Choose a calculation mode, enter measurements, and submit. Use this for patio shade, greenhouse doors, raised beds, or plant seating zones.
- Drop = Mounting height − Front height
- Projection = Drop / tan(Pitch angle)
- Drop = Projection × tan(Pitch angle)
- Pitch angle = arctan(Drop / Projection)
- Fabric length = (Projection + Overhang) / cos(Pitch angle)
- Area ≈ Width × (Projection + Overhang) (plan view)
- Shadow ≈ Front height / tan(Sun altitude) (optional estimate)
- Select a mode based on the unknown you need.
- Choose a unit and keep all inputs consistent.
- Enter mounting height and either front height or projection.
- Add a small overhang for sensitive plants near edges.
- Click Calculate to view results above the form.
- Use the export buttons for records and planning notes.
Sample scenarios for garden patios and planting edges.
| Scenario | Mounting Height (m) | Front Height (m) | Pitch (°) | Projection (m) | Overhang (m) | Total Projection (m) |
|---|---|---|---|---|---|---|
| Patio seating shade | 2.60 | 2.10 | 15 | 1.87 | 0.10 | 1.97 |
| Raised bed protection | 2.40 | 2.00 | 18 | 1.23 | 0.15 | 1.38 |
| Greenhouse doorway cover | 2.30 | 2.05 | 12 | 1.18 | 0.05 | 1.23 |
Projection planning for garden shade zones
Awnings can reduce heat stress on seating, seedlings, and container plants by limiting direct midday sun. This calculator estimates projection using mounting height, front clearance, and pitch angle, so you can target consistent shade without sacrificing headroom or access to beds.
Pitch angle and water management targets
Pitch influences drainage and fabric tension. A steeper pitch moves water away from the wall, lowering splash near planters. The tool highlights low-pitch setups and lets you scale a simple rain guideline using the Rain Factor for dry, moderate, or wet garden climates.
Coverage area and layout decisions
When width is provided, shading area is calculated as Width × Total Projection. Use this to compare coverage across patios, pergola edges, and greenhouse doors. For example, a 3.0 m wide awning with 2.0 m total projection provides about 6.0 m² of plan-view shade.
Overhang for plant edge protection
Plants close to the drip line can still receive strong sun and wind-driven rain. Adding 0.05–0.20 m of extra overhang often improves leaf protection for herbs, blooms, and seed trays placed along the edge. The calculator adds overhang to both total projection and fabric length.
Fabric length, hardware load, and checks
Fabric length is estimated along the slope using (Projection + Overhang) / cos(Pitch). Longer runs generally increase arm forces and mounting demands, especially above 3.5 m projection. Confirm fastener capacity, wall structure, and local wind exposure before installation. Measure twice, then validate clearances on site.
1) Which mode should I use?
Use Projection mode when you know mounting height, front clearance, and pitch. Use Drop mode when you know projection and pitch. Use Angle mode when you know both heights and projection.
2) What is a practical front clearance for patios?
For walkways and seating, many installations aim near 2.0 m or higher at the front edge. Lower clearances can work for plant benches, but verify headroom and door swing.
3) How does overhang change my results?
Overhang adds directly to projection, which increases plan-view shade area and fabric length. It is helpful when plants sit near the edge and need more consistent protection.
4) Why is my projection larger at low pitch angles?
At a lower pitch, the same drop requires more horizontal run. Because Projection = Drop / tan(Pitch), small pitch changes can noticeably increase projection requirements.
5) Can I use feet or inches?
Yes. Select ft or in under Units and enter all measurements in that unit. The calculator converts internally for accurate geometry and shows outputs in your chosen unit.
6) Is the shadow estimate exact?
No. It is a simplified estimate using sun altitude and front height, intended for quick planning. Nearby buildings, plant height, and awning angle details can change real shadow patterns.