One object, one dimension, no reference beside it. Dial in the measurement you think is real.
How tall is a male giraffe?
Current guess 10 m
Rounds 0Average score —Best —
Guess the size asks you to estimate one dimension of a real object — the height of a giraffe, the length of an aircraft, the width of a doorway — and scores how close you got, not whether you happened to know it. There is no second object on screen, so nothing is given to you for free.
By ratio, on a logarithmic scale. Within about 5% of the measured figure you get full marks, and the score falls to zero once you are off by a factor of two. Twice as big as the truth and half as small are the same size mistake, so they cost the same.
Yes. Free in your browser, no account to create, no daily cap and one slider per round. The daily-puzzle versions of this format give you a limited number of rounds; here you keep going.
Animals, buildings, vehicles, landmarks, mountains and everyday objects. Every object carries exactly one measured dimension — body length, height, or span — and the dimension being asked for is named on screen before you commit.
Yes. A metric and imperial switch sits under the slider and is remembered on your device. Scores are calculated on the true measurement, so switching units between rounds does not change them.
The library spans that range on purpose: a grain of rice at 7 mm, a monarch butterfly at 102 mm, a doorway at 2.03 m, a refrigerator at 1.8 m, a utility pole at 10 m, the Great Pyramid at 138.5 m, the Eiffel Tower at 330 m, Mount Everest at 8,848.86 m. A guess the size game that only asked about buildings would never test the mistake most people actually make, which is that the eye reads small numbers accurately and large numbers very badly.
When two objects are drawn together, you are judging a ratio, and humans are passable at ratios. Asked for a single number with nothing beside it, you have no anchor at all — the figure that comes to mind is assembled from how often you have seen that thing photographed next to a person, a car or a doorway. That is why the aircraft and the whale produce the largest errors on screen: you have almost never seen either one next to something familiar, and the camera has been lying about their scale your whole life.
Within about 5% the round scores 100, and a factor of two scores 0. The daily versions of this format stop after a few rounds. Here the next object starts as soon as you lock.
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 is on screen after every round, and the dimension it measures is named before you commit.