Things You'll Need
Straight board or yard stick
If there is a tree on your property that you believe is in danger of falling, calculate how far it would reach to see if it could damage other property or landscaping. Think back to geometry classes and the iconic right-angled triangle; this basic shape gives you the means of determining the tree's reach by using basic trigonometry (and perhaps a bit of old-fashioned guesstimation thrown in). This method is not accurate down to the inch, but it is still used by forestry experts for tree-felling scenarios.
Hold the yard stick or board and grasp it in one hand so that one it is perpendicular to your cheek (parallel to the ground).
Extend your free arm out at shoulder height. Mark the point on the stick where your fingertips reach to. This distance ranges from 2 to 3 feet for most adults. Break or cut the stick at that mark.
Stand near the trunk of the tree and walk out as many feet as you estimate the tree to be tall. For instance, if you think the tree is 30 feet in height, walk thirty paces from the trunk.
Turn toward the tree. Grasp one end of the stick in your hand like a torch. Hold your arm up and extend it straight out at eye/nose height.
Look up at the tree's top with your eyes only, keeping your head pointed straight ahead. Walk forward or backward a couple of paces at a time until the tip of the tree and the tip of the stick align. Place the stick into the ground, against and perpendicular to the tips of your feet.
Measure the distance to the base of the tree from the stick on the ground, using a tape measure or by counting your paces. If the tree base is 35 feet away from the stick, for instance, the tree's top will land about 35 feet from the base after it falls.