Tired of Guesstimating?  Try a Roofing Calculator

Getting Your Roof's Correct Measurement

Without a reliable roofing calculator to help you estimate the size of the roof, you might find it difficult to find out about the cost of your roofing project.  Knowing what kind of cost you'll be looking at will help you plan a budget effectively.

Roofing costs can be unpredictable if you don’t know what's involved and what factors to consider.  If you're planning on re-roofing your home and are feeling a little overwhelmed, don’t be.  There are plenty of tools and resources you can use to help you with your task.  Of course, there are automatic roofing calculators you can use, but if you don’t know how to make the right measurements in the first place, you won't be able to provide the right figures to make the proper calculations.  Here's how to measure your roof correctly:

First things first, a flat roof is easier to measure than a sloped roof.  You just simply calculate for the square footage.  For a sloped roof you'll need to calculate for the pitch.  And yes, you do have to make calculations because even an automated roofing calculator will not be able to determine certain figures.

The Roof Pitch

Next, determine roof pitch or slope.  The pitch is sometimes referred to as the run and rise.  Measure the run by calculating the distance from the center of the building to the outside area of the perimeter wall.  The rise is the distance between the roof's peak and the top portion of the stud wall. 

The pitch refers to the degree to which the roof slopes per foot.  So if you get a 4 in 12 pitch, this means that the roof slopes by 4 inches for every 12 length it runs.  As a comparison, a 45 degree roof has a pitch of 12 in 12.

Sidebar: This section on general topics related to roofing also features articles on mobile home roofing, cost of roofing, roofing franchise and roofing boots.

Next, get a copy of your roof plan.  Check the scale of the plan.  This is your basis for measurement later.  Without a foundation plan, it's difficult to determine the right figures.  Usually, scales come as ¼" to a foot or 1/8" to a foot.  Using the copy of your home's plan and a pencil, square off the sections of the roof.  Count how many squares you've made and measure each, multiplying height times length or width times length.

If you're using the inside dimensions of the house as your basis, don’t forget to add allowance for the roof overhang.  Choose one point and measure carefully.  Measure twice to get a reliable estimate and don't pad your numbers. 

Online Roofing Calculators

No need to tear your hair out if arithmetic is too complicated for you.  There are plenty of resources online you can use that will automatically compute your roofing measurements.  Here are some of them:

RenovationExperts.com

This site has a free online roofing calculator.  Simply click on the drop down menu to pick the area of your home's ground floor.  The measurement unit is per square feet, ranging from 500 to 10,000.  Next, click on your home's roof type and pitch. 

WebCalc.net

This site has a roofing calculator that will show you the amount of materials you'll need.  If you're not too confident about your own calculations, this calculator allows you to indicate your error factor.  After providing that figure and your roof's area, the calculator will come up with the number of materials you'll need, including the underlayment and pounds of nails.

RoofingChildsPlay.com

This site's free roofing calculator will compute roofing requirements for a simple gable roof, a gambrel roof and a hipped roof.  It will also compute roof pitch to degrees, easier if your roof is not a simple, basic construction.  You'll need to provide the front span, front triangle height, rafter length, ridge and hip length and gutter length.

RoofCalculator.com

This is the site where you can purchase the Roof Calculator 6.1.  This software is designed to calculate your roof with just a few figure entries.  Simply provide your roof's rise, span and length and the program will give you an idea of how much roofing material you'll need.  It will also store information such as name, date, time and corresponding calculations.  This program is not free so it's for serious users only.  If you foresee a lot of roofing calculations in your future (in case you're putting up a roofing business someday), this tool will come in handy.