Stand barefoot on the floor. Lift your left leg (if you’re a left-handed person you should lift your right leg).

Close your eyes.

Slowly count up to 30, and check your result with the given table.

You can repeat the action thrice and divide the sum of your time into 3. Most people will have the same result as in the table. The secret is quite simple: our sense of balance gets worse as we get older. However, the numbers can change if you play certain sports that require balance training.