Roof Planner
Lay out panels on a roof before you climb it.
Free to use without an account. A free installer account adds saved work, A4 previews and branded PDF exports.
The roof planner estimates how many panels fit on a roof from its dimensions, panel size, spacing, orientation and obstacle allowance, and reports the array size and occupied area before anyone climbs up.
How the Roof Planner works
Measure the usable roof
Use the clear rectangular area, then subtract a 300 mm walkway margin on each side. The tool applies that margin automatically.
Set panel size and spacing
Enter the panel dimensions in millimetres and the gap between panels. Portrait and landscape orientations give different counts.
Allow for obstacles
Use the obstacle percentage for tanks, vents, chimneys and access paths. Check the coverage warning: above 85% leaves no room for maintenance.
Worked example
10 m × 6 m roof
580 W panels measuring 1,134 × 2,278 mm, 20 mm spacing, portrait orientation and no obstacles.
- 8 panels across × 2 down
- 16 panels maximum
- About 9.28 kWp array
- About 69% roof coverage
Assumptions and limits
- The roof is treated as a clear rectangle with a fixed 300 mm walkway on every side.
- Panel count is a layout estimate, not a structural assessment or a shading study.
- Confirm mounting, wind loading and roof condition with a qualified installer.
Frequently asked questions
How many solar panels fit on my roof?
Enter the usable roof width and length, panel dimensions, spacing and orientation. The planner estimates the grid positions, panel count, array size and occupied area.
Does the planner account for walkways and obstacles?
Yes. Add a walkway margin and an obstacle allowance to reduce the usable area before estimating the panel layout.
Is the roof planner a structural assessment?
No. It is a layout estimate only. A qualified installer should confirm roof condition, mounting and structural capacity on site.
Related tools
Last updated 17 October 2026Maintained by Mishka Energy.
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