Capacitor Calculator

Calculate series and parallel capacitor combinations, reactance, stored energy, and charge.

Capacitor Configuration

1/Ct = 1/C1 + 1/C2 + ...

Capacitor Values

Voltage (V)

Frequency (Hz)

Series Total

56.897 uF

5.6897e-5 F

Capacitor Values (3)

C1100 uF

C2220 uF

C3330 uF

Calculated Values

Reactance @ 1000 Hz2.80 ohms

Stored Energy4096.5517 uJ

Stored Charge682.7586 uC

Capacitor Formulas

Xc = 1/(2 x pi x f x C)

E = 0.5 x C x V^2

Q = C x V

I = C x dV/dt

What Is a Capacitor?

A capacitor is an electronic component that stores electrical energy in an electric field. It consists of two conductive plates separated by an insulating material (dielectric). Capacitors are fundamental to filtering, timing, coupling, and energy storage in electronic circuits.

Property	Symbol	Unit	Description
Capacitance	C	Farad (F)	Ability to store charge
Voltage rating	V	Volts (V)	Maximum safe voltage
Charge	Q	Coulombs (C)	Stored electrical charge
Energy	E	Joules (J)	Stored energy
ESR	—	Ohms (Ω)	Equivalent series resistance
Tolerance	—	Percent (%)	Value accuracy

Basic Capacitor Formula

Q = C × V (Charge stored) C = Q / V (Capacitance) V = Q / C (Voltage)

Where:

C= Capacitance in Farads
Q= Charge in Coulombs
V= Voltage in Volts

Capacitance Units and Prefixes

The Farad is a very large unit. Practical capacitors are measured in smaller subunits.

Unit	Symbol	Value in Farads	Typical Use
Farad	F	1	Supercapacitors, energy storage
Millifarad	mF	10⁻³ F	Large power supply caps
Microfarad	µF	10⁻⁶ F	Power filtering, audio coupling
Nanofarad	nF	10⁻⁹ F	Signal filtering, timing
Picofarad	pF	10⁻¹² F	RF circuits, high frequency

Conversions: 1 µF = 1000 nF = 1,000,000 pF. When reading capacitor markings, context determines the unit used.

Capacitors in Series and Parallel

Capacitors combine opposite to resistors: parallel adds directly, series uses reciprocals.

Configuration	Formula	Result	Voltage Handling
Parallel	C_total = C₁ + C₂ + C₃ + ...	Sum of all values	Same as lowest rated
Series (2 caps)	C_total = (C₁ × C₂) / (C₁ + C₂)	Less than smallest	Voltages add up
Series (n equal)	C_total = C / n	Value divided by count	n × single voltage
Series (general)	1/C_total = 1/C₁ + 1/C₂ + ...	Use reciprocals	Voltages add

Key insight: Parallel increases capacitance (more charge storage). Series decreases capacitance but increases voltage rating. This is opposite of resistors!

Series/Parallel Formulas

Parallel: C_total = C1 + C2 + C3 + ... Series: 1/C_total = 1/C1 + 1/C2 + 1/C3 + ...

Where:

C1, C2, C3= Individual capacitor values
C_total= Combined equivalent capacitance

RC Time Constant

The RC time constant (τ) defines how quickly a capacitor charges or discharges through a resistor. After one time constant, the capacitor reaches ~63% of full charge.

Time Constants (τ)	Charging (%)	Discharging (%)	Practical Meaning
1τ	63.2%	36.8%	First significant change
2τ	86.5%	13.5%	Mostly charged/discharged
3τ	95.0%	5.0%	Nearly complete
4τ	98.2%	1.8%	Essentially complete
5τ	99.3%	0.7%	Considered fully charged

RC Time Constant

τ = R × C V(t) = V₀ × (1 - e^(-t/τ)) [charging] V(t) = V₀ × e^(-t/τ) [discharging]

Where:

τ (tau)= Time constant in seconds
R= Resistance in Ohms
C= Capacitance in Farads
e= Euler's number (~2.718)

Energy Storage in Capacitors

Capacitors store energy in their electric field. The stored energy depends on capacitance and voltage squared.

Capacitor Type	Typical Capacitance	Voltage Range	Energy Storage
Ceramic (small)	1 pF - 100 nF	10-1000V	Microjoules
Film	1 nF - 100 µF	50-2000V	Millijoules
Electrolytic	0.1 µF - 100,000 µF	6.3-450V	Millijoules to Joules
Supercapacitor	0.1 F - 3000 F	2.5-5.5V	Joules to Kilojoules

Capacitor Energy Formula

E = ½ × C × V² E = ½ × Q × V E = Q² / (2 × C)

Where:

E= Energy in Joules
C= Capacitance in Farads
V= Voltage in Volts
Q= Charge in Coulombs

Types of Capacitors

Different capacitor technologies suit different applications based on capacity, voltage, frequency, and stability requirements.

Type	Capacitance Range	Voltage	Best For	Polarity
Ceramic (MLCC)	1 pF - 100 µF	6.3-5000V	Bypass, high frequency	Non-polar
Film (polyester/polypropylene)	1 nF - 100 µF	50-2000V	Audio, timing, filters	Non-polar
Aluminum electrolytic	0.1 µF - 1 F	6.3-450V	Power supply filtering	Polar
Tantalum	0.1 µF - 1000 µF	2-50V	Compact, stable	Polar
Supercapacitor (EDLC)	0.1-3000 F	2.5-5.5V	Energy storage, backup	Polar
Mica/Silver mica	1 pF - 10 nF	100-1000V	RF, precision circuits	Non-polar

Capacitive Reactance (AC Circuits)

In AC circuits, capacitors have capacitive reactance (Xc)—an opposition to current that decreases with frequency. Unlike resistance, reactance doesn't dissipate power.

Frequency	Reactance	Current Flow	Behavior
DC (0 Hz)	Infinite	Zero (after charging)	Open circuit
Low frequency	High	Low	Blocks low frequencies
High frequency	Low	High	Passes high frequencies
Very high frequency	Very low	Very high	Nearly short circuit

Capacitive Reactance Formula

Xc = 1 / (2πfC) Xc = 1 / (ωC) where ω = 2πf

Where:

Xc= Capacitive reactance in Ohms
f= Frequency in Hertz
C= Capacitance in Farads
ω= Angular frequency (rad/s)

Worked Examples

Calculate RC Time Constant

Problem:

A 10 µF capacitor is connected to a 10 kΩ resistor. What is the time constant, and how long until 99% charged?

Solution Steps:

1Identify values: C = 10 µF = 10 × 10⁻⁶ F, R = 10 kΩ = 10,000 Ω
2Calculate τ: τ = R × C = 10,000 × 10 × 10⁻⁶
3τ = 0.1 seconds = 100 milliseconds
499% charge occurs at approximately 5τ
5Time to 99% = 5 × 0.1 = 0.5 seconds

Result:

τ = 100 ms; reaches 99% charge in 500 ms (0.5 seconds)

Combine Capacitors in Parallel

Problem:

What is the total capacitance of 100 µF, 47 µF, and 22 µF capacitors in parallel?

Solution Steps:

1Parallel formula: C_total = C₁ + C₂ + C₃
2Substitute values: C_total = 100 + 47 + 22
3Calculate: C_total = 169 µF
4Voltage rating: Use the lowest rated capacitor's voltage

Result:

169 µF total capacitance

Calculate Energy Stored

Problem:

How much energy is stored in a 1000 µF capacitor charged to 50V?

Solution Steps:

1Energy formula: E = ½ × C × V²
2Convert: C = 1000 µF = 0.001 F
3Substitute: E = ½ × 0.001 × 50²
4Calculate: E = 0.5 × 0.001 × 2500
5E = 1.25 Joules

Result:

1.25 Joules stored energy

Tips & Best Practices

✓Parallel capacitors add (C_total = C1 + C2); series capacitors use reciprocals—opposite of resistors!
✓The RC time constant τ = R × C gives the time to reach 63% charge; 5τ is essentially fully charged.
✓Electrolytic capacitors are polarized—connect negative to ground or lower voltage side.
✓For power supply filtering, use low-ESR capacitors near switching regulators.
✓Energy stored is proportional to V²—doubling voltage quadruples stored energy.
✓Capacitor value codes work like resistors but in picofarads: '104' = 100nF = 0.1µF.
✓Capacitors block DC but pass AC—the higher the frequency, the lower the reactance.

Frequently Asked Questions

In parallel, capacitors share the voltage but store more total charge (like adding tank capacity). In series, each capacitor only sees part of the charge, reducing effective storage. Resistors work opposite because they divide current (parallel) or voltage (series) in different ways. Think of parallel capacitors as bigger plates, and series as thicker dielectric.

The dielectric can break down, causing the capacitor to short-circuit, leak, bulge, or explode (especially electrolytics). Always use capacitors rated for at least 20-50% above your maximum expected voltage. For safety-critical applications, use an even larger margin. Never exceed the voltage rating, even momentarily.

Only polarized capacitors (electrolytic, tantalum) require correct polarity. Reversing polarity causes rapid degradation, heating, and potential explosion. Ceramic, film, and mica capacitors are non-polarized and can be connected either way. Check markings: electrolytics show negative stripe; tantalum show positive marking.

Equivalent Series Resistance (ESR) is the internal resistance of a capacitor. High ESR causes energy loss as heat and reduces filtering effectiveness, especially at high frequencies. Low-ESR capacitors (polymer, high-quality electrolytics) are essential for power supply filtering and switching converters. ESR increases as capacitors age.

Small capacitors often use a 3-digit code similar to resistors. The first two digits are significant figures, the third is the multiplier (number of zeros) in picofarads. So '104' = 10 × 10⁴ pF = 100,000 pF = 100 nF = 0.1 µF. A letter after indicates tolerance (J=5%, K=10%, M=20%).

Capacitor performance changes with temperature. Higher temperatures reduce lifespan (electrolytic life halves every 10°C above rating) and may change capacitance. Temperature ratings like 85°C or 105°C indicate maximum operating temperature. For automotive or industrial use, choose higher temperature ratings. Ceramic capacitors also have temperature coefficient classes (C0G, X7R, Y5V) indicating stability.

Sources & References

Electronics Tutorials - Capacitors (2024)
All About Circuits - Capacitors (2024)
Vishay Capacitor Application Notes (2024)
Murata Ceramic Capacitor Basics (2024)

Last updated: 2026-01-22

Capacitor Calculator

Capacitor Configuration

Series Total

Capacitor Values (3)

Calculated Values

Capacitor Formulas

What Is a Capacitor?

Basic Capacitor Formula

Capacitance Units and Prefixes

Capacitors in Series and Parallel

Series/Parallel Formulas

RC Time Constant

RC Time Constant

Energy Storage in Capacitors

Capacitor Energy Formula

Types of Capacitors

Capacitive Reactance (AC Circuits)

Capacitive Reactance Formula

Worked Examples

Calculate RC Time Constant

Combine Capacitors in Parallel

Calculate Energy Stored

Tips & Best Practices

Related Calculators

Frequently Asked Questions

Sources & References