Decibels relative to full scale, commonly abbreviated dBFS, measures decibel amplitude levels in digital systems such as pulse-code modulation (PCM) which have a defined maximum available peak level. Similar units are dBov and dBO.
0 dBFS is assigned to the maximum possible digital level. For example, a signal that reaches 50% of the maximum level at any point would reach −6 dBFS at that point, 6 dB below full scale. Conventions differ for RMS measurements, but all peak measurements will be negative numbers, unless they reach the maximum digital value.
A digital signal that does not contain any samples at 0 dBFS can still clip when converted to analog due to the signal reconstruction process interpolating between samples. This possibility can be prevented by careful digital-to-analog converter circuit design.