The Gas Rating Slide Rule pocket guide provides essential technical advice and quick reference slide rules for gas meters with a maximum capacity of 6m³/h (metric) or 212ft³/h (imperial).

The pocket guide has 2 slide rules, one for gas meters that use a metric scale (m³/h) and one for gas meters that use imperial scale (ft³/h), which when combined with the gas consumption - measured at the gas meter - of the appliance, will give the heat input of the appliance in both net and gross terms.