size it up.

A little perspective

Trust your eye.

Five comparisons. Two objects each time. How close can you get?

  1. Compare

    The object on the left is your measuring stick. Keep resizing — the view automatically zooms out when you need more room. You can also zoom the canvas; both objects scale together without changing your estimate.

  2. Find the right size

    Drag the blue handle, scroll while hovering it, tap − / +, or use the arrow keys. Match the dimension in the question.

  3. Lock it in

    Reveal the real size and earn up to 100 points. Five rounds add up to a maximum of 500.

The first answer in each round counts. A new challenge arrives every day at 00:00 UTC. Object sizes use the specific examples shown in the answer.

Read the full rules and scoring guide
Practice · not ranked
All past challenges

How long is a T. rex compared with a blue whale?

Use the blue whale as your reference.

01 / 05
Blue whale, reference object for length comparison
T. rex, estimated length relative to the blue whale
Blue whaleReference
T. rexYour estimate
Fine tune
All past challenges
View answers and sources

Answers from this past challenge. Today’s challenge remains a surprise.

  1. Round 1

    How long is a T. rex compared with a blue whale?

    Blue whale, used for the length comparison
    ReferenceBlue whale33.5 m long (maximum)
    T. rex, used for the length comparison
    Compared objectT. rex12 m long

    Illustrations shown individually, not to a shared scale.

    Actual size ratio

    ≈ 0.3582×

    T. rex ÷ Blue whale, comparing length.

    A typical adult T. rex was about 12 metres long. Fossil specimens vary in size.

    Measurement source · nhm.ac.uk

  2. Round 2

    How long is a sperm whale compared with a school bus?

    School bus, used for the length comparison
    ReferenceSchool bus12 m long
    Sperm whale, used for the length comparison
    Compared objectSperm whale15.8 m long (adult male)

    Illustrations shown individually, not to a shared scale.

    Actual size ratio

    ≈ 1.317×

    Sperm whale ÷ School bus, comparing length.

    Male sperm whales reach physical maturity at approximately 52 feet (15.8 metres). This round uses that adult male length.

    Measurement source · fisheries.noaa.gov

  3. Round 3

    How long is a soccer pitch compared with an Airbus A380?

    Airbus A380, used for the length comparison
    ReferenceAirbus A38073 m long
    Soccer pitch, used for the length comparison
    Compared objectSoccer pitch105 m long (international, representative)

    Illustrations shown individually, not to a shared scale.

    Actual size ratio

    ≈ 1.438×

    Soccer pitch ÷ Airbus A380, comparing length.

    International matches set the touchline between 100 and 110 metres. This round uses 105 metres, the middle of that range.

    Measurement source · theifab.com

  4. Round 4

    How long is an orca compared with an African elephant?

    African elephant, used for the length comparison
    ReferenceAfrican elephant6.5 m long (representative)
    Orca, used for the length comparison
    Compared objectOrca9.8 m long (maximum)

    Illustrations shown individually, not to a shared scale.

    Actual size ratio

    ≈ 1.508×

    Orca ÷ African elephant, comparing length.

    Killer whales reach up to 32 feet (9.8 metres). This round uses that upper length.

    Measurement source · fisheries.noaa.gov

  5. Round 5

    How long is a soccer ball compared with a vinyl record?

    Vinyl record, used for the length comparison
    ReferenceVinyl record30.48 cm across (nominal)
    Soccer ball, used for the length comparison
    Compared objectSoccer ball22 cm diameter (representative)

    Illustrations shown individually, not to a shared scale.

    Actual size ratio

    ≈ 0.7218×

    Soccer ball ÷ Vinyl record, comparing length.

    The Laws of the Game require a circumference of 68–70 cm. This round uses a 22 cm diameter, a circumference of 69 cm inside that range.

    Measurement source · theifab.com
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