Bath volume minus shower flow × minutes.
Bath baseline 150 L fill vs shower 9.5 L/min. Positive difference = water saved vs a bath; negative = a long shower beats a bath on volume.
Shower uses ≈ 114.0 L · vs bath 150 L
Difference (bath − shower) = 36.0 L → shower saves water vs filling the tub.
Human-readable impact: You avoid about 1.80 refills of a 20 L jug compared with filling the tub once.
Shower vs Bath Water Calculator helps you bath volume minus shower flow × minutes. It is commonly used by engineers, lab users, field operators for shower vs bath water, save water shower, bath liters.
Formula
Difference (liters) = 150 L bath − (9.5 L/min × minutes). Positive means the shower uses less than filling the tub.