Size It Up is a visual estimation game built around proportional size. Each round places a familiar reference on the left and a resizable target on the right. Your task is to adjust the target until its displayed measurement matches the real relationship between the two objects. A daily game has five rounds, and every round is worth up to 100 points.
The five-step game loop
1. Read the question and measurement axis
Start with the small measurement labels. The round may compare height, length, diameter, or span. This matters. A bridge’s main span is not its total end-to-end length, and a statue’s height may include its pedestal. The question and labels tell you exactly which one-dimensional measurement controls the drawing.
Do not compare area, volume, weight, or mass unless a future mode says so. The visual challenge always uses the named line of measurement. A target at 0.50x is half as tall, long, or wide as the reference along that axis.
2. Build an estimate from anchors
Before moving the target, name a rough relationship in your head. Is it smaller, about the same size, twice as large, or several times larger? Broad brackets are more useful than false precision. If you believe a whale is between two and three bus lengths, begin near 2.5x rather than trying to recall an exact number.
3. Resize the target
On a pointer device, drag the target up or down inside the game canvas. You can also scroll over the target, use the range control, or select the minus and plus buttons. On a keyboard, the arrow keys make small adjustments. The readout reports the visual ratio, but you never need to type a number.
The scale control is logarithmic. That technical detail produces a natural feel: moving between 0.25x and 0.50x takes about the same travel as moving between 1x and 2x. Both changes double the current size.
4. Lock the estimate
Select Lock estimate or press Enter when the proportion looks right. The filled silhouette preserves your choice. A dashed outline reveals the target’s correct proportional size. The result card shows your score, your chosen ratio, the true ratio, and a short scale note.
5. Keep the useful comparison
Read the scale note before moving on. The game is designed to leave you with reusable anchors, not a list of isolated measurements. “The Moon is a little over one quarter of Earth’s diameter” is easier to picture later than a long number in kilometres.
How scoring works
An exact visual match earns 100 points. Scores fall as your proportional error grows. The calculation is symmetric on a logarithmic scale, which means an estimate that is twice the correct size receives the same treatment as one that is half the correct size.
This keeps unlike rounds comparable. Missing a 6.7-centimetre tennis ball by a factor of two is the same kind of visual mistake as missing a planet by a factor of two. Raw metres would make that impossible: the numerical error for a planet would overwhelm every ordinary object.
Your best strategy is not to chase a perfect number. First identify the right order of size, then refine the proportion you can actually see.
Daily challenge and practice mode
The daily challenge selects five rounds from the date in Coordinated Universal Time. Everyone receives the same set, and the next game begins at 00:00 UTC. Progress, scores, streak, and personal best stay in your browser. There is no account and no cross-device sync.
Practice mode is unlimited. Choose Space, Animals, Landmarks, Everyday, or Mixed to receive another comparison after every result. Practice scores do not affect the daily score or streak, so it is a safe place to experiment with the full range of the control.
Controls at a glance
- Drag up or down: resize the target directly.
- Scroll over the target: make fine size adjustments.
- Range control: move across the full scale on touch, mouse, or keyboard.
- Arrow keys: increase or decrease the current estimate in small steps.
- Enter: lock an estimate or continue after a result.
- F: enter or leave the distraction-free fullscreen view. Escape also leaves fullscreen.
Three ways to improve
- Bracket first. Decide “less than half,” “about equal,” or “between two and three times” before touching the scale.
- Use a chain of references. If you do not know a whale directly, compare it with a bus, then compare the bus with the reference on screen.
- Notice the direction of misses. Consistently oversizing animals or undersizing buildings tells you which mental category needs better anchors.
Ready to apply the method? Play today’s Size It Up challenge, or continue with the deeper guide to visual size estimation.