Resize one object until it looks as tall as the thing beside it. Lock it in, and the real measurements appear.
A size comparison game round: Eiffel Tower is drawn at its true size, and Statue of Liberty is drawn at the size you set.
Rounds 0Average score —Best —
A size comparison game puts two real things side by side and asks you to make one the right size next to the other. There are no numbers to type and no trivia to memorise. You judge by eye, the game shows you the measurements that actually exist, and you find out how far off you were.
Free, in your browser, nothing to download and no account. The game starts on the first screen.
Unlimited. The well known versions of this format give you one puzzle a day; here you can keep playing as long as you want, which is the only way to actually train your sense of scale.
By ratio, not by absolute error. Being twice as big as the truth and being half as small are the same mistake, so they cost the same. Within about 5% you get full marks; the score falls to zero when you are off by a factor of two.
Every number is either a measurement from a public source or a value this library states it uses, and both are listed on the object library page. The figure a round was scored against is on screen after you lock.
Because your eye reads ratios far better than absolute values. Double an object's height and its area roughly quadruples and its volume roughly multiplies by eight, but the eye still reads it as "about twice as big". Very large and very small things also get flattened into the same bucket of "enormous", which is why a blue whale and a skyscraper feel like neighbours.
Yes. The whole game is one thumb: drag to resize, tap to lock. Nothing needs a keyboard and nothing needs to be installed.
Guess the Size asks you for one dimension of a single object. Bigger or Smaller is the two-choice version, and the fastest thing to play on a bus.
A size comparison is the only honest way to see how wrong a map can be. Africa is about 30.4 million square kilometres and Greenland about 2.2 million, a factor of roughly fourteen — yet on a Mercator map they look like relatives. Once you have judged a pair yourself, that distortion stops being a fact you memorised and becomes something you can see.
Area is the dimension humans under-read most reliably. Length is the one we can argue about. That is why the game shows both measurements after every round: the gap between them is where the mistake lives.
And then there are the tricks your vision plays on purpose. The Moon illusion makes the Moon near the horizon look larger than it is overhead. The Ebbinghaus illusion shrinks a circle surrounded by big ones. The Ponzo illusion uses converging lines to stretch whatever sits further away. The Ames room tilts a floor so two people of the same height look like a giant and a child. Some tour operators still exploit it by holding a tourist up against Stonehenge and taking a photo.
Within about 5% the round scores 100. Off by a factor of two, it scores 0. Twice as big and half as small are the same miss, so they cost the same. That is a different game from a daily puzzle that ends after one pair.