How Morse code works
Morse code sends letters as patterns of short and long signals, called dots and dashes, or dits and dahs when you say them out loud. It was developed in the 1830s and 1840s for the electric telegraph, and the international version used today was agreed in 1865. Radio amateurs still use it every day, because a simple Morse signal gets through when voice can't.
The timing is what makes it work, and everything is measured in dots:
| Part | Length |
|---|---|
| Dot | 1 unit |
| Dash | 3 units |
| Gap between dots and dashes in a letter | 1 unit |
| Gap between letters | 3 units |
| Gap between words | 7 units |
Speed is measured in words per minute using the word PARIS, which is exactly 50 units long. At 20 wpm a dot lasts 60 milliseconds, and in general a dot lasts 1,200 divided by the speed in milliseconds.
Learning with Farnsworth spacing
If you learn Morse slowly, you end up counting dots and dashes instead of hearing each letter as a sound. Farnsworth timing fixes that. Each letter is sent at a normal speed, such as 18 wpm, but with extra space between letters and words so the overall speed is slower, such as 8 wpm. As you improve, you reduce the extra spacing. Set the spacing speed above lower than the speed to try it. The calculator uses the ARRL's Farnsworth timing formula.
How the audio decoder works
The decoder looks for the strongest steady tone in your recording, then measures how loud that tone is every 5 milliseconds. It sets a threshold halfway between the background noise and the signal, and marks each stretch above it as a beep. It sorts the beeps into dots and dashes by length, and the gaps into letter and word breaks, then looks up each pattern in the Morse table. Characters it can't match show as #.
It reads clean, steady Morse very reliably, including computer-generated practice files and strong signals off air. Hand-sent Morse with uneven timing works too, because the decoder follows changes in speed, but you'll see more mistakes. Very weak signals, fading, interference and two signals at once are hard for any automatic decoder. If you know the tone frequency, setting it by hand helps a lot when there's more than one signal.
Common Morse you'll hear
- CQ (–·–· ––·–) means "calling any station".
- DE means "from", as in CQ DE M0ABC.
- K means "over", inviting a reply.
- SOS (···–––···) is the distress signal, sent as one continuous pattern with no gaps between the letters.
- 73 means "best regards" and ends most friendly contacts. See the Q codes page for more.
Questions
How do I decode Morse code from an audio file?
Choose your audio file above or drop it on the page. The decoder finds the tone, works out the speed and shows the text, with a picture of the signal so you can check each letter. Nothing is uploaded, because everything runs in your browser.
Can I download Morse code as an audio file?
Yes. Type your text, choose the speed and tone, and press Download WAV. The file plays on any phone or computer.
How do you say hello in Morse code?
HELLO is ···· · ·–·· ·–·· –––. Type any word into the translator to see and hear it.
Can I print a Morse code chart?
Yes. Press Print this chart under the chart, and the page prints just the chart and the tables, without the menus.
What is SOS in Morse code?
··· ––– ··· (three dots, three dashes, three dots), sent as one continuous signal without letter gaps. It was chosen because it's easy to send and recognise, not because it stands for anything.
Why does the decoder get some letters wrong?
Usually because of noise, fading, another signal on a nearby frequency, or uneven hand-sent timing. Try setting the tone frequency and speed by hand in the decoder settings, or trim the recording to just the Morse.
Is my audio uploaded anywhere?
No. Files and microphone audio are processed entirely in your browser and never leave your device.