Whether you want to replace your existing gutters or add gutters to a new home, you’ll need to know the right measurements. Fortunately, you can easily measure existing gutters yourself if you need to replace them. To choose the right size gutters for a building that doesn’t already have them, you can quickly calculate the drainage area of the roof and adjust for pitch and rainfall to find the adjusted square footage. You only need a ladder, chalk, tape measure, level, paper, and pen!
Measure the length of each gutter run. Run the tape measure from 1 corner of the gutter as far as you can go toward the opposite corner. Make a mark with chalk and record the measurement. Carefully climb down the ladder and move it to the chalk mark. Measure from the chalk mark to the opposite corner of the gutter, making another chalk mark and moving the ladder again if necessary.
Continue around the perimeter of your home until you have measured and recorded the entire length of the existing gutters.
Gutters and downspouts are typically sold in 10 ft (3.0 m) lengths.
Measure the height of each downspout. If you have downspouts, position and climb the ladder so you can place the measuring tape at the top of 1 downspout. Measure from the top to the ground, then add 4 feet (1.2 m) to each downspout to account for the angled extension at the bottom that directs water away from the home. Record your measurement, then repeat the process for all the other downspouts
Count the number of corners and end caps. Walk around your home and count the number of corner pieces and end caps on the gutters. Record this information and mark whether the end caps are right or left ends.
Each downspout requires 3 elbow pieces, so add those to your notes as well.