We test the suitability of hand clap recordings for measuring several acoustic features of musical performance and recording rooms. Our goal is to make acoustic measurement possible for amateur musicians and hobbyists through the use of a smartphone or web app. Hand claps are an attractive acoustic stimulus because they can be produced easily and without special equipment. Hand claps lack the high energy and consistency of other impulse sources, such as pistol shots, but we introduce some signal processing steps which mitigate these problems to produce reliable acoustical measurements. Our signal processing toolchain is fully-automated, which allows both amateurs and technicians to perform measurements in just a few seconds. Using our technique, measuring a room's reverberation times and frequency response is as easy as starting a smartphone app and clapping several times.