Physics 101 

DIY : Make and Use a Barometer to Measure Air Pressure

Overview Air pressure is the result of the weight of tiny particles of air (air molecules) pushing down on an area. While invisible to the naked eye (i.e. microscopic), they nevertheless take up space and have weight. For example, take a deep breath while holding your hand on your ribs and observe what happens. Did you feel your chest expand? Why did it expand?

Air pressure expands because the air molecules take up space in your lungs, causing your chest to expand. Furthermore, air can be compressed to fit in a smaller volume since there’s a lot of empty space between the air molecules.  When compressed, air is placed under high pressure. Meteorologists measure these changes in the air to forecast weather, and the tool they use is a barometer. The common units of measurement that barometers use are millibars (mb) or inches of mercury.

DIY Make a Barometer

A. Materials


B. Theory

How does this measure air pressure?

C. Procedure

0. Place the completed barometer and scale in a shaded location free from temperature changes (i.e. not near a window as sunlight will adversely affect the barometer’s results).

0. In your notebook or the table below, record the current date, time, the weather conditions, and air pressure (i.e. the level where the end of the straw measures on the scale).

0. Continue checking the barometer twice a day (if possible) each day over a four days period.


Data Table

Date Time Weather Conditions Air Pressure
Sample Data Table

Date Time Weather Conditions Air Pressure
June 4, 2003 9:30 am Clear and Sunny 4
June  4, 2003 2:30 pm Cloudy 3
June 5, 2003 9:30 am Rainy 1

Barometer Analysis

Answer the following questions in complete sentences.

1. What problem were you trying to solve with your barometer?

2. Were there any changes in the weather during the week?

3. Did the barometer measurement change when the weather changed? How much?

4. Did the barometer measurement change without a change in weather? Why do you think that happened?

5. How well did your barometer work?

6. What would you change if you could design the barometer again?

7. How do the barometer measurements help us understand the system of weather around us?

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