GASAP calculators
Gas rate, combustion air and flue sizing aids for UK gas appliance work — always follow manufacturer instructions and Gas Safe practices.
Gas rate → kW
m³/h × gross CV ÷ 3.6 — typical natural gas CV ≈10.5 kWh/m³ (verify meter/regional data).
Combustion air (indicative)
Flue area (ratio)
Gas pipe sizing
Coming soon
IGE/UP/1 and BS 6891 length / pressure-drop tables — interactive sizing in a future update.
CO / CO₂ ratio
Coming soon
Combustion analyser ratio checker with manufacturer bands — use your FGA on site for now.