Enter your cylindrical capacitor's Inner Radius (a), Outer Radius (b), Length (L), and Relative Permittivity (εr) into the Cylindrical Capacitor Calculator to find the Capacitance — including Capacitance per Unit Length and the full value in Farads.
Capacitance
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Capacitance per Unit Length
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Capacitance (Farads)
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A cylindrical capacitor consists of two coaxial cylindrical conductors separated by a dielectric material. The inner cylinder acts as one plate and the outer cylinder as the other plate, creating an electric field between them.
The capacitance is calculated using the formula C = 2πε₀εᵣL/ln(b/a), where ε₀ is the permittivity of free space, εᵣ is the relative permittivity, L is the length, a is the inner radius, and b is the outer radius.
All dimensions (inner radius, outer radius, and length) should be entered in meters. The calculator will automatically convert the final capacitance result to picofarads for easier reading.
Relative permittivity is the dielectric constant of the material between the conductors. For air or vacuum, use εᵣ = 1. Common materials have higher values: paper (3-4), plastic (2-3), ceramic (up to 1000).
The outer radius must be larger than the inner radius for a valid cylindrical capacitor geometry. If b ≤ a, the configuration is physically impossible and would result in mathematical errors in the logarithmic calculation.
Cylindrical capacitors are commonly used in coaxial cables, high-voltage applications, and RF circuits where the cylindrical geometry provides good shielding and uniform electric field distribution.
Capacitance is directly proportional to the length of the cylindrical conductors. Doubling the length doubles the capacitance, making it easy to scale the design for specific capacitance requirements.