Natural gas is generally transferred through steel pipes and can be measured by the pressure it exudes onto a valve at the end of the pipe. This pressure reading is given on most natural gas containers, especially those fitted onto gas grills. British Thermal Units (BTU) is a measure of heat output. In some industrial applications, it is important to calculate the amount of heat output that is possible from a certain natural gas pressure.

Use the caliper to measure (in inches) the diameter of the pipe the pressure reading is taken from.

Use a conversion chart to convert the pressure and pipe size to an MBH value, which stands for 1,000 BTUs per hour. For example, a downstream pressure of 9.0 on a 1/2-inch pipe yields a value of 515 MBH.

Divide the value from Step 2 by 1,000 to convert to BTUs per hour. For example, divide 515 by 1000 to yield .515 BTUs per hour.