Roof Slope Multiplier

Slope Multiplier – The roof pitch/slope multiplier is responsible for giving an accurate pitch measurement of the roof. This makes measuring easier, knowing that you are able to get the exact measurement of roofs by merely standing on the ground.

This can be done by roofing contractors as well as home owners so they can know how much the roofing contractor will charge them per square foot of the roof.

For roofing contractors who are using this method, it makes it easier for them to estimate the size of the roof, calculate the cost and amount of roofing materials required, as well as provide every home owner an accurate roofing estimate of the area of the roof.

It is not easy to measure the slope of the roof, especially when you have a three-story house.

That is why the roof slope multiplier is needed to provide a nearly exact calculation of the slope. This is one of the methods for measuring roof slope and can be done in different ways.

This gives the roofing contractors and home owners a quick and easy measurement of the roof for specific purposes. It is also more convenient and eliminates worry about the measurement since using this method provides the exact calculations that they need.

The roof pitch multiplier table is very helpful in giving correct and reliable roof measurements and uses Pythagorean Theory.

Accurate roof calculations are achieved using this table and all you need to do is measure the roof width and length, and then you are ready to do a roof pitch measurement. Just multiply the roof width by roof length, and then the result should be multiplied by the use of the pitch multiplier.

Roof pitch multiplier chart

Roof Pitch Roof Pitch Multiplier
2/12 1.01
3/12 1.03
4/12 1.05
5/12 1.08
6/12 1.12
7/12 1.16
8/12 1.20
9/12 1.25
10/12 1.30
11/12 1.35
12/12 1.41
14/12 1.54
16/12 1.67
18/12 1.80
20/12 1.94
22/12 2.09
24/12 2.24


Example calculations:
Roof is 8/12 pitch and measures at 1900 square feet
1900 x 1.2= 2280
2280 – 1900= 380 feet added for pitch

If the home measures 20 X 40 and has a 7:12 roof, then to calculate the slope of the roof follow these steps:
Step 1: Multiply 20 and 40 which equals 800.
Step 2: Find the value of 7:12 from the roof slope multiplier table which is 1.16.
Step 3: Multiply Step 1 and Step 2, i.e. 800 multiplied by 1.16.
Step 4: The value arrived at, 928, reflects the square feet of the roof.

Measuring roof area is an arduous task but through the help of the roof pitch multiplier and roof slope multiplier, it becomes easier and more convenient.

You do not need to hire roofing contractors to do the work for you, which allows you to save time and money. A simple roof is not too difficult to measure, unlike roofs that have a complicated design.

In addition, using these methods for roof measurement give you accurate measurements which helps you achieve a sense of accomplishment and peace of mind as well.

Founder & Editor

Hi, I’m Jim. I was a roofing constructor for 20 years, before deciding to start and gather the best content about roofing. I love woodworking and construction and it was only natural for me to start this passion project of mine. Thank you for visitng.