Calculator
Formula used
This calculator uses a simplified surface energy balance, designed for quick planning. It estimates sunlight heating, wind cooling, and moisture-driven cooling.
- Absorbed = (1 − albedo) × solar × (1 − shade)
- h = 5.8 + 4.1 × wind (convective transfer, W/m²·K)
- Heat rise ≈ absorbed ÷ (h × 12)
- Evap cooling ≈ moisture × (1 − RH) × 120 × sunFactor
- Surface ≈ air + heat rise − (evap cooling ÷ (h × 10))
Note: This is an estimate for garden decisions, not a lab measurement.
How to use this calculator
- Pick a surface type that matches your bed or walkway.
- Enter air temperature from a shaded thermometer reading.
- Use typical solar values if you lack a sensor.
- Add wind and humidity for better cooling estimates.
- Set shade percentage from trees, cloth, or structures.
- Adjust moisture factor after watering or rainfall.
- Press Submit to view results above the form.
- Download CSV or PDF for logs and comparisons.
Example data table
| Surface | Air (°C) | Solar (W/m²) | Wind (m/s) | RH (%) | Shade (%) | Albedo | Moisture | Expected outcome |
|---|---|---|---|---|---|---|---|---|
| Bare Soil | 32 | 850 | 1.5 | 35 | 5 | 0.17 | 0.25 | Hot surface; water early; add mulch. |
| Grass/Turf | 30 | 750 | 3.0 | 55 | 20 | 0.23 | 0.60 | Lower peak heat; safer for seedlings. |
| Dark Pavers | 33 | 900 | 0.8 | 40 | 0 | 0.15 | 0.08 | Extreme heat risk; provide shade and barriers. |
Use the table as a reference for typical scenarios.