How Morse code works — timing rules explained simply

Every Morse code tutorial explains dits and dahs. Almost none explain the timing rules that make Morse actually work as a communication system. Get the ratios wrong and even a technically correct pattern reads as garbage. Get them right and a five-watt radio signal will punch through noise that swallows a hundred-watt voice call.

Here is how it actually works, at the level you need to understand it — not the level a textbook writes it at.

Morse code is timing, not symbols

The most common misconception: people think Morse is . and -. It is not. Those are just how we write it on paper. What the actual Morse signal transmits is a key held down for a specific duration, then released. A radio operator’s fist, a flashlight switch, an audio oscillator gated by a computer — all Morse produces is regular on-off patterns of a single reference length.

Every symbol, every letter, every gap in Morse is measured against one basic unit. Everything else is a multiple.

The five timing rules

That is the whole specification. Those five numbers define every Morse code transmission ever sent.

Get one of them wrong and the letter changes. If you send . - (di-dah = A) but leave a 3-unit gap in the middle instead of 1 unit, you have sent . then - — E then T. Two letters, not one. That is why timing matters more than pattern memorisation for anyone learning to send.

What is a “unit” — the WPM speed math

The unit length is not fixed. It depends on how fast you are sending.

• At 5 WPM, one unit is 240 ms.
• At 13 WPM, one unit is 92 ms.
• At 20 WPM, one unit is 60 ms.
• At 40 WPM, one unit is 30 ms.

The formula is:

unit_length_ms = 1200 / WPM

Where does 1200 come from? From the reference word PARIS. The word PARIS sent with a single word gap at the end totals exactly 50 units of ON and OFF time. So one minute at N words per minute = 50 × N units. Divide 60,000 milliseconds by that, and you get 1200/WPM per unit. This is the standard used by every modern Morse trainer, contest scoring software, and radio’s CW filter.

You can check it. At 20 WPM the unit is 60 ms. Word PARIS = 50 units × 60 ms = 3000 ms = 3 seconds. Twenty of those per minute. Math checks out.

Farnsworth spacing — the trick that lets beginners survive

There is one problem with the standard timing. At 20 WPM, the letter K (-.-) takes about 600 ms end to end. Then a 180 ms letter gap. Then the next letter starts. For a beginner, 780 ms is not enough time to identify K, write it down, and prepare for what comes next.

The Farnsworth modification, invented in the 1950s, is elegant: keep each character at full speed, but widen the gaps between them. So the individual K still sounds like a 20 WPM K — which is what your ear needs to train on — but the gap before the next letter stretches out. A beginner might practice with 20 WPM characters and 8 WPM effective text speed, giving 400+ ms of thinking room between letters.

This is why the “speed” slider in a good Morse trainer has two values, not one: character speed (always fast, never below 15 WPM for real training) and text speed (adjustable to the learner’s current level).

Our in-depth Koch method walkthrough covers why full-speed characters matter and how Farnsworth makes the ramp humane.

The PARIS reference is arbitrary — sort of

Why PARIS and not HELLO? Because when the standard was chosen in the mid-20th century, PARIS was picked as a word whose Morse timing added up to a nice round 50 units, which made the WPM math clean. HELLO would give a different total and you would have to divide by weird numbers.

• H = ···· = 7 units (4 dits + 3 inter-symbol gaps)
• E = · = 1 unit
• L = ·—·· = 9 units
• L = 9 units
• O = ——— = 11 units
• Letter gaps: 4 × 3 units = 12
• Word gap: 7 units
• Total: 56 units

56 doesn’t divide as cleanly into 60000 as 50 does. That is the entire reason PARIS won. There is nothing special about the letters themselves — the arbitrary math is why every contest and trainer standardises on it.

What a Morse signal actually looks like

Suppose you send SOS at 15 WPM. Unit = 80 ms.

S: dit dit dit  →  80 ON, 80 OFF, 80 ON, 80 OFF, 80 ON
   letter gap  →  240 OFF (3 units)
O: dah dah dah  →  240 ON, 80 OFF, 240 ON, 80 OFF, 240 ON
   letter gap  →  240 OFF
S: dit dit dit  →  80 ON, 80 OFF, 80 ON, 80 OFF, 80 ON

Total: about 2.16 seconds.

Except SOS is a prosign — three letters run together with no letter gaps. Same three-symbol groups (three shorts, three longs, three shorts), but transmitted as one continuous nine-symbol shape. That is the trick that makes SOS unmistakable. Read more in our SOS post.

Prosigns — the timing rule that only applies to procedural signals

Every Morse operator uses a small set of patterns that aren’t letters at all. They’re called prosigns — short for “procedural signals” — and they carry operational meaning: “over to you”, “paragraph break”, “end of contact”, “distress”. The most famous one is SOS.

What makes a prosign different from a normal string of letters is a single timing rule: prosigns have no letter gap. All the dits and dahs run together as one continuous shape.

Take the SOS distress signal. Sent as three normal letters S, O, S with standard 3-unit letter gaps, it’s three separate letters totalling around 15 units of ON plus 6 units of gap. Sent as the prosign <SOS> — one continuous nine-symbol pattern with no letter gaps — the same dit-dah content collapses to about 15 units of ON plus 2 units of intra-symbol gap. That’s roughly 30% shorter on the wire, and much harder to mishear as any other Morse sequence.

Here are the prosigns you will run into on the air, along with their patterns:

Written notation traditionally uses an overline (e.g. AR with a bar on top). In plain text you’ll see them as <AR> or [AR]. Same shape either way.

If you want to hear how a proper prosign sounds versus the letter-by-letter mistake most tutorials teach, drop <SOS> into our Morse audio translator and listen back at 15 WPM — the difference is immediately obvious. Full history of the SOS prosign is on our SOS post.

Contest speeds and what “fast” actually means

• Beginner recognition: 5-10 WPM effective text speed, 15-18 WPM character speed with Farnsworth.
• Conversational ham radio (typical QSO): 15-20 WPM.
• CW Sprint / NAQP / other short-form contests: 25-30 WPM.
• CQ WPX, CQWW, contest top-tier: 30-40 WPM head-copy.
• Superhuman: 50+ WPM head-copy. A handful of operators on Earth can do this. Al Boecker, W7NR, famously copied 75 WPM in the 1960s.

The gap between “beginner” and “operator” is 15-20 WPM of text speed and about six to twelve months of daily practice. The gap between “operator” and “contest top” is another 10 WPM and years of dedicated speed drills. There is no shortcut past either.

The full week-by-week breakdown of learning Morse covers what happens after phase one.

Sending vs receiving

The timing rules apply to both, but the emphasis flips.

Sending (with a straight key, paddle, or software): the operator has to produce exact ratios. Sloppy sending is called “poor fist” and is why many hams struggle to be understood even when their sending speed is fine.

Receiving: the listener has to recognise ratios that are already there. This is where 90% of a beginner’s practice time goes, because your ear needs hundreds of exposures before dit vs dah becomes automatic.

You can practice sending on any device with a button — your phone screen, a Bluetooth key, or a real paddle. But if you want to actually copy Morse fluently, focus 80% of your time on receiving.

Why this all still matters

Voice replaced Morse for civilian maritime distress in 1999. Amateur radio dropped the Morse licence requirement in the US in 2007. Every year someone writes “Morse code is dead.”

They are wrong for a specific technical reason. Timing-based signalling survives conditions that voice cannot. A Morse signal at -10 dB signal-to-noise ratio is still readable if you can hear one dit through the static. Voice becomes unintelligible at 0 dB. That is a 10× difference in signal power for the same range.

Ham radio operators making 5-watt “QRP” contacts across oceans on 20-meter CW know this. Aviation pilots hearing their NDB navigation ident on a scratchy audio channel know this. The military and emergency services that keep Morse in the backup toolkit know this.

Morse is not the fastest way to send text. It is the way that works when nothing else does. Understanding the timing is understanding why it survives.

Learn to actually copy Morse

If you have made it this far you understand Morse timing as well as most amateur operators do on day one. What is left is the physical part — training your ear to catch dit-dah patterns as whole shapes, not counted symbols.

That takes daily practice at real character speed. Our ten-minutes-a-day 21-day plan walks you through it. The audio-training method Ludwig Koch invented explains why full-speed exposure works when slow-and-accelerate fails.

If you just want to hear Morse at any speed you type into a box, our browser-based Morse translator with adjustable WPM plays back whatever text you give it. Good for a taste before you commit.

FAQ

What is the standard Morse code speed?

There isn’t one. 13 WPM was the historic threshold for the old US amateur radio licence, so it stuck as an informal “conversational” reference. In practice ham radio CW happens anywhere between 15 and 30 WPM depending on the operators.

What is one “unit” in Morse code?

Whatever length keeps the timing ratios correct at your chosen WPM. Formula: 1200 / WPM in milliseconds. At 20 WPM, one unit is 60 ms.

Why is PARIS the reference word?

Because its Morse timing at standard ratios sums to exactly 50 units, which makes the WPM math clean. If you send PARIS N times in one minute, you are sending N words per minute.

What is Farnsworth timing?

A modification of standard timing that keeps individual characters at full speed but widens the gaps between them, giving beginners more thinking room. Every good Koch-method trainer uses it.

Can I change the Morse audio frequency?

Yes. The standard is 600-750 Hz sine tone. Higher frequencies (900-1000 Hz) work but tire the ear faster. Lower (below 500 Hz) get muddy on cheap headphones.

Are dots and dashes the same thing as dits and dahs?

Yes — same thing, different vocabulary. “Dot” and “dash” are the written-notation names. “Dit” and “dah” are the spoken/heard names, and they are what CW operators actually use because you can say dit-dah in Morse timing and it sounds like the letter A (which is what it spells). Nobody says “dot dash” at 20 WPM.