Calculator Inputs
Example Data Table
| Use case | Heat release (kW) | Base diameter (cm) | Wind (m/s) | Estimated height (m) |
|---|---|---|---|---|
| Weed torch, calm morning | 20 | 6 | 0.5 | 0.42 |
| Small burn pile edge | 60 | 15 | 1.0 | 0.78 |
| Fire pit testing, light breeze | 90 | 25 | 2.5 | 0.95 |
Formula Used
The calculator offers three options so you can compare estimates.
Heskestad correlation
Lf = -1.02·D + 0.235·Q^(2/5)
where Lf is flame height above the rim (m),
D is flame base diameter (m),
and Q is heat release rate (kW).
Total flame height is Lf_total = Lf + D.
McCaffrey-style scaling
A practical scaling for small outdoor flames uses
Lf_total ≈ 0.20·Q^(2/5).
It is useful when diameter is uncertain.
Garden torch simplified
A garden torch can be approximated by
Lf_total ≈ 0.18·(Q·η)^(2/5) + 0.5·D,
where η is an efficiency factor.
Adjustments
Small corrections are applied for air density, humidity, and wind. They are kept modest and capped to avoid unrealistic outputs.
How to Use This Calculator
- Choose an estimation method suited to your flame type.
- Enter heat release rate and select correct units.
- Measure the steady flame base diameter carefully.
- Add wind, temperature, pressure, and humidity if known.
- Press Calculate to view results above the form.
- Use clearance guidance to plan safe spacing.
- Download CSV or PDF to save your calculation record.
For high winds or very dry conditions, avoid open flames. Follow local burning rules and equipment guidance.
Notes for Garden Use
- Flame height is an estimate, not a guarantee.
- Fuel type and airflow can change results quickly.
- Keep ignition sources away from dry mulch and leaves.
- Maintain clear access to water or an extinguisher.