Morse Code Explained: Timing Rules

Every Morse letter is built from one unit of time.

The ITU's international standard sets the rules: a dash is three dots long, letters are three dots apart and words seven. Get the rhythm right and the code reads itself.

Updated 14 October 2026 · 5 sources

Dot is one unit
Dash is three
Words are seven apart
Timing is the whole code

Check the timing

THE SHORT ANSWER

Morse is timing,
not just dots.

Letters, numbers and punctuation
are all made of the same two signals and three gaps.

THE STANDARD

One code for everyone

International Morse code is confirmed by the ITU in Recommendation ITU-R M.1677-1, approved in 2009. It notes the code has been in use since 1844.

How it began

THE RHYTHM

Three lengths of gap

Signals inside a letter are one dot apart, letters three dots apart and words seven dots apart. The gaps carry as much meaning as the signals.

Check the timing

AT SEA

The call everyone knows

The first International Radiotelegraph Conference in 1906 established SOS in Morse code as the international maritime distress signal, the ITU says.

See the dates

A ship's signal lamp mounted on a deck railing at dusk, with a calm grey sea and horizon behind it — AI-generated image, not a photograph of a real person or place.

FOUR THINGS THAT HELP IT CLICK

Hear the shapes,
not the symbols.

Morse code makes more sense once you know why it is built the way it is. These facts come from the ITU standard and the University of Cambridge's NRICH project.

Common letters are short
NRICH explains that the most frequent letter, e, was given the shortest code, a single dot, which is why Morse is not in alphabetical order.
SOS is three, three, three
The distress signal is three dots, three dashes and three dots.
Speed is counted in words
The word PARIS with its trailing space equals 50 units, the standard word length. NRICH says experienced operators work at 20 to 30 words per minute.
Operators have their own signals
The ITU lists procedure signals too: eight dots means error, and a starting signal precedes every transmission.

TWO DATES WORTH KNOWING

From a wire
to the open sea.

One date for the first message,
one for the distress call that went global.

1844

Washington to Baltimore by telegraph

The Library of Congress records that the first message was sent on 24 May 1844 from the US Capitol in Washington to Baltimore. The ITU standard also dates Morse code's use from 1844.

FIRST MESSAGE · LIBRARY OF CONGRESS

1906

SOS adopted for ships at sea

The ITU says the first International Radiotelegraph Conference in 1906 established SOS in Morse code as the international maritime distress signal. In 1912, after the Titanic sank, a conference agreed a common frequency for ships' distress signals.

DISTRESS SIGNAL · ITU

NRICH, part of the University of Cambridge's Millennium Mathematics Project, notes that a Berlin conference in 1851 set the international standard that differed from the original American code.

THE TIMING RULES

How long is
each part?

Pick a part of a Morse message to see how long it lasts, measured in dots. The bar shows how long it is compared with the longest gap.

Lengths from Recommendation ITU-R M.1677-1, International Morse code, Annex 1, Part I.

Timing check

Choose a partA dotA dashGap inside a letterGap between lettersGap between words

A dot1 unit

The basic unit. Every other length in Morse code is measured in dots, so the speed of the dot sets the speed of the whole message.

A dash3 dots

The ITU standard says a dash is equal to three dots. A dash that is too short starts to sound like a dot.

Gap inside a letter1 dot

The space between the signals forming the same letter is equal to one dot, which keeps a letter's signals running together.

Gap between letters3 dots

The space between two letters is equal to three dots. It tells the listener one letter has ended and the next is starting.

Gap between words7 dots

The space between two words is equal to seven dots, the longest pause in the code.

Source: Recommendation ITU-R M.1677-1 (10/2009), International Morse code.

A hand resting on a modern Morse key next to a radio receiver on a tidy desk, seen from the side — AI-generated image, not a photograph of a real person or place.

HOW IT BEGAN

Current through a wire,
a click at the end.

The early telegraph sent an electric current along a wire to an electromagnet at the far end, which pulled a metal key down with a click. How long the sender held the key decided whether a dot or a dash arrived, the US National High Magnetic Field Laboratory explains.

The Library of Congress says the first system printed raised dots and dashes on paper tape, but clerks learned to read messages by sound. The ITU notes the code is still used in amateur and amateur-satellite radio, and to a diminishing extent in the mobile and fixed services.

In conversation

Questions people ask

How long is a dash in Morse code?

Recommendation ITU-R M.1677-1 says a dash is equal to three dots. The gap between letters is also three dots, and the gap between words is seven.

Why is E just one dot?

NRICH explains that the code's designer counted printer's type and found more e's than any other letter, so e was given the shortest code.

When did SOS become the distress signal?

The ITU says the first International Radiotelegraph Conference, in 1906, established SOS in Morse code as the international maritime distress signal.

Is Morse code still used?

Yes. The ITU standard says it continues to be used in the amateur and amateur-satellite services, and to a diminishing extent in the mobile and fixed services.

Is there a Morse sign for @?

Yes. The ITU standard includes the commercial at, written as dot dash dash dot dash dot.

Sources

Each figure on this page comes from the sources below.

Rhythm you
can read.