Make a clinometer
Make a simple clinometer using a straw, protractor, string, and weight to measure tree and building heights by sighting angles and calculating distances.
About this activity
Make a simple clinometer using a straw, protractor, string, and weight to measure tree and building heights by sighting angles and calculating distances.
What you need
Step by step
- 1
Step 1
Gather all the materials on a flat table so everything is ready to build your clinometer.
- 2
Step 2
Tape the straw along the straight edge of the protractor so the straw points outward from the protractor center and lines up with the middle mark.
- 3
Step 3
Push the string through the protractor center hole and tie the washer or nut to the free end so the weight hangs below the protractor.
- 4
Step 4
Trim the string to about 10 to 15 centimeters from the center to the weight so the weight can swing freely past the degree marks.
- 5
Step 5
Hold the clinometer with the flat edge horizontal and note the protractor degree where the string rests to record your zero-angle offset.
- 6
Step 6
Measure a straight ground distance from where you will stand to the base of the tree or building and write down that distance in meters.
- 7
Step 7
Stand at the measured spot, hold the clinometer up to your eye, look through the straw at the top of the object, and read the angle where the string crosses the degree marks.
- 8
Step 8
Subtract the zero-angle offset from the read angle to get the corrected sighting angle and write down that corrected angle.
- 9
Step 9
Measure the height from the ground to your eye level and write down your eye height in meters.
- 10
Step 10
Use a calculator to compute the object's height by calculating height = distance Ă tan(corrected angle in degrees) and then add your eye height to that result.
- 11
Step 11
Share a photo and description of your finished clinometer and the height you measured on DIY.org
Fun facts
How do I build and use a simple straw clinometer to measure a tree or building height?
Tape a straw along the straight edge of a clear protractor so you can sight through it. Thread a string through the protractorâs center hole and tie a small weight (washer) to the end so the string hangs freely. Hold the clinometer at eye level, sight the straw to the top of the object, and read the angle where the string crosses the protractor. Measure the horizontal distance to the base, then calculate height â tan(angle) Ă distance + your eye height. Take several readings and average them.
What materials do I need to make a straw and protractor clinometer?
Youâll need a clear plastic protractor, a straight drinking straw, about 30â50 cm of lightweight string, and a small weight (washer or nut). Also bring tape or glue to fix the straw, scissors, a measuring tape or ruler to measure distance and eye height, and a calculator or smartphone for tan(angle) calculations. Optional items: marker to mark eye level, clipboard, or a clothespin to hold the string while setting up.
What ages is making a clinometer suitable for?
This activity works well for children about 8 years and up with adult guidance; ages 11â14 can handle most steps independently while learning basic trigonometry. Younger children (5â7) can participate by sighting and measuring distances while adults do angle reading and calculations. Itâs a great introduction to measurement, observation, and simple mathâadjust explanations and supervision to match each childâs attention and math skills.
What are the benefits and safety tips for using a homemade clinometer?
Using a clinometer builds spatial reasoning, measurement skills, and an introduction to trigonometry while encouraging outdoor exploration and teamwork. Safety tips: stay on stable, level ground away from roads; donât climb on unsafe surfaces to sight; avoid pointing toward the sun; supervise children when near streets or steep slopes. Variations include using a phone clinometer app, a longer sighting tube for accuracy, or the shadow method for a no-angle alternative.
Watch & Learn
Need help?
What can I use instead of a protractor or washer if I can't find them?
If you don't have a protractor print a protractor template or draw degree marks on stiff cardboard and if you lack a washer or nut tie a small coin or a bent paperclip to the string so the weight still hangs below the protractor while keeping the straw and tape from the instructions.
My string keeps getting stuck or the straw isn't aimed correctlyâhow do I fix the clinometer?
Retape the straw so it points outward from the protractor center and lines up with the middle mark, enlarge the center hole slightly and retie the string so the washer can swing freely past the degree marks, trim the string to about 10â15 cm if it's too long, and then re-check the zero-angle offset while holding the flat edge horizontal.
How should I change the steps or help for younger children or make the activity more challenging for older kids?
For younger children have an adult pre-tape the straw, push and tie the string and measure the ground distance and eye height, and help with the height = distance Ă tan(corrected angle) calculation, while older kids can assemble the protractor themselves, take multiple angle readings from different measured distances, and compute and compare results independently.
How can we improve accuracy or personalize the clinometer beyond the basic instructions?
Personalize your clinometer with colored tape and labeled degree marks, improve accuracy by measuring a longer ground distance and averaging several corrected sighting angles, or mount the protractor on a small tripod to keep the flat edge horizontal while sighting.