Calculator Inputs
Use direct area, rectangular plates, or circular plates. Choose a solve mode and the page will place results above this form.
Plotly Graph
The chart sweeps plate separation and shows how capacitance changes for the solved geometry and dielectric setup.
Example Data Table
| Case | Dielectric | Area | Gap | Voltage | Capacitance |
|---|---|---|---|---|---|
| Lab sensor | Air (εr = 1.0) | 100 cm² | 1 mm | 12 V | 88.54 pF |
| Glass-filled unit | Glass (εr = 5.0) | 150 cm² | 0.5 mm | 24 V | 1.33 nF |
| Insulated test cell | PTFE (εr = 2.1) | 250 cm² | 2 mm | 50 V | 232.42 pF |
Formula Used
Main capacitance relation: C = ε0 × εr × A / d
Charge: Q = C × V
Stored energy: U = 0.5 × C × V²
Electric field: E = V / d
Surface charge density: σ = Q / A
Energy density: u = 0.5 × ε × E²
Here, ε0 is vacuum permittivity, εr is relative permittivity, A is plate area, d is separation, and V is applied voltage.
How to Use This Calculator
- Pick a calculation mode such as capacitance, area, separation, or dielectric constant.
- Select the plate geometry. Enter direct area, rectangular dimensions, or a circular radius.
- Provide spacing, dielectric constant, and voltage using any listed engineering units.
- Enable the fringing estimate when you want a practical edge-effect adjustment.
- Press calculate to place the results, export buttons, and graph above the form.
Frequently Asked Questions
1) What does this calculator return?
It can solve capacitance directly or back-solve required area, separation, or dielectric constant. It also reports charge, stored energy, electric field, surface charge density, and equivalent dimensions.
2) Why does capacitance increase with plate area?
Larger area lets more electric flux link the plates for the same voltage. In the ideal equation, capacitance is directly proportional to area, so doubling area doubles capacitance.
3) Why does a bigger gap reduce capacitance?
Greater separation weakens the electric coupling between plates. Because capacitance is inversely proportional to distance, doubling the gap cuts ideal capacitance to half.
4) What is relative permittivity?
Relative permittivity, also called dielectric constant, shows how strongly a material supports electric polarization compared with vacuum. Higher values increase capacitance when the geometry stays unchanged.
5) Can I model circular plates?
Yes. Choose circular geometry and enter the radius. The page converts that radius into plate area automatically before applying the parallel-plate formulas.
6) What is the fringing option for?
It adds a practical estimate for edge effects where field lines spread near plate boundaries. The ideal formula assumes a perfectly uniform field, so fringing can slightly raise the predicted capacitance.
7) Why are energy and charge so small?
Many capacitors store very small charge and energy unless capacitance or voltage is large. Picofarads and nanofarads naturally lead to nanocoulomb and nanojoule-scale results.
8) Does this tool check dielectric breakdown?
Not directly. It reports electric field, which you can compare with a material’s breakdown strength from a trusted reference. Staying below breakdown remains an engineering safety requirement.