Morse code alphabet
O in Morse Code
The letter O in Morse code is --- — spoken "dah-dah-dah". Press play to hear it, flash it as light, or copy the code.
What does --- mean in Morse code?
--- is the letter O in International Morse code. The code is made of 0 dits (short) and 3 dahs (long), which is why it is read aloud as "dah-dah-dah". It takes 11 time units to send — at a standard 20 words per minute that is roughly 660 milliseconds.
O is the middle of SOS (··· −−− ···). Three dahs make it one of the longest-sounding letters in time even though it is only three symbols — each dah lasts as long as three dits.
How O is timed
Morse timing is built from one unit — the length of a dit. A dah is three units, and there is one silent unit between the symbols of a letter. Here is O drawn to scale:
How to remember O
Say the phrase OH MY GOD to the rhythm of the code — the stressed syllables are the dahs, the rest are dits. Hear it a few times with the player above and the phrase will come back by itself.
Easy to confuse with
When you are learning by ear, these codes sound close to O:
Words that start with O
O at a glance
| Morse code | --- |
|---|---|
| Spoken | dah-dah-dah |
| Symbols | 0 dits, 3 dahs |
| Length | 11 units · ≈660 ms at 20 WPM |
| NATO phonetic | Oscar |
| Frequency in English | ≈7.5% — #4 of 26 letters |
| Position in alphabet | 15 of 26 |
| Reversed | same code backwards (palindrome) |
Frequently asked questions
How do you write O in Morse code?
The letter O is written --- — 0 dits and 3 dahs. Spoken aloud it is "dah-dah-dah".
What does --- mean in Morse code?
--- is the letter O O in International Morse code. If you see or hear "dah dah dah", it stands for O.How long does O take to send?
O lasts 11 time units (a dit is 1 unit, a dah is 3, with 1 unit between symbols). At 20 WPM that is about 660 ms; at a beginner speed of 12 WPM about 1100 ms — plus a 3-unit pause before the next character.
What is the NATO phonetic word for O?
In the NATO phonetic alphabet O is "Oscar". Radio operators often say the word and then send --- so the letter cannot be misheard.