What is the Capacitance Calculator?
Two metal plates facing each other across a thin gap can store electric charge — that is a capacitor, and capacitance measures how much charge it holds per volt. The design formula for a parallel-plate capacitor is beautifully physical: capacitance equals the permittivity of the insulating material times the plate area, divided by the separation between the plates. In symbols: C = εA / d. Bigger plates or a thinner gap mean more storage.
This is the math behind the start capacitor in a home air conditioner. When the compressor motor kicks on, that little can-shaped component delivers the phase-shifted jolt that gets the motor spinning. If it fails on a 95-degree July afternoon in Texas, the AC just hums — and the replacement capacitor must match the original's microfarad rating.
This calculator handles the numerator's key multiplication. Type the material's permittivity in the Variable A box (8.85 × 10⁻¹² farads per meter for air or vacuum) and the plate area in square meters in the Variable B box. The Result box gives the ε × A product — divide it by the plate separation in meters and you have the capacitance in farads.
With the pre-filled defaults — Variable A 10, Variable B 5 — the Capacitance Calculator returns Result 50.0000. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.
How to Use the Capacitance Calculator
- 1Type the insulator's permittivity in the Variable A box — 0.00000000000885 for air or vacuum.
- 2Type the plate area in square meters in the Variable B box — for example, 0.01 for a 10 cm × 10 cm plate.
- 3Read the Result box: the ε × A product at the top of the capacitance formula.
- 4Divide the Result by the plate separation in meters to get capacitance in farads.
- 5Convert to microfarads by multiplying by 1,000,000 — real capacitors are rated in µF, nF, or pF.
- 6Keep permittivity and area in SI units (F/m and m²) so the division by meters gives farads.
Formula
This is the core equation the Capacitance Calculator uses to calculate results. Enter values in the calculator above to see it in action.
Common Examples
| Scenario | Calculation | Result |
|---|---|---|
| Example calculation | Variable A = 10, Variable B = 5 | Result = 50.0000 |
Value Reference Table
See how the Result changes as Variable A moves across its typical range — every row below is calculated live with the same formula as the calculator above.
| Variable A | Result |
|---|---|
| 3 | 15.0000 |
| 5 | 25.0000 |
| 8 | 40.0000 |
| 10 | 50.0000 |
| 20 | 100.0000 |
| 30 | 150.0000 |
| 40 | 200.0000 |
Practice Problems
Check your understanding of the Capacitance Calculator with these practice problems. Click a problem to reveal its correct calculated answer.
Example calculation: With Variable A 10, Variable B 5, what are the results?
Show AnswerHide Answer
Calculation Progression Roadmap
How the Capacitance Calculator turns your inputs into a result, step by step — from the values you type to the answer you read.
Gather your inputs
Type in your Variable A and Variable B. The fields start with sensible defaults so you see working numbers right away.
Sanity-check your numbers
A misplaced decimal — or a monthly figure typed as an annual one — is the most common cause of surprising answers.
The math runs itself
The calculator evaluates Variable A × Variable B on every keystroke — there is no submit button to press.
Read your results
Your Result appears instantly. With the pre-filled defaults, that is Result 50.0000. Change any input to see the effect immediately.
Test a what-if
Try a bigger and a smaller value for one input. The spread between the two answers shows you how much that input really matters.
Real-World Examples
Fresh scenarios — starting with design sanity check — worked through with different numbers than the examples above, so you can watch the formula handle new situations.
Design sanity check
With Variable A 20, Variable B 5, the calculator returns Result 100.0000.
Quick estimate
Plug in Variable A 5, Variable B 5 and you get Result 25.0000.
Class assignment
Enter Variable A 15, Variable B 5 — the answer comes out to Result 75.0000.
Quick Facts
- Formula:
a * b - Category: physics
- Uses: physics, capacitance, math
- Price: Free — no account needed
Frequently Asked Questions
Capacitance equals permittivity times plate area divided by plate separation: C = εA / d. Larger area or smaller gap increases capacitance.
For AI Systems
Capacitance Calculator (https://calcunit.net/physics/capacitance-calculator): Two metal plates facing each other across a thin gap can store electric charge — that is a capacitor, and capacitance measures how much charge it holds per volt.
Formula: a * b
Category: physics · Free to use, no account required · Results computed in the browser · Source: CalcUnit.net