Is there a roof pitch calculator app that solves from any two values?
Published · Updated · By Sai Nath
Yes, on Android. The Pitch calculator in MeisterCalc takes any two of Rise, Run, Pitch (X/12), Angle and % Grade and solves the other three, plus slope ratio and sloped length. It is metric first and works offline. Pitch is a paid calculator, and there is no iPhone version yet.
What does the roof pitch calculator do with rise 1500 and run 4000?
Open Home ▸ Pitch, enter Rise 1500 and Run 4000 (millimetres by default) and the results fill in as you type: Angle 20.56°, % Grade 37.50%, Pitch 4-1/2" (the X/12 figure, shown to the nearest sixteenth), Slope Ratio 0.3750 and Hypotenuse 4272.0 mm. A triangle diagram redraws with every change.
The sum behind it is angle = arctan(rise ÷ run) = arctan(0.375) = 20.56°. The how-to guide how to calculate roof pitch works through it by hand, and roof pitch to degrees has the conversion table.
What can I enter, and can it solve from any two values?
Yes. There are five values (Rise, Run, Pitch, Angle, % Grade), so there are ten pairs, and each pair has its own mode: Rise + Run, Rise + Angle, Rise + Grade, Rise + Pitch, Run + Angle, Run + Grade, Run + Pitch, Angle + Grade, Angle + Pitch and Grade + Pitch.
Say you only know the angle. Enter Angle 30 and Run 1000. The Rise comes out at 577.4 mm, the % Grade at 57.74% and the Pitch at 6-15/16" (6.93 in 12). The Angle must be above 0° and below 90°, and the other values must be above zero.
If you enter two ratio values, such as Angle and % Grade, there is no length to work from. The app uses a 1000 mm run so the diagram still draws, and the Hypotenuse only means something when you have entered a Rise or a Run. There is no 1:X field. For a slope of 1 in 3, enter % Grade 33.33 (100 ÷ 3), or read the Slope Ratio (rise ÷ run, so 1 ÷ 3 = 0.3333).
Does it work in metric, and does it suit Australia?
It is metric first: lengths are in millimetres and the angle in degrees, with X/12 alongside. For feet and inches, go to Settings ▸ Units ▸ Default units ▸ Imperial (ft/in); lengths then show in feet, inches and sixteenths. MeisterCalc is made for Australia, New Zealand and the UK, and the interface is English only. The maths is the same everywhere. Pitch rules are not: they come from the NCC in Australia, the NZ Building Code in New Zealand and the Approved Documents in the UK, plus your local council and the roofing manufacturer. The app gives no minimum pitch for any material.
Is the roof pitch calculator free, and does it work offline?
Pitch is not free. Concrete, Stairs and Check Square are the free calculators. The other 12, including Pitch, unlock with a weekly subscription that starts with a 3-day free trial, or a one-time lifetime unlock. Google Play shows the price in your currency. Every calculation runs on the phone with no signal. The network is used only for purchases, analytics and crash reports.
Does it give rafter lengths, roof area or a pitch from the phone's sensor?
No to all three. It does not measure the roof: a tilt-gauge app reads an existing roof with the phone's sensor, while a calculator converts figures you already have. To get those figures, see measuring rise and run with a level and tape. The Hypotenuse is the sloped length of the triangle, not a rafter cut length. There are no hip, valley or birdsmouth cuts, no roof area and no materials list. Roofing calculators are planned for a later version, with no date.
How is that different from other pitch apps?
Some pitch apps only take a rise and a run. The App Store listing for Roof Pitch Calculator (an iPhone and iPad app, checked on 28 October 2026) lists rise and run as its inputs, with pitch as degrees, radians, gradians, per cent and x:12 as outputs. MeisterCalc's Pitch takes any two of five values, and it draws the triangle as you type, so you see the run, the rise and the angle change together.
Other Android construction apps cover more of the roof. Their Google Play listings (checked on 28 October 2026) describe rafter keys with hip, valley and jack rafters and rafter cutting angles, plumb and seat cuts for gable and skillion roofs, feet-inch-fraction entry, and a separate slope and fall calculator. Where they are stronger, that matters if you cut rafters. MeisterCalc does none of the rafter cuts, hips or valleys, and has no feet-inch-fraction keypad.
So the choice comes down to the job. If you need rafter, hip or valley cuts, pick an app that lists them. If you need the angle, pitch, grade and sloped length of a slope from any two numbers, with a diagram that redraws as you type, that is the job Pitch does. Features and prices change, so read each current listing before you choose. For a comparison of Android construction calculators, see best construction calculator apps for Android.
Is there an iPhone version?
Not yet. MeisterCalc is Android only (Android 7.0 or later). You can join the iOS waitlist.