Capacitance Converter
Free Capacitance Converter for tech & electronics units. Enter a value to see equivalent measurements across systems.
Capacitance Converter
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Formula: C = Q / V | E = 0.5 x C x V^2 | 1 F = 10^6 uF = 10^9 nF = 10^12 pF
Worked example โ 47 nF = 0.047 uF = 47,000 pF
Formula
C = Q / V | E = 0.5 x C x V^2 | 1 F = 10^6 uF = 10^9 nF = 10^12 pF
Capacitance (C) is the ratio of charge (Q) to voltage (V). The farad is the SI unit, but practical capacitors use sub-units: microfarads (uF = 10^-6 F), nanofarads (nF = 10^-9 F), and picofarads (pF = 10^-12 F). Energy stored equals half the capacitance times voltage squared.
Worked Examples
Example 1: Capacitor Unit Conversion
Problem:Convert a 47 nF ceramic capacitor value to microfarads and picofarads.
Solution:47 nF to uF: 47 / 1000 = 0.047 uF 47 nF to pF: 47 x 1000 = 47,000 pF
Result:47 nF = 0.047 uF = 47,000 pF
Example 2: Energy Storage Calculation
Problem:Calculate the energy stored in a 2200 uF capacitor charged to 25V.
Solution:E = 0.5 x C x V^2 C = 2200 uF = 0.0022 F E = 0.5 x 0.0022 x 625 E = 0.6875 joules
Result:2200 uF at 25V stores 0.6875 joules of energy
Frequently Asked Questions
What is capacitance and what does it measure?
Capacitance measures a component's ability to store electrical charge. It is defined as the ratio of the electric charge stored on a conductor to the voltage across it (C = Q/V). The unit of capacitance is the farad (F), named after Michael Faraday. One farad is the capacitance of a device that stores one coulomb of charge per volt. In practice, most capacitors are measured in microfarads, nanofarads, or picofarads because one farad is an extremely large capacitance.
How do you convert between microfarads, nanofarads, and picofarads?
The conversion follows standard metric prefixes: 1 microfarad (uF) equals 1,000 nanofarads (nF) and 1,000,000 picofarads (pF). Working the other way, 1 nanofarad equals 0.001 microfarads and 1,000 picofarads. To convert, multiply or divide by 1,000 at each step. A useful mnemonic is that each prefix step (pF to nF to uF to mF to F) is a factor of 1,000. So a 4,700 pF capacitor is the same as 4.7 nF or 0.0047 uF.
How much energy does a capacitor store?
The energy stored in a capacitor is calculated with the formula E = 0.5 times C times V squared, where E is energy in joules, C is capacitance in farads, and V is voltage across the capacitor. For example, a 1000 uF capacitor charged to 12 volts stores 0.5 times 0.001 times 144 = 0.072 joules. Energy increases with the square of voltage, so doubling the voltage quadruples the stored energy. This relationship is important for power supply design and safety considerations.
What factors affect the capacitance of a capacitor?
Three main factors determine capacitance: the area of the overlapping plates (larger area means higher capacitance), the distance between the plates (smaller distance means higher capacitance), and the dielectric material between the plates (higher dielectric constant means higher capacitance). The formula is C = epsilon times A divided by d, where epsilon is the permittivity of the dielectric, A is the plate area, and d is the plate separation. This is why different capacitor types use various materials and construction methods to achieve different capacitance ranges.
How do series and parallel connections change total capacitance?
Capacitors behave the opposite way to resistors. In parallel the values simply add, because the effective plate area adds: two 10 uF capacitors in parallel give 20 uF. In series the reciprocals add, 1/C_total = 1/C1 + 1/C2, so the same two 10 uF capacitors in series give 5 uF, less than either one alone. Series stacking is nevertheless useful because the applied voltage divides across the string, letting lower-rated parts survive a higher rail.
What does the three-digit code printed on a small capacitor mean?
Ceramic and film capacitors are too small for a full value, so they use the EIA shorthand where the first two digits are significant figures and the third is the number of trailing zeros, with the result expressed in picofarads. A part marked 104 is 10 followed by four zeros, or 100,000 pF, which is 100 nF or 0.1 uF. Likewise 223 means 22,000 pF, that is 22 nF. Electrolytic and larger film capacitors have room to print the value directly, usually in microfarads.
How much charge does a capacitor actually hold at a given voltage?
Rearranging the defining relationship C = Q/V gives Q = C x V, with charge in coulombs when capacitance is in farads and voltage in volts. A 470 uF electrolytic charged to 12 V holds 0.00047 x 12 = 0.00564 coulombs, or 5.64 millicoulombs. Charge scales linearly with voltage while stored energy scales with the square of it, which is why a bank that seems to hold a modest amount of charge can still deliver a dangerous discharge.
How does capacitance set an RC time constant?
Pair a capacitor with a series resistor and the circuit gains a time constant, tau = R x C, in seconds when resistance is in ohms and capacitance in farads. After one time constant the capacitor has charged to about 63.2 percent of the supply, and after five it is within one percent of it. A 10 kilohm resistor with a 100 uF capacitor gives tau = 1 second. This is the mechanism behind switch debouncing, power-on reset delays and simple RC low-pass filters.
What is capacitive reactance and why does it depend on frequency?
Capacitive reactance is the opposition a capacitor presents to alternating current, Xc = 1 / (2 x pi x f x C), measured in ohms. It falls as either frequency or capacitance rises, so a capacitor blocks DC and passes high frequencies. A 0.1 uF capacitor presents about 1,592 ohms at 1 kHz but only about 1.6 ohms at 1 MHz. That frequency dependence is why decoupling networks pair a large electrolytic for low-frequency bulk with a small ceramic for high-frequency transients.
What is the difference between C0G/NP0 and X7R ceramic dielectrics?
They are different EIA dielectric classes with very different stability. C0G, also written NP0, is a Class 1 dielectric with a near-zero temperature coefficient and almost no loss of value under applied DC bias, which makes it the choice for oscillators, timing networks and precision filters, though it stores little per unit volume. X7R is a Class 2 dielectric offering far more capacitance in the same package, held to plus or minus 15 percent from minus 55 to plus 125 degrees Celsius, but its value can drop substantially under DC bias.
References
Reviewed for accuracy by Manoj Kumar, Mathematics Educator ยท Editorial policy
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