Quick answer
They are the same shape. "Quarter cylinder" describes the geometry, "corner cylinder" describes where it goes. Both have two straight sides equal to the radius and a quarter-circle front, and both use V = π × r² × H ÷ 4.Shape differences
Identical. Two straight panels at 90 degrees and a curved panel forming a quarter of a circle. Some manufacturers also call it a quarter round.
Measurement differences
Measure one straight wall side as the radius and the inside height. Both sides should be equal.
Formula differences
V = π × r² × H ÷ 4 for both names.
Which calculator should you use?
Use the corner cylinder calculator. If the two straight sides are different lengths, or the front curve does not meet the walls at right angles, the tank is a corner bow front instead.
Example comparison
Quarter cylinder, 20 in radius, 24 in tall
32.6 gal (123.5 L)
Corner cylinder, 20 in radius, 24 in tall
32.6 gal (123.5 L)
Same inputs, same result, same calculator.