Numbers in Morse Code

All ten digits are exactly five elements long, and they follow one rule, which means you can work any of them out instead of memorising ten separate codes.

The rule

Start at 1, which is .----: one dot, then dashes to fill five. Each digit after it turns one more dot on, from the left. By 5 you have....., all dots. Then the dashes come back from the left, and 0 is -----, all dashes.

So the count of leading dots is the digit, up to 5; after that the count of leading dashes is the digit minus 5. Nothing to memorise.

Why five, and what it costs

The letters were assigned by frequency, so the common ones are short: E is a single dot. The digits got no such treatment. Every one is five elements, which makes them perfectly regular and, taken together, the slowest characters in the alphabet. At twenty words a minute a 0 takes 1.14 seconds where an E takes0.06; the ten digits sent in a row take 10.0seconds, which is longer than most words of the same length.

The regularity is the point. A text is mostly letters, so the alphabet is optimised for letters and the digits are a small tax. But it also means a digit can never be mistaken for another digit by a dropped element the way S and H can: the count is always five, and a four-element run is a letter by definition. What a digit can be mistaken for is the letter one element shorter, so 5 and H, or 0 and the all-dash run, are worth a moment's attention.

Cut numbers

Operators in a hurry shorten the digits by dropping the run of dashes from one end, which turns each into a letter: 1 keeps its front and becomes A, 7 keeps its back and becomes B, 0 becomes a single T. It is a convention between people who have agreed it, common in contests and never in the standard, and it only works because the letter's code is one end of the digit's. Each pair below is checked against the code table when this page is built.

4, 5 and 6 have no useful cut: 5 would become E, which is too short to be safe, and 4 and 6 have no letter as a prefix that is not already a digit. Do not send cut numbers to a stranger. They will read a serial number as a word.

Where digits turn up

Callsigns, so every amateur learns them early; frequencies and signal reports; and the two-digit codes that amateurs use as words. 73 is "best regards" and closes most contacts; 88 is "love and kisses" and is used more than you would expect. Sent as digits, both are ten elements plus a gap, and both are so common on the air that operators hear them as a single shape rather than two numbers.

Hear any number

Frequently asked

Why is every number five elements long?

Letters were assigned short codes by how often they appear in English, so E is one dot. Digits got no such treatment, they are all five elements, which makes them slower to send but completely regular.

Are there shorter versions?

Yes, though not in the standard. Amateur operators use abbreviated "cut numbers" in contests, T for 0 and N for 9, for instance, because sending five elements ten times over gets slow. They are a convention between operators, not something you should expect a stranger to understand.