All you need to measure tree height is a ruler (or yard stick, depending on the height of the tree) and a partner. You'll need to know the height of your partner for calculating tree height.

- Have your partner stand right next to the trunk of the tree.

- You will need to stand away from the tree and face both your partner and the tree. Stand far enough away so that the ruler appears taller than the tree when held at arm's length.

- While holding the ruler in front of you at arm's length, imagine a line running from your eye through the bottom end of the ruler (zero inches) to the feet of your partner (line #1). You will need to maintain this imaginary line during your measurements.

- Moving forward or backward a few feet, adjust your distance from the tree so that another imaginary line (line #2) from your eye to the top of your partner's head goes through the ruler at an easy to read mark (half inch or whole inch mark). This measurement is your partner's height in inches, and should be recorded.

- This measurement and the height of your partner in feet give you the scale from which you will determine tree height. For example, if line #2 goes through the ruler at 2 inches, and the person under the tree is 5 feet tall, the scale would be 2 inches = 5 feet.

- Now imagine a third line (line #3) going from your eye through the ruler to the top of the tree. This is the height of the tree in inches and should be recorded.  Keeping with the prior example, let's say line #3 intersects the ruler at 8 inches.  Since 2 inches equals 5 feet, then 8 inches equals 20 feet. The tree is 20 feet tall.