Last updated 10 September 2026
Quick answer: Take a photo of your house side on, open the free Roof Tilt Calculator, drag the blue line along the roof edge and the green line along something level like a brick course. The angle between them is your roof pitch. The photo never leaves your phone.
Roof pitch is the second number every solar calculation wants, after direction. Builders quote it as a ratio like 5:12, installers talk in degrees, and most homeowners have no idea what theirs is. You can measure it in a couple of minutes with your phone camera and a bit of dragging. Here’s how.
What is the Roof Tilt Calculator for?
It measures the angle of a roof surface from horizontal, using a photo. A flat roof is 0°. Most Australian hip and gable roofs sit between 15° and 25°, and 22.5° is the most common pitch on project homes built since the 1990s. The tool gives you the angle in degrees, the rise to run ratio, and the nearest standard pitch, so you can speak both languages.
If you want the background on why pitch matters (and why it matters less than people think), we covered that in how steep is your roof, and does it matter for solar. This post is the practical bit.
How do I take the photo?
Stand at the end of the house where you can see the triangle of the gable, as square on as you can manage. Hold the phone level and step back until the whole roof line fits in the frame. On a phone you can take a photo on the spot or pick one from your library. On a desktop you can drag and drop a file.
The further off square you are, the more perspective skews the angle, so it’s worth the extra 30 seconds to line yourself up. Avoid the very edges of a wide angle lens too, because they bend straight lines.
How do I use it?
Step one: load the photo. Two lines appear over it, a blue one and a green one, each with a handle at both ends.
Step two: drag the blue line’s handles so it runs along the sloping roof edge. The fascia board or the edge of the tiles is the easiest thing to follow. Make the line as long as you can; a longer line averages out small placement errors.
Step three: drag the green line along something you know is level in real life. A brick course, the gutter, a slab edge or a fence rail all work. Again, longer is better.
The tilt reads out live as you drag. On a phone a magnifier pops up under your finger so you can see exactly where the handle sits, and you can pinch to zoom the photo for the fiddly bits.
How accurate is it?
With a decent square on photo you’ll land within 2 to 3° of the true pitch. For solar that’s plenty. Across the range of normal roof pitches the annual yield difference is only a few per cent, so a 22° roof and a 25° roof produce close to the same amount over a year.
If you can’t get a square on photo at all, the common pitches listed under the tool are a fair fallback: 22.5° for most project homes, 2° to 10° for skillion roofs, 30° or steeper for older terracotta roofs.
Is my photo uploaded?
No. The photo is processed entirely in your browser and never leaves your device. That’s also why a shared link carries the measured angle but not the photo itself. If you want someone else to see the picture, send it to them the normal way.
What do I do with the number?
Pair it with your azimuth. The link under the result sends the tilt straight into the Solar Panel Angle Calculator, and if you measured direction first with the Roof Azimuth Calculator you’ll have both numbers ready to go. The angle calculator then tells you what share of the ideal solar yield your roof captures. The tilt is also handy for the Roof Area & Panel Calculator, which uses it to convert the flat area you draw on the map into the actual sloped roof surface.
Already have solar?
Your roof’s tilt never changes. Panel faults, on the other hand, appear without warning and can sit there for months, quietly costing you money while the inverter app shows a green tick. PV Fleet connects to the monitoring your inverter already has, learns what your system should produce and alerts you within hours when it doesn’t. Residential is free to start ($95 a year adds fault alerts), and commercial starts at $790 per site per year. Book a free demo or see pricing.
All six free tools (roof azimuth, roof tilt, panel angle, roof area and panel count, a latitude and longitude finder, and a solar orientation comparison) are on the free solar tools page. No signup, and they work for any address.