Dit to dah ratio and weighting in Morse code

27 October 2026 · 7 min read

The standard dit to dah ratio in Morse code is 1 to 3: a dah lasts exactly three times as long as a dit, and the silence between the dits and dahs of one character lasts one dit. Weighting is a keyer setting that makes the tones a little longer or shorter compared with the silences between them, while the speed stays the same. Most of the time you want exactly the standard; drift far from it and letters start to turn into other letters.

The 1 to 3 standard, and why it holds up

The international standard for Morse (ITU-R M.1677-1) sets every length in dots, its word for dits: a dash (a dah) is equal to three dots, the space between the signals of one letter is one dot, the space between letters three, the space between words seven. Nothing in it is in milliseconds. That matters, because no listener measures milliseconds either. Your ear, or a decoder, tells a dit from a dah by comparing lengths against each other.

The 1 to 3 ratio leaves plenty of room for that comparison. A dit is 1 unit and a dah 3, so the dividing line sits around 2 units, a full unit away from each. A dit can stretch a fair way, or a dah shrink, before one is mistaken for the other. Squeeze the ratio to 1 to 2 and that margin halves. Squeeze it further and the difference is gone.

When it goes, mixed letters collapse into all-dit or all-dah letters:

You meant	Code	Dahs too short, heard as	Dits too long, heard as
A	`.-`	I `..`	M `--`
N	`-.`	I `..`	M `--`
U	`..-`	S `...`	O `---`
W	`.--`	S `...`	O `---`

Those are the extremes. The milder cases on the way are what make a fist hard to copy: the receiver keeps hesitating over each element.

What weighting is

With paddles and an electronic keyer, the keyer times every element for you at the speed you set. Weighting, as the word is generally used, changes how each element’s time is split between tone and silence:

Heavier weighting: longer tones, shorter silences between the elements.
Lighter weighting: shorter tones, longer silences between them.

The speed stays the same because whatever is added to a tone is taken out of the silence after it. A dit plus its following space still lasts 2 units; it is just divided differently.

Keyers do not all name, show or work out these settings the same way, and some can set the dah to dit ratio directly as well; the keyer’s manual says what its normal setting is. Weighting can make up for equipment that shortens or lengthens each element on its way to the air, and some operators set it by ear for a sound they prefer. A learner needs none of it.

What weighting does to the ratio

If weighting adds the same time to every element, dits and dahs alike, it changes the apparent ratio too. Add a fifth of a unit:

The dit becomes 1.2 units of tone and 0.8 of silence.
The dah becomes 3.2 units of tone and 0.8 of silence.
The dah is now 3.2 ÷ 1.2, about 2.7 times the dit, instead of 3.

Take a fifth of a unit away instead and the dit becomes 0.8, the dah 2.8, and the ratio about 3.5. Done that way, heavy weighting narrows the contrast between dits and dahs, and light weighting widens it, even though nothing set the ratio itself.

Why heavy or light weighting sounds odd

Your ear learned each character as a shape with fixed proportions: tones of 1 and 3, silences of 1 inside. Weighting bends that shape.

Heavy weighting shortens the silences inside a character. A little tends to sound full and solid. Too much and the dits can start to run together: H, ...., and 5, ....., lose their clear count and sound more like a buzz with ripples in it, and telling S from H from 5 takes work.

Light weighting clips the tones and opens the silences. A little tends to sound crisp. Too much tends to sound choppy, and the silences inside a character grow toward the length of a gap between characters. Then a letter can start to sound like two: P, .--., can come out as A and N, .- -..

As a rule of thumb, a little of either changes the feel of a signal more than its readability, while a lot, or weighting on top of an uneven fist, makes it harder to copy. While you learn, leave it at normal.

Why a straight-key fist drifts

On a straight key you are the timer, and nothing holds you to 1 to 3 except your own sense of rhythm. A hand-sent signal always varies a little, and that variation is part of what makes a fist recognizable. The trouble is when it drifts in one direction. These are the drifts worth listening for:

Dahs that shrink as you speed up. A hurried or tired hand tends to cut the dah short, and the ratio slides from 1 to 3 toward 1 to 2. Listen for this one first; the table above shows where it leads.
Heavy dits. Holding the key a fraction too long on every dit lengthens them toward the dahs. It is an easy habit at slow speeds, where a dit is a long 240 ms at 5 WPM and can feel as if it ought to be held.
Stretched gaps inside a letter. If you pause to think of the next element, the inside gap grows and the letter can split.
A fist that loosens over a long message, as the hand tires.

How a key is adjusted changes how it feels under your hand (spring tension and contact gap), but the ratio itself lives in your hand and your ear.

How to hear your own ratio

You cannot judge your ratio while you send. These checks work with any key, or with a pencil tapped on a desk and a phone recording it:

Record yourself, then listen beside a reference. Play Morse sent by a machine at the same speed, then your recording. Clipped dahs and fat dits stand out against a correct signal.
Send letters that test the ratio. A and N, U and D, V ...- and B -... each mix dits and dahs, so any drift is audible. Send them slowly, saying the rhythm in your head: di-dah for A, dah-dit for N, di-di-di-dah for V, dah-di-di-dit for B.
Compare the figures 5 and 0. The 5, ....., is 9 units long; the 0, -----, is 19. A correct 0 lasts a little more than twice as long as a 5. If your 0 sounds barely longer, your dahs are short.
Look at it. Open the recording in an audio editor and zoom in: tones show as blocks you can measure in milliseconds. Measure several dits and dahs, not one, and see whether the dahs come out near three times the dits. How long is a dit? has the target lengths at every speed.
Let a decoder read it. If it prints I for your A, or S for your U, the ratio is the problem; if it splits or merges letters, the gaps are.

A simple fix for a short dah is to slow down and lean on it. Send a page of A, N, U and D at a speed where you can make every dah generously long, then bring the speed back up a step at a time, recording as you go. Your fist in Morse code has more on building an even hand.

If you key on a Mac, Dot & Dash gives you a version of check 4 after every letter in a lesson: it draws each dit and dah you keyed against the length it should have been, marks the ones that were too short or too long, and shows the speed you keyed at. With the straight key it follows your own pace, learning the length of your dit as you key.

Questions

Is a dah always exactly three dits?

In the standard, yes: the ITU standard says a dash, or dah, is equal to three dots. In practice a hand-sent dah varies a little, and keyer weighting or ratio settings can move it, but 1 to 3 is the reference everyone is measured against.

What does heavier weighting mean on a keyer?

It usually means each tone is a little longer and the silence after it a little shorter, by the same amount, so the speed does not change. A little tends to sound full; too much can make dits run together.

Should a beginner change the weighting?

No. Leave it at the keyer’s normal setting while you learn, so your ear is trained on standard proportions. Weighting is for adjusting to equipment or taste once your copying is solid.

How can I tell if my dahs are too short?

Record yourself and compare with machine-sent Morse at the same speed, or let a decoder read you. If A comes out as I, or your 0 sounds barely longer than your 5, your dahs are short.