To perform calculation you must provide the tank size, angle and liquid level.
Liquid level measurement
You must measure liquid level at middle line of the tank perpendicular to the bottom of the tank. (see picture). You may measure liquid level at any distance from on of the base (If you do, you must enter the distance in a special parameter).
Alternatively you may tilt the tank to make the zero liquid level at the top base, in this case you must measure tilt angle only.
You may find calculation details and formulas below the calculator.