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.
