Enter this in field marked RADIUS below. A roll of toilet paper because why not. Find the height of the cylinder.
Multiply the area of the base by the height.
Enter the radius and height and press Calculate. Sometimes you will know the volume and the base area of a cylinder and you wont know the height of it. To calculate the volume of a cylinder we need to know the radius of the circular cross-section of the cylinder - this is the measurement from the centre of the circle to the outer-edge. The base is equal to a circle so you use the area of a circle formula to find the area of the base.