Size It Up: the size guessing game

How big is a Space Shuttle next to a football goal? How wide is Jupiter if Earth is the size of a coin? Size It Up puts a familiar object on the board, then asks you to stretch a second one to its true size. Five rounds make a game, the rounds get harder as you go, and you can play unlimited games for free.

Scoring: five rounds, up to 1,000 points

Each round gives an accuracy percentage, then multiplies it by the round’s weight. The first two rounds are easy and worth up to 100 points each. Round three is medium and counts double. The last two are hard and count triple, so a good finish can rescue a slow start.

Accuracy depends on the ratio between your guess and the answer, never the raw difference. Guessing half the real size costs exactly as much as guessing twice the real size. That keeps a coin round and a planet round equally fair: being off by 2 cm on a coin is as bad as being off by thousands of kilometers on a planet, if both are the same fraction wrong.

Unlimited games and the daily challenge

Size It Up on this page is unlimited. Every time you press Play again, you get five objects you have not just seen, in the same easy, medium and hard order. There is no daily cap and no account.

If you like a shared puzzle, the daily challenge gives everyone the same five objects on the same calendar date. It changes at midnight in your own time zone, keeps your streak in this browser, and lets you compare scores with friends without spoiling the answers.

The reference objects

Every round pairs the object you scale with one you already know. These are the references used in the game, with the measurement each one stands for.

There are 80 objects to scale: coins, gadgets and sports gear, hummingbirds and hippos, dinosaurs from Compsognathus to Diplodocus, aeroplanes and spacecraft, skyscrapers, moons and planets. Measurements are checked against primary references, such as the manufacturer, a sport’s rule book, a zoo or natural history museum, the Cornell Lab of Ornithology, the building’s operator, or NASA.

How to get better at guessing sizes

Count references, don’t eyeball

Before you drag, ask how many references would fit along the thing you are scaling. “About five football goals” or “three Earths across” is easier to hold in your head than a raw number, and it maps directly onto the board.

Check which dimension is measured

Most big misses come from measuring the wrong thing. Aircraft are measured nose to tail, not wingtip to wingtip. The Statue of Liberty is measured from the ground to the torch, including the pedestal. Planets use their equatorial diameter, and Saturn’s rings are not included. The line under each question tells you exactly what counts.

Think in ratios

Because scoring uses ratios, a guess that is 20% too big is as good as one that is 20% too small. If you are unsure, aim for the middle of your range on a multiplying scale. Between 10 and 1,000, that middle is 100, not 500.

Keep a few anchors in your pocket

A handful of memorized sizes makes every round easier. A sheet of A4 paper is 29.7 cm tall. A bank card is about 8.6 cm wide. A regulation football goal is 7.32 m between the posts. An Airbus A320 is about 38 m long. Earth is about 12,756 km across. Chain them together: the Statue of Liberty is roughly two and a half A320s tall.

Use the hard rounds wisely

Rounds four and five count three times. Take your time on them. A careful 80% on a hard round is worth 240 points, more than two perfect easy rounds combined.

Learn from the reveal

After each round, compare the dashed outline with the real size. Did you overshoot or undershoot? If the same thing keeps happening, on small objects or on large ones, you have found your bias, and correcting it is the fastest way to improve.

Size It Up in the classroom

Size It Up works well as a five-minute warm-up for lessons on measurement, scale and ratio. Students can play the same daily challenge on their own devices and compare scores at the end, since everyone gets the same five objects on the same date and the shared result shows no answers.

A few prompts that turn a round into a discussion:

• Before dragging, estimate how many references fit along the object, then check after the reveal.
• Why does guessing half the size cost the same as guessing double? What does that say about comparing a coin and a planet?
• Which measurement was asked for: length, height or diameter? How would the answer change if it were a different one?
• Convert the answer into the reference’s units. Is an Airbus A380 closer to two or three A320s long?

There are no ads in the game area, no sign-up, and nothing to install, so it runs on school laptops and tablets in a regular browser.

Surprising sizes from the game

• A US dime is smaller across than a penny, even though it is worth ten times as much.
• The Space Shuttle orbiter was almost exactly as long as an Airbus A320.
• An Airbus A380 is almost twice as long as an A320.
• The Eiffel Tower is about three and a half times as tall as the Statue of Liberty with its pedestal.
• About eleven Earths fit across Jupiter, and about nine across Saturn before you count its rings.
• Four Earth diameters fit almost exactly across Uranus. Neptune is slightly narrower.
• Mars is a little over half as wide as Earth, and more than five Plutos fit across Earth.

Questions about Size It Up

More games like Size It Up

If you enjoy judging scale, try a different kind of hunch.