Guess the Size
Five objects a day, the same for everyone — how close can you get?
What Is the Size Guessing Game?
Guess the Size is a daily estimation game: you see a familiar reference object drawn as a black silhouette at its true scale, and next to it a mystery object as a white silhouette that you resize yourself. Drag the handle, scroll, or tap the slider until your white silhouette looks the right size compared with the reference, then lock in your estimate. The real size is drawn in red over your guess, and you score by how close you got — pure accuracy, no time pressure. Every object's true size is a checked encyclopedia figure, shown with a source link the moment you lock in. It's the estimation counterpart to the number games like the make the number daily: quick, honest, and slightly humbling.
How to Play: Estimate, Guess, Score by Accuracy
- Study the reference. On the left is a black silhouette of an everyday object — a credit card, a door, a school ruler — with its real size printed on the ruler above it.
- Resize the white silhouette on the right until it looks right: drag its corner handle, drag or scroll on the target itself, move the slider, or use the arrow keys (hold Shift for fine steps).
- Lock in with Enter or the Lock in button. The true size is drawn in red over your guess, with the error as a percentage and one interesting fact about the object — plus a source link for the figure.
- Score by accuracy. The closer you get, the more the round is worth:
| Relative error | Points |
|---|---|
| within 6% | 100 |
| within 12% | 90 |
| within 1/5 (20%) | 78 |
| within 1/3 (33%) | 62 |
| within 2× or ½× | 45 |
| within 3× off | 30 |
| 5× off or worse | 0 |
Daily Size Challenge: Five Objects Every Day
Every day at midnight UTC there's a new set of five objects — the same five for everyone, drawn from the full mixed pool of animals, landmarks and everyday things. Rounds are weighted ×1, ×1, ×2, ×3, ×3, so a perfect day scores exactly 1000 points: the harder objects come later and count more. Finish all five to keep your 🔥 streak alive, then compare totals with friends — the daily format works exactly like the other HanoiStack dailies, from Futoshiki to Sudoku. Trust matters: every object's true size comes from an encyclopedia or manufacturer specification, and the link is shown right after you lock in, so you can always check the figure for yourself.
Tips: How to Get Better at Estimating Size
- Anchor on objects you know. A credit card is 85.6 mm wide, an interior door 2 m tall, a US quarter 24.3 mm across. Store a few of these and every mystery object gets a bracket.
- Use your own body as a ruler. Your height, your hand span (~20 cm), your foot, and your stride (~75 cm) travel with you everywhere — compare the silhouette to a remembered person.
- Compare to the reference, not to nothing. The reference is drawn at its true scale; ask “how many credit cards long is it?” rather than guessing in the abstract.
- Halve and double as sanity checks. If the target looks about twice the reference, say so out loud, then check the arithmetic. People are surprisingly good at “bigger or smaller?” and surprisingly bad at absolute numbers.
- Respect the exponent. Our errors are mostly factors of 2 and 10. Before locking in, ask whether you might be off by a whole ×2 or ×10 — fixing one of those is worth far more than a 5% polish.
Size It Up vs Magnitude vs Guess the Size
Estimation games have been around school classrooms for decades — Fermi problems, “How Big Is It?” slide decks, and apps that ask you to drag a slider until a giraffe matches a door. Some popular variants hide the reference entirely and ask for a bare number, which is a memory test as much as an eye test; others present photographed objects whose apparent size depends on the zoom of your screen. Guess the Size keeps it simple and honest: silhouettes drawn at one shared scale, a reference you can trust, five objects a day, and scoring purely by relative error. There's no download, no account, and nothing to configure — open the page and lock in your first guess, free, today and every day.
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