The instrument used to measure rainfall is called a rain gauge. The classic rain gauge consists of a funnel that leads to a measuring tube.
The area of the top of the funnel is 10 times the cross section of the tube. One inch of rain collected on the funnel transfers to 10 inches of rain in the measuring tube. A variation of the standard rain gauge is the tipping bucket rain gauge. The tipping bucket rain gauge features two separate compartments. When one of the compartments receives 0.2 millimeters of rain, the bucket tips and dumps the water into the other compartment. Weighing-type rain gauges simply weigh rain as it falls into a compartment that is situated on a scale.