Water tank capacity calculator

Capacities use the exact definitions 1 litre = 1000 cm³, 1 US gallon = 3.785411784 L and 1 imperial gallon = 4.54609 L, which is why the two gallon figures differ by about a fifth. Volume and depth diverge on a horizontal cylinder, a capsule or a cone because those shapes do not widen evenly, which is the whole point of the dipstick chart. What this tool does not do: it assumes a flat-bottomed tank sitting level, it ignores wall thickness, internal fittings and thermal expansion, and a fill above the rim is refused rather than clamped.