How to play

Each duel shows two cards. Size Duel asks one question about one measure: Which is longer?, Which is taller?, Which rises higher above sea level? or Which is heavier? Older Than asks Which came first? Each card says what its value means (for example “diameter”, “ground to tip of the torch”, “opened” or “first published”).

Answering

Tap or click a card, or press 1 or 2 (the left and right arrow keys work too). Your first answer is final. The reveal shows both values, both things drawn to the same scale (or both dates on a time ruler) and a short note. Press Next (or Enter) when you’re ready; nothing moves on by itself.

What makes a duel fair

Duels only compare the same measure. The bigger value must be at least 15% bigger, and for animals and other things that vary, the whole range of typical adults must stay on one side: a bigger-than-usual one could never flip the answer. Dates must be at least two years apart; approximate dates (to the decade or century) need 20 or 200 years. When a source gives a range, the range is used.

Drawn to scale

The silhouettes are original drawings made for Size Duel, each drawn in its real proportions. On the reveal they share one scale: a person (about 1.7 m), a bank card (85.6 mm) or a scale bar shows how big that scale is. When one thing is far too small to see, it is also shown enlarged in a circle, with the enlargement written next to it. Masses are drawn as bars on one scale.

The daily rounds

Each deck has ten duels a day, the same for everyone, from easy to hard. The day changes at midnight UTC. Finish a deck’s round on its own day to add a day to that deck’s streak; your score doesn’t matter. If you start before midnight UTC, you have until 02:00 UTC to finish and still count it. Past days are in the archive; replays never change your streak. Every daily uses new pairings until a deck runs out; a day that includes duels from earlier days is labelled a repeat.

Endless streak and practice

The endless streak goes on until your first miss, gets harder as it grows and never repeats an item before the whole deck has appeared. Practice rounds take ten duels from the whole deck or from one category. Neither changes your daily streak.

Saving

Your round is saved in this browser after every answer. Close the tab and come back: you continue at the same duel. Nothing is sent to a server.