top of page

How to measure a roof

Measuring a roof can be fairly easy depending on the complexity of the roof system. Roofers calculate building materials and pricing based on square footage. A 10'x10' area is 100 square feet or "1 square". One square of roofing equals 3 bundles of shingles.  For simple roof systems measure the length by height. When measuring a more complicated roof system remember to measure triangles, rectangles, and squares.  For triangles multiply the length by height then divide by 2. For squares and rectangles multiply length by height. If your roof area in question is 20'x15' you have 300 square feet or 3 square.

ranch1.png

This roof is 40'x18' per side.  This equates to 720 Square feet or 7.2 square per side.  1,440 square feet in total. Approximately 42 bundles of shingles. Don't forget to consider ridge caps.  1 bundle of 3-tab shingles can cover approximately 35' of ridge. Pre-manufactured ridge caps are available however they're more expensive.

If your not so good with heights there's a few ways you can obtain measurements from the ground. Look at the edges of your roof and find breaks in drip edge.  Drip edge is the metal edge of your roof.  Each piece of drip edge is 10 feet.  You can count how many pieces of drip edge you have along each side of your roof.  If there's smaller pieces make an estimated guess based on the assumption each full piece is 10 feet.  If your roof doesn't have any drip edge you can count tabs or courses of shingles.  Each shingle is approximately 5 inches.  Count how many courses of shingles you have and multiply by 5 inches, then divide by 12 to find how many feet your roof is high.

This hip roof can be measured in three segments then added. L1(15')xH(18') is approximately 135 sqft. or 1.35 square.  Remember to divide triangles in half to find the area of the triangle. L2(25')xH(18') = 450 sqft.  Add 2 triangles ( 135sqft x 2 = 270) and 450sqft to find the area of this side. Approximately 720 sqft or 7.2 square.

hiproof.png

When figuring the total area of your roof don't forget to include the length of your ridges for ridge caps and length of your roof for starter shingles.  Starter shingles are the very first course of shingles underneath your first course of shingles. 1 bundle of 3-tab shingles can cover about 35' of ridge.  One bundle of shingles can cover approximately 85' of starter shingles.  All roof systems require drip edge, shingles, and ridge caps.

written by Robert on 4/23/21

published by RMestimates

bottom of page