Catch the ruler!

Catch the ruler!

Test your reaction time. Are you quicker than your friends?

Who has the quickest reaction time? Find out with this experiment.

What you need:

  • A ruler
  • Pen
  • Paper
  • Friends or family

How to find out who has the quickest reaction time:

  1. Hold the ruler at head level with your arm stretched out. Make sure the ruler is vertical. Holding the ruler with your thumb and index finger at the end with the highest measurement.
  2. Ask one of your friends or family to catch the ruler with their fingers when you drop it.
  3. Get your friend or family member to put their thumb and index finger at the bottom of the ruler, slightly open. They should not be touching the ruler.
  4. Drop the ruler. Write down the measurement on the ruler where your friend's thumb caught it.
  5. Try this with the rest of your friends and record everyone's results.
  6. Now it's your turn! Ask one of your friends to hold the ruler whilst you catch it.

This table lets you convert distance on the ruler to reaction time. For example, if you caught the ruler at the 30.5 centimetre mark, your reaction time is 0.25 seconds.

Distance on the ruler (centimetres) Reaction time (seconds)
5 0.10
10 0.14
15 0.17
20 0.20
25.5 0.23
30.5 0.25
43 0.30
61 0.35
79 0.40


Who had the fastest reactions?

The person who catches the ruler at the lowest measurement.


The faster you react and grab the ruler, the less time the ruler will be falling.

Our eyes see the ruler being dropped. Signals are sent from your eye along the optic nerve from the eye to the brain.

The brain then sends signals to the muscles in the arm and hand to tell them to catch the ruler.

These signals travel very quickly. Your reaction time in this activity depends on your eyesight and the speed that the signals travel to your brain and from your brain to your muscles.


Repeat the experiment and try it out on lots of people. Do people's reaction times improve with practice? Is there a difference in reaction time between people of different ages? Are your reactions slower when you're tired?

Email Planet Science and let us know your fastest reaction time!