How to use it
- Choose whether you are entering the radius or the diameter, and the unit (mm, cm, m, in, ft).
- Type the radius or diameter and the height. The volume, capacity in litres and gallons and the three surface areas update live.
- Switching between radius and diameter converts the value you typed so the cylinder stays the same.
- Copy the summary or share the link.
Example
Radius 3 cm, height 5 cm: base area π × 3² = 28.27 cm²; volume 28.27 × 5 = 141.37 cm³ = 141.37 ml; side 2π × 3 × 5 = 94.25 cm²; total surface 94.25 + 2 × 28.27 = 150.80 cm². A water tank with a 1.2 m diameter (r = 0.6 m) and 1.5 m height: π × 0.36 × 1.5 = 1.696 m³ = 1,696 L = 448 US gallons.
Formulas
V = π r² h
lateral area = 2 π r h base area = π r² (two bases)
total surface area = 2 π r h + 2 π r² = 2 π r (r + h)
litres = V[m³] × 1,000; US gal = L / 3.785411784; UK gal = L / 4.54609The formulas are for a right circular cylinder (ends perpendicular to the axis). For a tilted (oblique) cylinder the volume is the same if h is the perpendicular height, but the lateral area is larger. Wall thickness is not subtracted – for the capacity of a pipe or tank enter the inside radius. Partially filled horizontal tanks need a segment calculation, which this tool does not do.
Sources: Wolfram MathWorld – Cylinder, NIST – SI units and conversion factors.
Questions
- How many litres does a cylinder hold?
- Work in centimetres: volume in cm³ ÷ 1,000 = litres. A 10 cm radius, 31.83 cm tall cylinder is 10,000 cm³ = 10 L. The tool does this conversion for any unit.
- What is the lateral surface area?
- The curved side only, as if the label were unrolled into a rectangle of width 2πr and height h. Add the two circular ends for the total area – needed for paint, insulation or sheet metal.
- Does the order of radius and height matter?
- Yes. The radius is squared, so a short wide cylinder holds more than a tall narrow one with the dimensions swapped: r = 5, h = 2 gives 157 cm³, r = 2, h = 5 gives 62.8 cm³.