What is on the sheet
Two wheels. The big outer wheel carries the alphabet as you write it. The smaller inner wheel carries it again, with a number under each letter from 0 to 25: that number is the shift. Beside them are the steps to make and use it, and a message in Caesar's own shift of 3 to crack, with the answer printed upside down.
How to make it
Print at 100% on card stock if you have it; plain paper works but wears faster. Cut out both wheels on the dark outer line. Lay the small wheel on the big one with the center marks together, push a brad (a paper fastener) through both, and open its legs at the back. A thumbtack into a cork board does the job too, or a pencil point if you only need it once.
How to use it
Turn the inner wheel until the letter you want sits under the outer A. With D under A, that's a shift of 3, and the small number under D says so. To encode, find each letter of your message on the outer wheel and write down the letter under it: A becomes D, B becomes E. To decode, find each secret letter on the inner wheel and read the letter above it.
Don't know the shift? Try them in turn: there are only 25, which is why a Caesar cipher is a puzzle and not a lock. The Caesar cipher translator does the turning for you, and shows the whole shifted alphabet for any key.
Frequently asked questions
How do you make a Caesar cipher wheel?
Print the two wheels, cut each out on its outer line, and pin the small one on top of the big one through the center marks with a brad, so the inner wheel turns. Card stock lasts longest.
How do you use a cipher wheel?
Turn the inner wheel so a letter sits under the outer A; the number under it is the shift. To encode, find each letter on the outer wheel and write the inner letter under it. To decode, go from inner to outer.
What shift did Julius Caesar use?
Three, according to the Roman historian Suetonius: A was written as D, B as E, and so on.
How do you crack a Caesar cipher without the key?
Try every shift. There are only 25, so turning the wheel through each one until the message reads as words takes a few minutes at most.
What do I need besides the printout?
Scissors and something for the middle: a brad (paper fastener) is best, and a thumbtack into cork works too.
Covert Mail on your phone
Covert Mail teaches the Caesar cipher and fourteen other codes a few letters at a time, and its cipher desk encodes a message to send to a friend. It's free on the App Store.
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The secret code worksheet has room to write out the message, and the pigpen cipher key is another code to try. There's more on the printables page.