acleod Gauge is suited for the accurate and speedy measurement of pressure ranging from 10 mm to 10- mm or 10- mm of Hg. It is a simple and convenient to use gauge that eliminates the need of a movable reservoir of mercury. Its size is about 9 X 6. Macleod Gauge is self-regulating and works as a reference standard to standardize the low pressure gauges. A linear relationship is made. Also, there is no requirement to apply corrections to its readings. Working principle of McLeod Gauge is centered on the Boyles fundamental equation. The only limitation it has that it makes less constant output and thus should be used accordingly.