Why timing matters more than the chart
International Morse is a rhythm code. A listener recognizes letters by how long each tone lasts and how long the silences last between tones. ITU-R M.1677-1 fixes those ratios: one time unit for a dot, three for a dash, one unit between elements inside a character, three units between letters, and seven between words. Charts show which dots and dashes belong to each letter; timing explains why two letters with the same number of marks still sound different on the air.
Software on MorseCoder follows the same ratios when it plays audio or flashes light. If your ear says a letter feels “rushed,” the problem is usually a missing intra-letter gap, not a wrong dot count. That is why trainers emphasize Farnsworth spacing: keep each letter at full speed while stretching the pause before the next letter.
The PARIS standard and fifty units
Amateur and commercial CW speeds are quoted in words per minute (WPM). The conventional reference word is PARIS. Count its elements with ITU rules: P (.--.) uses ten units, A (.-) five, R (.-. ) seven, I (..) four, S (...) seven, plus three units between each letter and seven after the word. The total is fifty timing units for one standard word.
Because fifty units define one word-minute, the duration of one unit in milliseconds is 1200 divided by WPM. At 20 WPM each unit lasts 60 ms, so a dot is about 60 ms and a dash about 180 ms. At 15 WPM a unit is 80 ms. This formula is independent of Farnsworth: Farnsworth changes gaps between letters, not the length of dots and dashes inside a character.
PARIS is a measuring stick, not a vocabulary limit. Real traffic includes prosigns, numbers, and call signs that do not spell PARIS. Still, when someone says “I copy at eighteen WPM,” they mean eighteen PARIS-length words per minute if everyone uses the same ITU ratios.
Farnsworth spacing in practice
Farnsworth training sends characters at a target speed but inserts extra silence between letters (and often between words). Character speed might stay at 20 WPM while effective text speed feels like 10 WPM because the gaps grew. The math is simple: add the extra gap time to the PARIS count when you estimate how fast a passage feels.
On MorseCoder, Farnsworth presets on the homepage translator lengthen inter-letter gaps without shrinking dashes. That matches how many instructors teach: hear full letter shapes early, then compress gaps as accuracy improves. Our dedicated Farnsworth spacing guide walks through when to widen gaps and when to raise plain WPM instead.
Do not confuse Farnsworth with “slow code” that drags every dit. Slow dits change the sound of letters and no longer match on-air CW. If lesson material feels fast, widen gaps first; only lower character WPM when fatigue or equipment limits demand it.
From units to milliseconds
Once you know unit count for a letter, multiply by 1200/WPM to estimate milliseconds. Example: letter Q (--.-) totals thirteen units (3+1+3+1+1+1+3). At 20 WPM that is roughly 13×60 ≈ 780 ms of keyed time excluding the mandatory three-unit letter space that follows.
Word gaps use seven units. After PARIS at 20 WPM, the inter-word pause is about 7×60 = 420 ms. Letter gaps use three units. Building these numbers into your expectations helps when you compare software sidetone to a straight key or paddle.
Use the live table below to explore WPM values. Each row recomputes dot milliseconds and sample letter lengths using the same formulas the letter guides reference.
How to drill timing on MorseCoder
Start on the translator at a fixed WPM with Farnsworth off. Send a single letter, pause, send another, and listen for equal intra-letter gaps. Move to trainer modules that quiz isolated characters, then short words.
Open any letter guide and read the “At a glance” row for length at 20 WPM. Compare what you hear with the computed milliseconds. When decoding unspaced Morse, timing ambiguity is separate from speed; see decode without spaces for how splits change readings.
Licensed operating still requires on-air practice. ITU defines timing; clubs and nets provide real QRM and pacing. Use this page to align your ear with the standard before you judge live copy.
Common timing mistakes
Inserting a letter space inside a character turns one symbol into two. Decoders then print garbage or # markers. Fix spacing before you raise WPM.
Counting dots aloud during a QSO is normal for beginners but becomes a ceiling near fifteen WPM. Farnsworth exists to keep shapes fast while you build automatic recognition.
Assuming American Morse timings match ITU International Morse. Railroad Morse used different rules; this site implements ITU International Morse per M.1677-1.
Ignoring word gaps when sending phrases like SOS. Operators send SOS as one prosign rhythm; learners typing SOS should still understand the three-letter structure and the seven-unit word gap that follows a complete word in text traffic.
Sources and further reading
Primary timing ratios: ITU-R M.1677-1. Abbreviations and operating signals: ITU-R M.1172. Amateur training context: ARRL Learning Morse Code. Overview article: Wikipedia — Morse code. On-site deep dive: words per minute blog and Farnsworth vs Koch.