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Semaphore Flags
Type a word and see how a signaller would send it with two semaphore flags. The full semaphore flags alphabet is below, drawn as you would see the signaller facing you.
Semaphore flags alphabet
Each letter is one pose: the two arms point in two of eight directions, like the hands of a clock. The chart shows every letter, the numerals sign and the annul (cancel) sign.
Arm positions for every letter
Directions are as you see them, facing the signaller. "Low" is halfway between down and straight out; "high" is halfway between straight out and up.
| Sign | One arm | Other arm |
|---|---|---|
| A / 1 | down | low left |
| B / 2 | down | left |
| C / 3 | down | high left |
| D / 4 | down | up |
| E / 5 | down | high right |
| F / 6 | down | right |
| G / 7 | down | low right |
| H / 8 | low left | left |
| I / 9 | low left | high left |
| J (also: letters follow) | up | right |
| K / 0 | low left | up |
| L | low left | high right |
| M | low left | right |
| N | low left | low right |
| O | left | high left |
| P | left | up |
| Q | left | high right |
| R | left | right |
| S | left | low right |
| T | high left | up |
| U | high left | high right |
| V | up | low right |
| W | high right | right |
| X | high right | low right |
| Y | high left | right |
| Z | right | low right |
| Numerals sign | up | high right |
| Annul (cancel) | high left | low right |
How semaphore works
Flag semaphore sends letters by sight. The signaller holds a flag in each hand and moves the arms between eight positions; each pair of positions is a letter. At sea the flags are red and yellow, divided diagonally; on land, white and blue flags are often used so they stand out against the ground. Semaphore was developed in the early 1800s from the earlier mechanical semaphore towers, and navies still teach it for silent ship-to-ship signalling.
The letters follow a pattern. A to G keep one arm down and move the other arm around the circle. H to N keep one arm low and move the other, then O to S keep one arm straight out, and so on. Once you see the circles, the semaphore alphabet is easy to remember.
Numbers in semaphore
Numbers reuse the first ten letters: A = 1, B = 2 … I = 9 and K = 0. To show that numbers follow, the signaller first sends the numerals sign (one arm up, the other high right as you see it). The J sign switches back to letters. The tool above adds both signs for you, so "Room 12" becomes R, O, O, M, the numerals sign, A and B.
Using this as a semaphore flags translator
- Letters A–Z, numbers and spaces are shown; punctuation is skipped.
- Save the picture to print a signal card, a scout badge sheet or a party sign.
- Practise in a mirror: your view of yourself is reversed, so the chart's left becomes your right.
How we tested
We checked the arm positions for all 26 letters, the numerals sign and the annul sign against the semaphore chart of the Australian National Botanic Gardens flags pages. Everything matched except I: that chart gives I the same two positions as K, so we follow the regular pattern of the alphabet (one arm low, the other high, on the same side). "Room 12" gave R, O, O, M, the numerals sign, A and B, and words stay on one line when they fit. We saved it as an image (840 × 572 px) and looked at it. We ran the page in Chromium at desktop width and at 375 px: no sideways scrolling and no console errors. Not tested yet: Safari on iPhone and Firefox.
Questions
What do semaphore flags look like?
Two square flags on short poles. At sea each flag is divided diagonally into red and yellow; on land, flags divided into white and blue are common.
Is the chart drawn from the signaller's side or the viewer's side?
From the viewer's side: you are facing the signaller. A is shown with one arm down and the other low on your left, which is the signaller's right arm.
How do you send numbers in semaphore?
Send the numerals sign first, then the letters A to I for 1 to 9 and K for 0. Send J to go back to letters.
What does the annul sign mean?
It cancels the last signal, so the receiver ignores it. It is one arm low on your right and the other high on your left.