There are two different measures of lung breathing capacity: tidal volume, which is the amount of air that flows in and out of your lungs during normal breathing; and vital capacity, which is the maximum amount of air that can move in and out of your lungs. Tidal volume is the breathing you do without thinking. Vital capacity is the equivalent of taking a deep breath before going under water or exhaling deeply after surfacing. In a clinical setting, doctors measure vital capacity with a device called a spirometer. You can take your own measurements with simple household items.

Inflate or stretch the balloon several times to prepare it for the test. A stretched balloon will inflate more easily during the test for a more accurate reading. You are not testing the strength of your exhalation but the volume.

Take the deepest breath you can and blow into the balloon. Release as much air as you can in one breath into the balloon.

Hold the end of the balloon firmly between your fingers as you remove it from your mouth. Do not tie the end or let any air escape.

Have a friend measure the widest part of the balloon with a metric ruler  a ruler with centimeter markings.

Inflate and measure the balloon two more times and write down each number.

Convert each number to a volume measurement by using the lung volume graph at biologycorner.com or at sciencebuddies.org. For example, if one of your measurements is 20 centimeters, the lung volume would be approximately 4,200 cubic centimeters.

Add all three volumes together and divide by three to get the average. For example: 4,200 + 4,500 + 4,100 = 12,800 / 3 = 4,267 cubic centimeters.

Calculate your body surface area, which is proportional to your lung capacity, with the following equation: ([Height in centimeters x Weight in kilograms]/3600) For example: 167.64 centimeters x 68 kg = 11,399.52 / 3600 = 3.16 Find the square root of 3.16 for your body surface area, or BSA, which is 1.77.

Multiply your body surface area by 2,000 to find the vital capacity for women and 2,500 to get the vital capacity for men. For example: 1.77 x 2,000 = 3,540 for women, and 1.77 x 2,500 = 4,425 for men.