This is important whether you’re installing new roof tiles, planning a loft conversion, or working out how to achieve proper drainage on your roof. However, if you’re someone who hated maths in school, then this may not be your favourite task.

But don't worry—calculating it isn't as daunting as it sounds. Beesley and Fildes will walk you through calculating roof pitch in degrees, so you don’t end up butchering the process.

What is roof pitch?

The roof pitch refers to the angle at which a roof slopes, which impacts how well the roof deals with rain, snow, and debris.

If your home has two or more sides that slope into a peak, then you have what we call a ‘pitched roof’. A steeper pitch helps water run off faster, which reduces the chance of leaks or pooling (this is especially important in the UK, where we experience rainy conditions most of the time).

Believe it or not, certain roof angles are actually enforced in the UK to meet building regulations, which is why getting it right is so important. This will save you loads of hassle with approvals.

Why measure roof pitch in degrees?

You may be thinking, ‘why not measure roof pitch as a ratio or percentage?’, which some people do, but there’s no guesswork involved when presenting it in degrees.

This is why measuring in degrees is a go-to for so many roofers, designers, and DIYers. Simply put, degrees are universal, in contrast to ratios or percentages, which might differ depending on a place or trade customs.

If you’re working with an architect or engineer or using software for designing plans, they’ll almost always want the pitch in degrees. Why? Design programmes like AutoCAD or SketchUp rely on angular measurements to create accurate drawings, which degrees offer.

Some tiles and slates also have a minimum pitch recommendation, and knowing the pitch in degrees can help you match them up with product specifications.

Tools you'll need

Tape measure
Pencil and notepad
Spirit level
Calculator
Ladder
Safety gear (hard-toe boots, harness, gloves)

A step-by-step guide to calculating roof pitch

You don’t need to be an experienced surveyor or mathematician to calculate the pitch of a roof. All you need to do is follow these simple steps:

1. Measure the run (the horizontal bit)

Using a tape measure or spirit level, measure the horizontal distance to the edge of the roof to a point directly beneath the pitch.

You can do this from inside a loft, measuring along the ceiling joist.

2. Measure the rise (the vertical bit)

Next, use a tape measure again to measure from the top of the ceiling joist straight up to the underside of the ridge board (that’s the pointy top of the roof structure).

You can use a spirit level to make sure you achieve a straight vertical line.

3. Do the maths (or use a calculator)

Once you’ve got your measurements, you’ll need to calculate the pitch using this formula:

Pitch (in degrees) = arctangent (rise ÷ run)

So, just divide the rise by the run to get the tangent, then hit the ‘tan?¹’ or ‘arctan’ button on your calculator.

For example, if the rise is 1.5m and the run is 2.5m, you’ll divide 1.5 by 2.5 to get 0.6. This is the tangent.

Then, convert the 0.6 into degrees by using the arctangent function to get 30.96° or roughly 31 degrees.

Are you using your phone?

Open the Calculator app
Turn your phone sideways (to access scientific functions)
Enter 0.6
Tap the “2nd” or “Inv” button, then hit “tan” — it should now read tan?¹
You’ll see the result in degrees

4. Double-check if you’re not sure

If your measurements seem off, measure again and compare the results.

You can also try measuring from outside using a digital angle finder placed on the actual roof slope (if you’re able to do so).

Common roof pitches in the UK

Now that you’ve got your roof pitch in degrees, you may be wondering if you’re roof pitch is normal, too shallow, or too steep.

Here’s a quick look at some of the most common roof pitches you’ll find across the UK to clear away your worry.

35°–40°: Traditional pitched roofs (Victorian terraces, cottages, Edwardian homes)
30°–35°: Modern family homes (terrace houses, modern builds)
20°–30°: Low-pitch roofs (bungalows, extensions)
10°–20°: Almost flat, but not quite (dormers, lean-tos, and garage roofs)
0°–10°: Flat roofs

Once you’ve sorted out your roof pitch, have a look at our roofing materials to get started on your home renovation or construction project.

With everything from roofing tiles to felt systems and battens, we’re your one-stop shop for affordable and long-lasting roofing materials in the UK. Plus, you can expect expert advice from real people who know their stuff.