How to Use This Tool
This calculator determines the total liquid capacity of an empty or filled cylindrical vessel—such as a fermentation tank, drum, or storage bin—based on its physical dimensions.
Radius: Determine the radius of your tank by measuring the diameter (the total width), divide that number by two.
Height: Measure the vertical distance of the tank or liquid. You can enter this directly in Option A (if the tank is empty), or use Option B (if the tank has been filled) to calculate it by measuring from the top of the tank down to the liquid level.
Precision: For the most accurate results, use internal measurements to account for the thickness of the tank walls.
If your tank is already partially full, use Option B to find the exact volume of liquid currently inside without needing to empty the vessel.
Total Tank Height: Measure the exterior height of the tank from the floor (or the interior bottom) to the very top rim.
Empty Space (Ullage): Measure the distance from the top rim down to the surface of the liquid.
The Result: The calculator automatically subtracts the empty space from the total height to find your "Liquid Depth." It then uses your Radius to determine the total gallons currently held.
The Math: Why 231?
In the United States, a standard liquid gallon is defined as exactly 231 cubic inches. This tool first calculates the volume of your cylinder using the geometric formula
$$V = \pi r^2 h$$
and then converts those cubic inches into gallons by dividing by the 231 constant.
Winemaker’s Tip: Headspace
When calculating for fermentation, always remember to leave "headspace." Most pros aim for a tank capacity that is 10% to 20% larger than the actual liquid volume to prevent overflows during active fermentation.