An atlas built
for perspective.

A number is easier to understand when you can put it beside something familiar. Just How Big? brings together illustrated entries, measurements and interactive comparisons to help you build that sense of scale.

Find out what something is, see its size and follow the connections from everyday objects to microscopic life and distant worlds.

Find your starting point

Search for a thing or a quantity, browse a category, or choose two things to compare. Try the games to test an estimate before seeing the real measurements. Teachers can use the free activities and printable resources to explore ratios, units and powers of ten.

What the numbers mean

The atlas connects 733 measured things, 761 quantities and 240 selected comparisons. Each measurement identifies what it describes, its units and its source or modelling assumptions.

Some values are exact definitions or specifications. Others are estimates, representative examples or theoretical scales. Where a recorded range is available, we keep it visible. A chosen example does not stand for every member of its kind.

Measurements and illustrations

Illustrations make a comparison readable; they do not supply the measurements. The marked span in each picture is checked against the recorded value. Some illustrations are AI-assisted and receive editorial review. Rulers and geometric diagrams are used for exact or abstract quantities.

The measurement method explains how we choose values, scale illustrations and describe uncertainty. Comparisons are selected for their usefulness, rather than producing a page for every possible pairing. Descriptions follow the records and their approved sources; we do not invent facts to fill a page.

Help keep it accurate

Just How Big? is published by Katipo Technologies Ltd. If a number, source, illustration or interaction looks wrong, use the corrections and contact page to tell us what you found.