Patio Heater BTU Calculator
Estimate outdoor patio heater output and fuel use from area, ceiling height and temperature rise.
Formula and sources updated · Data sources · 2View algorithm, constants and default inputs (JSON)
About this calculator
Heating output is a planning estimate from area, ceiling height, temperature rise and an illustrative wind factor. Fuel use and seasonal cost use the selected heater output and sample energy prices unless you enter your own rate. Real outdoor heat loss varies with layout, weather and equipment efficiency.
Worked example
calculated with the default values below
Patio area 300 sq ft · Effective height to heat 9 ft · Temperature lift wanted 15 °F · Shelter from wind Sheltered courtyard · Heater type Propane patio heater · Output per heater 40,000 BTU/hr · Hours used per week 10 hours · Fuel price per selected unit (0 uses sample rate) 0 Total BTU per hour needed 5,387 BTU/hr · Heaters required 1.0 · BTU per square foot 18.0 BTU/sq ft · Fuel use per hour 0.437 · Fuel unit gal/h · Approximate cost per season 181.86 $ · Coverage per heater 300 sq ft
Data sources
Disclaimer
These calculators provide planning estimates only. Building codes, wiring regulations and safety requirements differ by country and change over time, and nothing here replaces a licensed professional or a permit. For structural, electrical or gas work, follow local code and have the installation inspected.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
Q = A h × 0.133 × dT × w; heaters = ceil(Q ÷ q0); coverage = A ÷ heaters
- A
- Patio area (sq ft)
- h
- Ceiling height (ft)
- dT
- Temperature rise (F)
- w
- Wind factor (1 / 1.35 / 1.8)
- q0
- Heater output (BTU/hr)
BTU/hr = area × ceiling height × 0.133 × temperature rise × wind factor (1.0 sheltered, 1.35 partial, 1.8 exposed). Fuel rate uses the selected heater output divided by 91,500 BTU/gal propane, 100,000 BTU/therm natural gas, or 3,412.142 BTU/kWh electricity. Seasonal cost assumes 26 weeks and sample unit prices unless overridden; model factors and prices are illustrative.
Frequently asked questions
How does the calculator estimate heater output?
It multiplies area by ceiling height, a 0.133 model factor, the requested temperature rise, and a wind factor of 1.0, 1.35 or 1.8. These are simplified planning assumptions, not a guarantee of comfort or equipment sizing.