https://www.calculator.net/btu-calculator.html?roomwidth=20&roomwidthunit=feet&roomlength=15&roomlengthunit=feet&ceilingheight=10&ceilingheightunit=feet&insulation=poor&temperature=30&temperatureunit=c&calctype=heat&x=65&y=9
Two free calculators estimate the number of BTUs needed to cool or heat a room or house based on its size, insulation, and some other conditions.
btu calculator
https://heatersize.net/
HeaterSize.net provides expert heating tools to help you accurately calculate the BTU requirements for your space. Use our calculator for heater sizing to...
btu calculatorheatersizeneed
https://www.toolstation.com/help-and-advice/btu-calculator
Work out the heat requirements of any room with our handy BTU calculator.
btu calculatorradiatortoolstation