Calculator
Example data table
| Scenario | Canopy % | Cloth % | Sun h | Shade h | Season | Micro | Effective % |
|---|---|---|---|---|---|---|---|
| Open bed with light cloth | 10 | 30 | 10 | 1 | 1.00 | 1.00 | 63.0 |
| Tree filtered shade, no cloth | 40 | 0 | 9 | 2 | 0.95 | 1.00 | 44.3 |
| Pergola + cloth + afternoon block | 25 | 50 | 10 | 3 | 1.05 | 1.00 | 29.5 |
| Courtyard with reflective wall | 20 | 30 | 8 | 1 | 1.00 | 1.15 | 66.1 |
Formula used
This calculator treats shade sources as multiplicative losses. Each factor reduces available light, and the remaining fractions multiply together.
- Canopy models overhead filtering from trees or structures.
- Cloth uses the rated shade percentage of the fabric.
- Blocked hours represent full shade during the daylight window.
- Season factor adjusts for sun angle and seasonal intensity.
- Microclimate factor accounts for reflections or open sky exposure.
How to use this calculator
- Pick a representative sunny day and note your daylight window.
- Estimate canopy shade and shade cloth rating, if any.
- Count how many hours the bed is fully blocked by shade.
- Choose a season factor and microclimate factor for your spot.
- Enter full-sun DLI or PPFD, then calculate and review the fit.
- Export your history as CSV or a simple PDF report.
Shade reduction planning guide
Garden light is rarely “all or nothing.” A bed can look bright, yet deliver far less usable energy once tree canopies, shade cloth, and time-based obstructions are combined. This calculator converts those conditions into a single effective light percentage and an estimated reduced DLI, helping you compare spots, seasons, and shade solutions with consistent numbers.
1) What the percentage really represents
Effective light percent is the remaining fraction of full sun after multiplying the losses from canopy, cloth, and blocked hours. For example, 30% canopy and 40% cloth do not equal 70% shade; the remaining light becomes 0.70 × 0.60 = 0.42 (42%) before time blocks and factors.
2) Typical shade cloth data points
Common garden fabrics are sold as 30%, 40%, 50%, and 70% shade ratings. Lighter ratings often support fruiting crops when heat is high, while 50–70% is frequently used for leafy greens, seedlings, and heat-stress protection. Use the rating as a baseline and validate with plant response.
3) Canopy and obstruction benchmarks
Light tree cover can behave like 10–25% shade, while dense foliage can exceed 50% depending on leaf density and sun angle. Blocked hours are especially powerful: losing 3 hours out of a 10-hour window removes 30% of that day’s potential exposure before other losses are applied.
4) Translating results into plant decisions
Many “full sun” vegetables perform best above roughly 70% effective light, while many herbs and ornamentals handle 40–70% well. Shade-tolerant plants often thrive below 40%. If reduced DLI trends low, prioritize pruning, relocation, or seasonal timing rather than pushing fertilizers alone.
FAQs
1) Is shade reduction the same as shade percentage?
No. Shade reduction is calculated after combining multiple losses. Two 30% shade sources don’t equal 60% shade; they multiply, leaving 49% light, not 40%.
2) What is DLI and why does it matter?
DLI is Daily Light Integral, measured in mol/m²/day. It summarizes total light received in a day and correlates well with plant growth, flowering, and yield compared with a single “sunny moment.”
3) How do I estimate blocked hours accurately?
On a clear day, check the bed every hour and note when it is fully shaded by buildings, fences, or trees. Add those shaded hours within your chosen sun window for a practical estimate.
4) Should I use PPFD mode or full-sun DLI mode?
Use DLI mode if you already know typical full-sun DLI for your season. Use PPFD mode if you have a light meter reading and want the calculator to convert it into a full-sun DLI baseline.
5) Why do season and microclimate factors exist?
Season factor reflects sun angle and intensity changes across the year. Microclimate factor accounts for local boosts or losses, such as reflective walls, open sky, or persistent haze.
6) My effective light is above 100%. Is that possible?
The tool allows small boosts because reflection and open sky can increase light compared with a reference. If you see high values, reduce microclimate factor or verify your canopy and shade-hour estimates.
7) What’s a quick target for common crops?
Fruiting crops often prefer 70–100% effective light. Leafy greens commonly do well at 40–70%. Many shade ornamentals thrive at 15–40%, especially with steady moisture and cooler temperatures.