured in dot units. Per Recommendation ITU-R M.1677-1:

• A dot is 1 unit; a dash is 3 units
• The gap between elements within one letter is 1 unit
• The gap between letters is 3 units; between words, 7 units

These 1:3:7 ratios never change — "speed" simply means compressing or stretching the entire timeline proportionally.

Why the Standard Word Is PARIS

The trouble with WPM (words per minute) is that every English word has a different Morse length, so "20 words per minute" first needs a definition of "one word." The international convention uses PARIS, because — including the word gap that follows it — it is exactly 50 units long, close to the average length of English text:

Letter	Code	Calculation	Units
P	.--.	1+1+3+1+3+1+1	11 + 3 (letter gap)
A	.-	1+1+3	5 + 3
R	.-.	1+1+3+1+1	7 + 3
I	..	1+1+1	3 + 3
S	...	1+1+1+1+1	5 + 7 (word gap)
Total			50

This gives "20 WPM" a precise meaning: PARIS can be sent twenty times per minute — 1,000 units per minute.

How Long Is a Dot? The 1.2-Second Formula

From there the standard conversion formula follows directly. A minute has 60 seconds, and N WPM means 50 × N units per minute, so:

dot length (seconds) = 60 ÷ (50 × N) = 1.2 ÷ WPM

At 20 WPM a dot is 60 ms and a dash is 180 ms; at 5 WPM a dot stretches to 240 ms. The speed slider (5–30 WPM) in our Morse code translator uses exactly this formula.

Character Speed vs. Effective Speed

Practice material is often labeled something like "18 WPM characters / 5 WPM effective." That is Farnsworth timing: each character keeps its crisp 18 WPM rhythm, but the gaps between characters and words are stretched so the overall rate drops to 5 WPM. The ARRL published a formal standard for this hybrid timing, giving "slow practice" a precise, reproducible definition.

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