6/12 Roof Pitch: Degrees, Multiplier and What It Means
A 6/12 roof rises 6 inches for every 12 inches of run. That is 26.57°, a pitch multiplier of 1.118 and a slope of 50%. Here is what those numbers do to your roof area, your materials and your quote.
6/12 at a glance
The single most common residential pitch, and the one cost tables are built on.
Nearby pitches
6 in rise per 12 in run
atan(6 ÷ 12) = 26.57°
√(6² + 12²) ÷ 12 = 1.118
6 ÷ 12 × 100 = 50%
Measured something different? The roof pitch calculator takes any rise and run, or an angle, and gives you all four numbers with the full reference chart.
Turn this pitch into a roof size
Measure the roof surface at this pitch, then price the whole job.
What a 6/12 roof pitch means
A 6/12 roof rises 6 inches for every 12 inches of run. It is the most common single pitch on American homes, and it is the pitch that published roofing cost tables quietly assume when they quote a price for a house of a given size. That makes 6/12 the number every other pitch gets compared against.
6/12 in degrees
The angle is the arctangent of rise over run:
atan(6 ÷ 12) = atan(0.5000) = 26.57°
That is the angle between the roof surface and horizontal. It is the number a smartphone level app gives you if you hold it flat against the slope, and the number to enter if a supplier asks for degrees rather than a ratio.
The 6/12 pitch multiplier
The pitch multiplier turns the flat footprint of a roof into its real sloped area. It is the hypotenuse of the rise-and-run triangle divided by the run:
√(6² + 12²) ÷ 12 = √180 ÷ 12 = 1.118
So a 2,000 square foot footprint on a 6/12 roof is about 2,235 square feet of actual roof surface, or 22.4 roofing squares before any waste allowance. Use the roof area calculator to do this for a footprint that is not a simple rectangle, and the roofing square calculator to add a waste factor and convert to squares and bundles.
Why cost tables are built on 6:12
The HomeGuide roof replacement cost guide states in the footnote to its cost-by-house-size table that its figures are based on a single-storey home with a 6:12 roof pitch. You can see the multiplier working inside that table: it lists a 1,000 square foot house as having a 1,120 square foot roof, and 2,000 square feet as 2,235. Divide either pair and you get 1.118, which is the 6:12 pitch multiplier. If your roof is a 6/12, those published figures describe your house directly.
| Footprint | Roof at 6:12 | Roof at 6:12 | Difference |
|---|---|---|---|
| 1,200 | 1,340 sq ft | 1,340 sq ft | +0.0% |
| 1,600 | 1,790 sq ft | 1,790 sq ft | +0.0% |
| 2,000 | 2,235 sq ft | 2,235 sq ft | +0.0% |
| 2,400 | 2,685 sq ft | 2,685 sq ft | +0.0% |
Areas are rounded to the nearest 5 square feet. These are surface-area differences only. We do not publish a percentage for the labour surcharge on steep roofs, because none of the sources this site cites puts a number on it.
Walking on a 6/12 roof
6/12 is the top of the comfortable range. The HomeGuide cost guide puts the threshold for extra safety precautions and extra labour at slopes over 6:12, so a 6/12 roof is the steepest pitch that still prices as ordinary.
Everything is rated for 6/12
6/12 is well above the IRC’s 4:12 underlayment line, so single-layer underlayment applies and no mainstream roofing product is ruled out by slope. It is also steep enough that water and snow clear quickly, which is part of why it became the default.
For what the finished roof costs once you know your square count, see the roof replacement cost guide, or price a specific material with the roof replacement cost calculator.
Sources
- 2024 International Residential Code, Chapter 9 — minimum slopes for asphalt shingles and the underlayment requirement below 4:12 (R905.2.2).
- HomeGuide roof replacement cost guide — the cost-by-house-size table and its 6:12 footnote, and the note that slopes over 6:12 need extra safety precautions and more labour.
- Angle, multiplier and slope percentage are computed from the pitch, not taken from a source. The arithmetic is shown above so you can check it.
Every source on this site is listed on the methodology page. Nobody involved in this site installs roofs.
Related calculators and guides
6/12 roof pitch FAQ
Why do roofing cost tables assume a 6:12 pitch?
Because it is the most common residential pitch. The HomeGuide roof replacement cost guide states in the footnote to its cost-by-house-size table that the figures are based on a single-storey home with a 6:12 roof pitch. If your roof is steeper, the same house has more roof than that table assumes.
What is a 6/12 pitch in degrees?
26.57 degrees. The arithmetic is atan(6 divided by 12), which is atan(0.5).
Can you walk on a 6/12 roof?
Usually yes, and it is the steepest common pitch where that is true. HomeGuide puts the point at which roofs need extra safety precautions and extra labour at slopes over 6:12, so 6/12 sits right at the top of the ordinary range.
Is a 6/12 roof steep?
It is the boundary. Below 6/12 nothing about the slope changes how a roof is priced. Above it, the cost guides start adding for safety equipment and slower work.