Formulas
- Percent slope = tan(angle) × 100
- mm per meter = tan(angle) × 1000
- Inches per foot = tan(angle) × 12
- Angle = arctan(percent ÷ 100)
At small angles it is nearly linear: 1° ≈ 1.75% ≈ 17.5 mm/m ≈ 0.21 in/ft. Going the other way, 1% is about 0.57°, and 1/4 inch per foot is about 1.19° (2.08%).
Conversion table
| Angle | Percent | mm/m | in/ft |
|---|---|---|---|
| 0.1° | 0.17% | 1.7 mm | 0.02 in |
| 0.3° | 0.52% | 5.2 mm | 0.06 in |
| 0.5° | 0.87% | 8.7 mm | 0.10 in |
| 1° | 1.75% | 17.5 mm | 0.21 in |
| 2° | 3.49% | 34.9 mm | 0.42 in |
| 3° | 5.24% | 52.4 mm | 0.63 in |
| 5° | 8.75% | 87.5 mm | 1.05 in |
Offset by length
The same angle produces a bigger height difference the longer the object.
| Angle | 24 in (61 cm) frame | 48 in (122 cm) shelf |
|---|---|---|
| 0.3° | about 1/8 in (3 mm) | about 1/4 in (6 mm) |
| 0.5° | about 0.2 in (5 mm) | about 0.4 in (11 mm) |
| 1° | about 0.4 in (11 mm) | about 0.8 in (21 mm) |
| 2° | about 0.8 in (21 mm) | about 1.7 in (43 mm) |
Choosing a photo tolerance
The Android app "Level Camera" lets you set the tolerance from ±0.3° to ±5° (default ±1.0°). Tighter is stricter but harder to hit by hand.
| Tolerance | Good for |
|---|---|
| ±0.3° to ±0.5° | Documents shot on a tripod or braced, frames head-on, repeat records |
| ±1° | Handheld listings, products, buildings (default) |
| ±2° to ±3° | Walking-around travel and everyday shots, moving subjects |
| ±5° | When you only want the level as a hint |
Tolerance slider
Set it with the Tolerance slider in Capture settings. It is saved per set, so you can keep, say, Documents at ±0.5° and Travel at ±2°.
Check it on the preview
The current tolerance (±1.0°) is shown at the bottom left of the preview. When the angle falls inside it, the readout turns green and says Level.
FAQ
Can I measure a ramp or drainage slope with my phone?
Only to get a rough idea. Work with a required slope should be checked with a proper level or laser level.
Can the app show millimeters or inches instead of degrees?
It shows degrees only. Use the table above: 1° is about 17.5 mm per meter or 0.21 inch per foot.
Level Camera
No sign-up, and your photos and records stay on your phone. Free on Android.