Introducing SizeItUp: a daily game for your sense of scale

SizeItUp is a free browser game built around one question: how good is your sense of scale? Every day brings five rounds per game, each about a minute long, and every answer comes with a real number and its source.

What you do

Each round puts two shapes side by side. The teal one is a familiar object drawn at its true size, such as a credit card, a tennis ball or the Moon. It never changes, so it works as your ruler. The orange silhouette is the object you have to size. You stretch it until the pair looks true to life, then confirm. The real outline drops on top of your guess, with the measured size and a link to its source.

It sounds easy until you try it. Is a giraffe taller than a woolly mammoth? How many Earths would fit across Jupiter? Most players find their eye is sharp for some objects and way off for others, and that is half the fun.

Five daily games

SizeItUp has five games, each with its own numbered puzzle and its own daily leaderboard:

• Classic: 39 everyday objects, from a dime to the Burj Khalifa, including coins, balls, paper sizes, sports fields and famous landmarks.
• Cosmic Scale: 39 things in space and on other worlds, from moons and asteroids to canyons, stars and spacecraft.
• Prehistoric Giants: 31 dinosaurs and extinct animals set beside animals alive today.
• Kitchen Table: 31 foods and kitchen things, from a peppercorn to a kitchen island.
• Tiny Worlds: 32 small things, from a 1-yen coin down to a single E. coli bacterium.

A new puzzle for every game arrives at midnight in your own timezone.

Every size is sourced

A guessing game is only as good as its answers, so SizeItUp shows its work. Each object names exactly what is measured, such as a planet's equatorial diameter or an elephant's shoulder height. Classic sizes come from published standards, sports rulebooks and official landmark figures. Cosmic Scale draws on NASA and JPL, and the animals on museum specimens, zoos and peer-reviewed papers. Where a source gives a range, the game uses the midpoint and says so.

All 172 objects also have their own page, with metric and US sizes, sources and a to-scale comparison with their nearest neighbors.

Free, fair and in six languages

SizeItUp is free, with no ads and nothing to buy with money. You can play as a guest straight away. Signing in with Google adds a ranked daily leaderboard, streaks that follow you across devices, and Insight, a points balance you spend on cosmetic titles and board themes. Scores are worked out on the server, and the puzzle files your browser loads never contain the answers.

The whole game is available in English, Spanish, Brazilian Portuguese, French, German and Japanese, with numbers and dates written the local way.

Give it a try

Open sizeitup.us, pick a game and see how close you can get. Five rounds, a few minutes, and a much better feel for how big things really are.