Slope & Angle Meter (Phone Level) | Converting Sun Slope, %, 1/n and Floor Tilt 6/1000, with Chart
The Slope & Angle Meter (Phone Level) uses your phone's tilt sensor to show the tilt of floors, desks, hills, roofs and shelves as an angle (°) and a gradient (%, sun slope, 1/n, and mm per 1 m). No app installation is needed. It supports a bubble-vial mode where you hold the long edge against the surface and a round-bubble (2-axis) mode where you lay the phone screen up, and the flip method, which measures twice in the same spot with the phone reversed, corrects offsets from the sensor or the case. You can hold a measured value, or set the current surface as the 0° reference to measure angle differences. Even on a computer without a sensor you can convert things like how many degrees a 4-sun slope is, what percent 1/12 is, and how many degrees 6/1000 is; calculate roof and hip stretch ratios; work out height, run and slope length from a slope and one length; find the ramp length and number of landings from a step height; look up charts of sun slope, %, 1/n and angle; and compare against standards for floor tilt (3/1000, 6/1000), ramps (1/12, 1/15) and drain pipes (1/50, 1/100).
Hold your phone against a surface to measure its tilt
Uses your phone's tilt sensor to show the slope of floors, desks, hills, roofs and shelves as an angle and a gradient (%, sun, 1/n, mm per 1 m). No app installation is needed.
Align the long edge of your phone with the direction of the slope you want to measure (the uphill direction). It measures the same whether you lay it screen up or stand it on its long edge.
Offset correction (flip-method calibration)
Because of sensor quirks or differences in phone case thickness, a level surface may not read 0°. Measuring twice in the same spot with the phone facing the opposite direction lets you find both that offset and the true tilt of the surface at the same time.
- Place the phone on a flat spot such as a desk or floor and press "Record 1st reading" (wait about a second without touching it)
- In the same spot, rotate the phone 180° horizontally (so the top and bottom are reversed) and set it down again
- Press "Record 2nd reading" and the offset is saved as a correction value
Please press "Measure with tilt sensor" first.
Current correction: long edge 0°, short edge 0° (saved in this browser)
Tips for accurate measurement
- A phone with a camera bump will tilt when laid flat. Stand it on its long edge, or place it on a flat board or ruler for an accurate reading.
- It can only measure over the length of the phone (about 15 cm). For a wide surface such as a floor, place the phone on a long board or timber and average the tilt between two distant points.
- Do not use this for building inspections or construction pass/fail decisions. Verify with a dedicated level, laser or surveying level.
Sensor values, entered content and correction values are used only inside this browser and are never sent to a server.
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About Slope & Angle Meter (Phone Level) | Converting Sun Slope, %, 1/n and Floor Tilt 6/1000, with Chart
The Slope & Angle Meter (Phone Level) uses your phone's tilt sensor to measure the tilt of floors, desks, hills, roofs and shelves, and shows it as an angle (°) and a gradient (%, sun slope, 1/n, and mm per 1 m). A slope is the rise relative to the horizontal distance traveled: a 4-sun slope is 4/10, about 21.8°; a ramp of 1/12 is about 8.3% and about 4.76°; and a floor tilt of 6/1000 is about 0.34°. Even on a computer without a sensor, you can convert between degrees, %, sun, 1/n and per mille, calculate roof stretch ratio (1.0770 for 4 sun) and hip stretch ratio, work out height, run and slope length from a slope and one length, and find the ramp length and number of landings from a step height. When measuring, the flip method, which measures twice in the same spot with the phone reversed, corrects offsets from the sensor and the case.
How to use Slope & Angle Meter (Phone Level) | Converting Sun Slope, %, 1/n and Floor Tilt 6/1000, with Chart
- 1Open this page on your phone and press "Measure with tilt sensor" (on iPhone and iPad, choose "Allow")
- 2Choose whether to hold the long edge against the surface (slopes, roofs, shelves) or lay the phone flat, screen up (floors, desks)
- 3First, do the "Offset correction" on a flat spot. Record the 1st reading, rotate the phone 180° and set it down again, then record the 2nd reading
- 4Hold the phone against the surface you want to measure, and once the value is stable, read the angle, %, sun slope, 1/n and mm per 1 m
- 5To work from numbers on a computer or a drawing, calculate on the "Convert slope" or "Height, length & ramp" tabs
- 6Paste the result into notes or chat with "Copy result", or share it with "Copy URL for these settings"
Great for
- You want to know how many degrees a 4-sun or 5-sun roof is, and what its stretch ratio is
- The floor of your house feels tilted, and you want to check the rough tilt (how many /1000) with your phone
- You are placing a ramp at an entrance step and want to calculate how many cm of length 1/12 or 1/15 requires
- You want to know how many mm to lower a drain pipe, gutter or balcony water slope when making it 1/100 or 1/50
- You want to know how many degrees a 10% road-sign hill or a 17% parking ramp is
- You want to mount shelves, a wooden deck or a laundry pole level in a DIY project, or hang a picture frame straight
- You don't have a level and want to measure tilt right away with the phone in your hand
Good to know
- Phone sensors have an offset of roughly ±0.1 to 0.5° depending on the device. Correcting with the flip method cancels out the offsets of the sensor and the case together.
- It can only measure tilt over the length of the phone (about 15 cm). For a wide surface such as a floor, placing the phone on a long board or timber makes the result less affected by local bumps.
- A phone with a camera bump will tilt when laid flat, so stand it on its long edge or place it on a flat board to measure.
- The floor slopes of 3/1000 (about 0.17°) and 6/1000 (about 0.34°) come from technical standards used as a reference in housing dispute resolution in Japan, and are values measured between two points at least 3 m apart. A phone is not accurate enough to judge the boundary, so use it only as a rough guide.
- Ramps (1/12, 1/15, 1/8), drain pipes (1/50, 1/100) and parking lot driveways (17%) are slopes commonly used as guidelines in laws and design standards. For construction or applications, check the latest laws, ordinances and manufacturers' installation standards.
- Sensor values, entered numbers and correction values are used only inside this device's browser and are never sent to a server.
Questions this tool answers
Use Slope & Angle Meter (Phone Level) | Converting Sun Slope, %, 1/n and Floor Tilt 6/1000, with Chart for searches like these:
- I want to use my phone as a level
- I want to know how many degrees a 4-sun slope is
- I want to convert slope % to angle
- I want to calculate the length needed for a 1/12 ramp
- I want to know how many mm to lower a drain pipe at 1/100
- I want to know how many degrees a floor tilt of 6/1000 is
- I want to see roof stretch ratios in a chart
- I want to measure an angle in the browser without installing an app
FAQ
- How many degrees is a 4-sun slope?
- About 21.8°. A sun slope states how many sun it rises for every 10 sun (1 shaku) traveled horizontally, so a 4-sun slope is rise ÷ run = 4/10 = 0.4, and the angle is arctan(0.4) ≈ 21.80°. A 3-sun slope is about 16.7°, 5 sun is about 26.6°, 6 sun is about 31.0°, and a 10-sun slope (kane-kōbai) is exactly 45°.
- How many percent and degrees is a 1/12 slope?
- A 1/12 slope rises 1 for every 12 traveled, which is about 8.33% and about 4.76°. Under Japan's barrier-free law accessibility standard for buildings, ramps used by wheelchairs must be no steeper than this, and the outdoor guidance standard calls for 1/15 (about 6.7% and about 3.81°). To climb a 45 cm step at 1/12 you need 5.4 m of horizontal length.
- How many degrees is a floor tilt of 6/1000? Can I measure it with a phone?
- 6/1000 is a tilt of 6 mm per 1 m, about 0.34°. 3/1000 is about 0.17°. Under Japan's technical standard for housing dispute resolution, a tilt under 3/1000 is considered unlikely to indicate a structural defect, while 6/1000 or more is considered likely. Because phone sensors are off by roughly ±0.1 to 0.5°, even flip-method correction may not be enough to judge the boundary. Use it for a rough check, and have a professional measure if you are concerned.
- How many mm should I lower a drain pipe for a 1/100 slope?
- A 1/100 slope lowers the pipe 10 mm (1 cm) for every 1 m traveled, so a 5 m drain pipe drops 50 mm. At 1/50 it is 20 mm per 1 m. For horizontal indoor drain pipes, 1/50 for a diameter of 65 mm or less and 1/100 for 75 and 100 mm are commonly used as minimum slope guidelines. Enter the distance on the "Height, length & ramp" tab to calculate the drop.
- What are the roof stretch ratio and the hip stretch ratio?
- The stretch ratio is the slope length per 1 of horizontal length, found as √(1 + slope²). Roof area is the area seen from directly above × the stretch ratio; the stretch ratio is 1.0770 for 4 sun and 1.1180 for 5 sun. The hip stretch ratio is the coefficient for the length of a hip rafter (the diagonal member at a corner of a hip roof), √(2 + slope²), and is 1.4697 for 4 sun.
- Pressing "Measure with tilt sensor" on my iPhone does nothing
- In Safari on iPhone and iPad, you are asked for permission to access "Motion & Orientation" when you press the button, so choose "Allow". If you chose "Don't Allow" once, reopen the tab, or delete this site's data under Settings > Safari > Advanced > Website Data and you will be asked again. Computers often have no tilt sensor; in that case, use the conversion and calculation tabs.
- How do I convert between % slope and angle?
- A % slope is rise ÷ run × 100, and the angle is arctan(rise ÷ run). 10% is about 5.71°, 17% is about 9.65°, and 100% is 45°. Percent and angle are not proportional, so 20% is not double the angle of 10% (11.4°) but about 11.31°.
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