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Gas Rate Calculator
Calculate the gas input rate (kW) from the gas flow rate and calorific value. Essential for Gas Safe engineers when commissioning and servicing boilers and gas appliances.
How to Calculate Gas Rate
Gas input rate (kW) = Gas Flow (m³/h) × Calorific Value (MJ/m³) ÷ 3.6. The calorific value of natural gas in the UK is typically 37–40 MJ/m³.
Gas Safe engineers measure the gas flow rate using a U-tube manometer or gas meter clocking method, then calculate the input rate to verify the appliance is correctly rated.
Frequently Asked Questions
What is the calorific value of natural gas in the UK?
UK natural gas typically has a calorific value of 37–40 MJ/m³, with 38.7 MJ/m³ commonly used for calculations. Check your gas supplier's declared value.
How do I measure gas flow rate?
Use a U-tube manometer at the gas valve test point, or clock the gas meter (time how long it takes to consume a known volume). Convert the reading to m³/h for this calculator.
Gas Rate Calculator
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