You may often hear from a roofing contractor, an architect or a
framing contractor / builder, a phrase “roof pitch”. Roof pitch is the
most common way in US and Canada, to describe the roof’s basic quality –
steepness. Roof can have many other attributes and shapes, but a roof
pitch is often important in pricing a roof, as well as choosing the
correct roofing materials.
Using a roof pitch, you can quickly and accurately calculate the roof
size and amount of roofing materials needed to install a new roof. Most
roofing contractors and estimators use roof pitch as the primary way to
calculate roof area.
What is roof pitch?
Roof pitch or roof slope is a measure of roof steepness or incline,
represented in inches rise of 12 inches run. For example a “3 pitch” or
“3 in 12 pitch” or “3/12 pitch”, all imply that the roof rises 3 inches,
for every 12 inches of it’s horizontal run.
Using a roof pitch, roof footprint, and basic geometry, you can
quickly and with high degree of accuracy calculate the length of the
gable sides, which will then allow you to get very precise roof area
The roof can also be measures in degrees. However, it is often
difficult and unnecessary way to estimate a roof slope, while using roof
pitch is simpler, faster, and often – more accurate. Nevertheless, our
roof pitch calculator provides instant conversion from roof pitch to
degrees and backwards, when you use it to calculate roof pitch.
How to measure and calculate roof pitch:
calculating roof pitch using level and measuring tape:
- Measure 12 inches on the level. Mark the length with
the marker. Many levels are equipped with a ruler on the side, but
marking it will allow it to be more visible.
- Pull out your tape measure about 1 foot or so.
- Use your level to measure the roof run. While holding
the tape measure with one hand, pick up the level with the other and
place its bottom corner on the roof. Using the level's corner as your
pivot point, hold the it parallel with the ground. Pivot it up or down
until the horizontal vial's bubble is between the two lines.
- Measure the rise with the tape measure. Hold the
level parallel to the ground and measure the distance from the roof's
surface to the level's 12-inch mark. Make sure you rotate the tape so it
is perpendicular to the level. Write down the rise.
It is much easier to put the end of the tape on the roof and hold
your hand up. If you decide to measure from the level down, you must add
the length of the tape measure unit itself into the measurement.
- Calculate the roof's slope. The number you measured
with the tape is the roof's rise -- the amount the roof's height rises
over 12 horizontal inches. For example, if you measured 7 inches, the
roof's ratio will be 7:12.
There are two distinctly different methods of calculation the roof
pitch – one is more accurate, while the other is faster and easier.
First method of calculating roof pitch involves climbing up on the roof,
or at least the roof edge and actually measuring the roof pitch using a
carpenter’s level and a tape measure. Second method is more of a
guesstimating way of getting a quick idea of the approximate roof pitch,
while standing on the ground. While not as precise, the second method
allows for a quick calculation, when ladder is not available, or when
you need to get/provide a quick roofing price quote / estimate or
quickly estimate roof size.
Method One – calculating roof pitch using level and measuring tape:
For this most accurate roof pitch calculation, you will need a
ladder, long enough to reach the roof edge, a 2 feet level, and a
measuring tape. Use caution when climbing up the latter, and do not go
onto a roof without adequate fall protection. We also recommend using a
ladder stabilizer to prevent the ladder from sliding to the sides.
Once you reach the top of the ladder, position your level so that on
end touches the roof surface, while the other end is in the air, and it
is leveled. Now measure the distance between the roof surface straight
down from the level’s opposite edge – refer to diagram below:
Method Two – Guesstimating roof pitch off the ground
This process is usually rather easy, fast and pretty accurate, but if you need to order roofing materials for a job, we still recommend getting a more accurate roof roof pitch measurement, such as in the first method.
The basic premise in guesstimating roof pitch, is knowing (measuring)
the width of the roof on the gable side, as well as measuring the
exposure of your siding. Most clapboard siding as well as vinyl siding
has a 4″ exposure, before the next course starts. This means that every 3
runs of clapboard or vinyl siding,
give you exactly one foot rise. You will need to calculate the number
of runs on your siding from the base of the roof (horizontal line where
the roof starts) to the tip of the roof. Most homes will have a 6″ rake
board running along the roof line, so this will add about 7-9 inches to
your roof rise.
Let’s look at an example in the diagram below. The width of the gable
side is 24 feet, plus 3 feet of overhangs (1.5 feet roof overhang on
each side). This gives us a total of 27 feet. The rise is 16 full
courses of 4″ clapboard siding, which equals to 5′ 4″. Add another 8″
for the rake board, and we get a 6 feet rise.
Now we will have to do some math to actually calculate the roof pitch
for both methods described above, but before we do that, I will quickly
talk about measuring the rise if you have something other than a 4″
clapboard or vinyl siding.
If you have a brick exterior on your
house, I would measure the distance of three courses of brick and then
do similar calculations as in the example with clapboard siding. Same
with a cedar shingles – measure exposure of 3 courses for more accurate
total measurements of roof rise. If you have a vertical siding – well,
get a ladder and make actual measurements.