# Kemiringan atap: sudut, persen dan kenaikan

> Dari kenaikan vertikal dan jarak horizontal, hitung sudut, kemiringan persen, kemiringan atap (x per 12), panjang miring dan faktor kasau.

Versi interaktif: https://www.calcopenly.com/id/geometry/slope-roof-pitch-calculator
Topik: Kalkulator geometri

Every way of stating a slope comes from one ratio, m = rise ÷ run. The angle from horizontal is arctan m, the percent grade is 100m, the roof pitch is 12m (units of rise per 12 of run), and the rafter factor √(1 + m²) turns a horizontal run into the sloped length. Enter a rise and run, or any one of the other forms, and the rest follow.

The default rise of 6 over a run of 12 is a 6/12 roof: 26.57°, a 50% grade and a rafter factor of 1.1180, so 12 cm of run needs 13.4164 cm of rafter. Ramps and roads use the same numbers: the steepest ramp the 2010 ADA Standards allow, 1:12, is an 8.33% grade, or 4.76°.

Percent grade is not an angle: a 100% grade is 45°, and a vertical face has no finite grade or pitch, so angles must lie between −90° and 90°. A negative rise describes a downhill slope.

## Masukan

- **Ukuran yang diketahui** (pilihan: Rise and run, Sudut, Percent grade, Roof pitch)
- **Rise**: Negative for a downhill slope
- **Run (horizontal distance)**
- **Angle from horizontal**: Between −90° and 90°
- **Nilai**: Rise per 100 of run
- **Pitch**: Rise for every 12 of run, as in a 6/12 roof
- **Satuan hasil** (pilihan: Milimeter (mm), Sentimeter (cm), Meter (m), Kilometer (km), Inci (in), Kaki (ft), Yard (yd), Mil (mi))

## Hasil

- Sudut (°) — hasil utama
- Nilai
- Roof pitch (in 12)
- Ratio (rise : run)
- Rise per unit of run
- Rafter length factor
- Slope length

## Rumus

$$
\begin{gathered} m = \frac{\text{rise}}{\text{run}},\quad \theta = \arctan m,\quad \text{grade} = 100m\,\% \\[6pt] \text{pitch} = 12m \text{ in } 12,\quad \text{factor} = \sqrt{1 + m^2} \end{gathered}
$$

## Contoh penyelesaian

### Rise 6, run 12 (a 6/12 roof)

- Ukuran yang diketahui: Rise and run
- Rise: 6 cm
- Run (horizontal distance): 12 cm
- Satuan hasil: Sentimeter (cm)
- **Sudut: 26.565051 °**
- **Nilai: 50%**
- **Roof pitch: 6 in 12**
- **Ratio (rise : run): 1 : 2**
- **Rafter length factor: 1.118034**
- **Slope length: 13.416408 cm**
- Sumber pemeriksaan: Python 3.8 math: degrees(atan(0.5)), sqrt(1.25), sqrt(6**2 + 12**2)

### 45°

- Ukuran yang diketahui: Sudut
- Angle from horizontal: 45 °
- **Nilai: 100%**
- **Roof pitch: 12 in 12**
- **Ratio (rise : run): 1 : 1**
- **Rafter length factor: 1.414214**
- Sumber pemeriksaan: tan 45° = 1; Python 3.8 math.sqrt(2)

### 8 % road grade

- Ukuran yang diketahui: Percent grade
- Nilai: 8%
- **Sudut: 4.573921 °**
- **Roof pitch: 0.96 in 12**
- **Ratio (rise : run): 1 : 12.5**
- Sumber pemeriksaan: Python 3.8 math: degrees(atan(0.08)); 12 × 0.08; 1/0.08

### 4/12 roof pitch

- Ukuran yang diketahui: Roof pitch
- Pitch: 4 in 12
- **Sudut: 18.434949 °**
- **Nilai: 33.333333%**
- **Rafter length factor: 1.054093**
- Sumber pemeriksaan: Python 3.8 math: degrees(atan(4/12)), sqrt(1 + 1/9)

### ADA ramp 1:12

- Ukuran yang diketahui: Rise and run
- Rise: 1 cm
- Run (horizontal distance): 12 cm
- Satuan hasil: Sentimeter (cm)
- **Nilai: 8.333333%**
- **Sudut: 4.763642 °**
- **Ratio (rise : run): 1 : 12**
- Sumber pemeriksaan: ADA §405.2 maximum ramp slope 1:12; Python 3.8 math: degrees(atan(1/12))

### Flat ground (edge case)

- Ukuran yang diketahui: Rise and run
- Rise: 0 cm
- Run (horizontal distance): 5 cm
- Satuan hasil: Sentimeter (cm)
- **Sudut: 0 °**
- **Nilai: 0%**
- **Roof pitch: 0 in 12**
- **Rafter length factor: 1**
- **Slope length: 5 cm**
- Sumber pemeriksaan: Zero rise: tan θ = 0

## Pertanyaan

### How do you convert percent grade to degrees?

Take the arctangent of the grade divided by 100: θ = arctan(grade/100). An 8% road grade is arctan 0.08 = 4.57°, and a 100% grade is 45°, not 90°. The reverse is grade = 100 × tan θ, so a 30° slope is a 57.7% grade.

### What angle is a 6/12 roof pitch?

26.57°. A pitch of x/12 means x units of rise for every 12 of run, so the angle is arctan(x/12): 4/12 is 18.43°, 6/12 is 26.57°, 8/12 is 33.69° and 12/12 is 45°. The rafter factor for 6/12 is √1.25 = 1.118, so 12 ft of horizontal run needs 13.42 ft of rafter before any overhang.

### What is the maximum slope for a wheelchair ramp?

1:12 under the 2010 ADA Standards for Accessible Design (§405.2): one unit of rise for every 12 of run, an 8.33% grade or 4.76°. Each ramp run may rise at most 30 in (§405.6), so a 30 in rise needs a run of at least 30 ft. Other countries set their own limits in their building codes.

### How do you calculate rise over run?

Divide the vertical rise by the horizontal run, both in the same unit: m = rise/run. A roof that rises 6 in over 12 in of run has m = 0.5. Measure the run horizontally, not along the surface: the sloped length here is 13.42 in, and dividing by it gives 0.447, the sine of the angle rather than the slope.

### Seberapa akurat “Kemiringan atap: sudut, persen dan kenaikan”?

Akurasi bergantung pada masukan dan asumsi metode. Aritmetika desimal memakai 50 digit signifikan, tetapi perkiraan, metode numerik dan data sumber bisa kurang presisi; pembulatan yang ditampilkan tidak menghilangkan batasan itu. Contoh penyelesaian yang diperiksa dengan sumber independen: 8. Misalnya, “Rise 6, run 12 (a 6/12 roof)” diperiksa dengan Python 3.8 math: degrees(atan(0.5)), sqrt(1.25), sqrt(6**2 + 12**2).

### Dari mana metode ini berasal?

OpenStax College Algebra 2e, §4.1 — slope as rise over run; US Access Board, ADA Standards §405.2 — ramp slope 1:12 (8.33 %).

## Sumber

- [OpenStax College Algebra 2e, §4.1 — slope as rise over run](https://openstax.org/books/college-algebra-2e/pages/4-1-linear-functions)
- [US Access Board, ADA Standards §405.2 — ramp slope 1:12 (8.33 %)](https://www.access-board.gov/ada/#ada-405)