For ease of calculating, we chose

1) liquid level and 2) tank diameter

as the data items required for input.
If you only know cap height and diameter, just remember this simple relationship:

Liquid Level = Diameter - Cap Height.

If you need a calculator that will accept other input units, then click here.

The total volume of a partially-filled spherical tank equals total sphere volume minus
spherical cap volume.

To see other *formulas* for a partially-filled spherical tank, click here.

Of course you really don't need those formulas because this calculator does all the work for you.