Port Tuning Calculator

Formulas cross-validated against independently published worked examples before this tool was built — see data/port-tuning-calculator-formulas.md for sources. All math runs in metric internally and converts for display; several "imperial unit" versions of this formula found online use inconsistent constants, so don't trust one pulled from elsewhere without re-deriving it.

Box & Target Tuning

Net internal box volume

Not sure what your net volume actually is? Use the Net Volume Helper first — this needs net airspace, not your box's outside dimensions.

ft³ liters

Target tuning frequency (Hz) Number of ports

Port shape

Round Slot / rectangular

Port diameter

inches cm

Port end condition

One flanged, one free (typical — flush at the box face, open inside) Both ends flanged Both ends free (rare)

Result

Fill in the box volume, target tuning, and port dimensions, then hit Calculate.

Reverse check: I already built a port — what's my real tuning?

Useful if you rounded your cut length to the nearest 1/8" and want to know the actual resulting Fb.

Net box volume (ft³) Port diameter (in, round port only) Actual physical port length (in)

End condition