Help size.illusions.im grow
No ads, no cookies, no paywall. Just a small, hand-built site and an eraser with a ruler.
A little support goes a long way
This site is hand-built, fact-checked and free to use. If a game, an experiment or one of Useless’s notes made you look twice, a little support keeps it going and helps the network grow.
Size illusion printables
Fact-checked PDFs in A4 and US Letter, sold as instant downloads from the ReallyByte store.
Draw Your Own Size Illusions: Step-by-Step Sheets
Ten classic size illusions to draw with a ruler and compass, from the Müller-Lyer arrows to the Ponzo railway, each with measured steps, a practice grid and the trick explained
Size Illusion Puzzle Pack: Measure, Spot & Solve
Guess-then-measure challenges, “which is bigger?” puzzles, a maze, a word search and a crossword, all with answer keys
Make-and-Test Size Illusion Experiment Cards
Twelve experiment cards for the kitchen table or the classroom: the coin test, the moon trace, a shoebox peep-show and more, each with what to look for and why
Illusion Lab Log: Measure-It Record Book
Record your guesses and your measurements, work out your error, test friends and family, and keep a moon diary
Don’t Trust Your Eyes! Kids’ Size Illusion Worksheets
For ages 6 to 11: guess and measure, spot the trick, draw an illusion, illusion maths, a maze and colouring, with answer keys
Classic Size Illusions Poster Set
Six fact-checked posters: Müller-Lyer, Ebbinghaus, Ponzo, the moon illusion, the Ames room and the T illusion
Best valueThe Complete Size Illusions Printables Bundle
All six packs plus a guide, A4 and US Letter, in one download.