dBFS (decibels relative to Full Scale) measures digital level against the loudest value the format can store, which is defined as 0 dBFS. Everything below sits at a negative number, so a sample peaking at -6 dBFS uses half the available voltage range. It is a sample-domain measure: a peak meter reads the highest sample, period. That makes dBFS exact but slightly optimistic, because the analog waveform reconstructed by the DAC can rise between samples above the highest stored value — the inter-sample peaks that true-peak (dBTP) metering catches. Use dBFS to watch headroom and avoid clipping; use dBTP for delivery ceilings.
The book · Volume 4 of 7
Audio for Video: A Complete Guide to Sound in Video Products: From PCM and Codecs to Loudness, Accessibility, and Real-Time Voice Processing
dBFS is the scale every digital meter uses, and confusing it with loudness is a common reason mixes pass peak checks and still sound too loud. Volume 4 covers dBFS in detail: digital level and headroom, bit depth and dynamic range, peak versus true peak, and LUFS loudness measurement. Written by Nikolay Sapunov, CEO at Fora Soft.
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