Mix Bus Level Calculator

When you sum multiple audio tracks onto a single bus, their levels don't just add — for equal-level, uncorrelated signals, summed power scales with the number of tracks, which works out to a level rise of 10*log10(n) decibels. Doubling the track count doubles the summed power and adds a fixed +3.01 dB, not a doubling of level and nowhere near a tripling; going from 1 track to 4 (double the doubling) adds +6.02 dB, and it takes 10 tracks summing before you pick up a full +10 dB. This calculator applies that summation law twice: once to your average track level across the full track count to estimate the bus's overall summed output level, and once to the loudest individual track (capped at a contribution from at most 4 tracks, since only a handful of the loudest simultaneous tracks meaningfully drive the peak) to estimate the realistic peak level hitting the bus. From that peak estimate, it works backward to a suggested fader adjustment: it takes your target headroom in dB below 0 dBFS as the goal peak, subtracts the estimated current peak, and the difference is how many dB to pull the bus fader up or down to land your peaks at that target headroom.

Headroom achieved at current levels is just the negative of the summed level, showing how much space is left before clipping if you don't touch the fader at all. Average bus level per subgroup applies the same log-summation to however many tracks land on each bus (tracks divided evenly across your bus count, rounded up), useful when deciding how much headroom to leave on drum, vocal, or instrument submixes before they hit the master. The core assumption throughout is that tracks are reasonably independent and not perfectly phase-correlated; a mix with doubled unison parts or heavy parallel processing will sum louder in reality than this uncorrelated-signal estimate predicts.