Circuit Symbols
Drawing style

Capacitor symbol

Two equal plates mean a capacitor with no polarity. A polarised capacitor, such as most electrolytics, adds a + mark. In the drawings here the curved US plate is negative and the hollow IEC plate is positive.⁠Source 1Source 2Source 3Source 4Source 5Source 6Source 7Source 8

Reference Designator C⁠Source 9

On this sheet

Symbol and terminals

Fig. 1 — Capacitor, drawn the same in US and IEC style: two plates; terminals 1, 2

Terminals

12
A non-polarised capacitor has two interchangeable terminals.⁠Source 1

Parts of the drawing

  • Polarised capacitor symbol in US style, with numbered leaders to the + mark and the curved plate
1 + mark
In the polarised capacitor drawings here, + marks the positive terminal. The US form has a curved negative plate; the IEC form has a hollow positive plate. The marked polarity must be respected.⁠Source 1Source 8
2 Curved plate
The − terminal is the other side of the marked polarity. In the US form here it connects to the curved plate; in the IEC form, to the plate opposite the hollow one.⁠Source 1Source 8
  • Polarised capacitor symbol in IEC style, with numbered leaders to the + mark and the hollow plate
1 + mark
In the polarised capacitor drawings here, + marks the positive terminal. The US form has a curved negative plate; the IEC form has a hollow positive plate. The marked polarity must be respected.⁠Source 1Source 8
2 Hollow plate
The + terminal is the one the polarity mark names as positive. In the US form here it connects to the straight plate; in the IEC form, to the hollow plate.⁠Source 1Source 8
Fig. 2 — Polarised capacitor symbol, US style, its marks numberedPolarised capacitor symbol, IEC style, its marks numbered
  • Polarised capacitor symbol, US style, turned 0°, with its terminal names attached

    0°

  • Polarised capacitor symbol, US style, turned 90°, with its terminal names attached

    90°

  • Polarised capacitor symbol, US style, turned 180°, with its terminal names attached

    180°

  • Polarised capacitor symbol, US style, turned 270°, with its terminal names attached

    270°

  • Polarised capacitor symbol, US style, mirrored, with its terminal names attached

    Mirrored

Rotating or mirroring a whole symbol, with its terminal identities and connections preserved, does not change the component. The terminal labels move with the drawing.⁠Source 10

  • Polarised capacitor symbol, IEC style, turned 0°, with its terminal names attached

    0°

  • Polarised capacitor symbol, IEC style, turned 90°, with its terminal names attached

    90°

  • Polarised capacitor symbol, IEC style, turned 180°, with its terminal names attached

    180°

  • Polarised capacitor symbol, IEC style, turned 270°, with its terminal names attached

    270°

  • Polarised capacitor symbol, IEC style, mirrored, with its terminal names attached

    Mirrored

Rotating or mirroring a whole symbol, with its terminal identities and connections preserved, does not change the component. The terminal labels move with the drawing.⁠Source 10

Fig. 3 — Polarised capacitor symbol, US style at 0°, 90°, 180° and 270°, and mirroredPolarised capacitor symbol, IEC style at 0°, 90°, 180° and 270°, and mirrored

Variants

  • +−
    +−

    Polarised (polarized) capacitor

    As in Fig. 2, the parts of the drawing.

  • 12

    Variable capacitor

    In the variable-capacitor convention used here, a diagonal arrow through the plates indicates adjustable capacitance.⁠Source 8

Often confused with

    • Cell symbol; ringed: lines differ in length

      Cell

      Lines differ in length

    • Battery symbol; ringed: lines differ in length

      Battery

      Lines differ in length

    • Capacitor symbol; ringed: two plates drawn the same length

      Capacitor

      Two plates drawn the same length

    • Polarised capacitor symbol in US style; ringed: polarity mark, with the ringed part enlarged 3:1 in a detail view

      Polarised capacitor

      Polarity mark

    A cell and a capacitor are both drawn as two parallel lines. In a cell, and in each cell of a battery, the lines differ in length and the long line is the positive terminal; a capacitor's two plates are drawn the same length, and only a polarised capacitor adds a polarity mark.⁠Source 1Source 2Source 3Source 4

    • Cell symbol; ringed: lines differ in length

      Cell

      Lines differ in length

    • Battery symbol; ringed: lines differ in length

      Battery

      Lines differ in length

    • Capacitor symbol; ringed: two plates drawn the same length

      Capacitor

      Two plates drawn the same length

    • Polarised capacitor symbol in IEC style; ringed: polarity mark, with the ringed part enlarged 3:1 in a detail view

      Polarised capacitor

      Polarity mark

    A cell and a capacitor are both drawn as two parallel lines. In a cell, and in each cell of a battery, the lines differ in length and the long line is the positive terminal; a capacitor's two plates are drawn the same length, and only a polarised capacitor adds a polarity mark.⁠Source 1Source 2Source 3Source 4

    Fig. 4 — Cell, battery, capacitor and polarised capacitor, the mark that tells them apart ringedCell, battery, capacitor and polarised capacitor, the mark that tells them apart ringed
    • Variable capacitor symbol; ringed: plates

      Variable capacitor

      Plates

    • Variable resistor symbol in US style; ringed: zigzag

      Variable resistor

      Zigzag

    A diagonal arrow through a symbol marks it as adjustable, whatever the component, so the body under the arrow says what it is: plates for a variable capacitor, a zigzag or rectangle for a variable resistor, a coil for a variable inductor.⁠Source 3Source 4

    • Variable capacitor symbol; ringed: plates

      Variable capacitor

      Plates

    • Variable resistor symbol in IEC style; ringed: rectangle

      Variable resistor

      Rectangle

    A diagonal arrow through a symbol marks it as adjustable, whatever the component, so the body under the arrow says what it is: plates for a variable capacitor, a zigzag or rectangle for a variable resistor, a coil for a variable inductor.⁠Source 3Source 4

    Fig. 5 — Variable capacitor and variable resistor, the mark that tells them apart ringedVariable capacitor and variable resistor, the mark that tells them apart ringed

On the part

  • An aluminium electrolytic capacitor can outline with a stripe down one side carrying minus signs; a package marking, not part of the schematic symbol
1 Stripe
2 − sign
Many electrolytic capacitors are marked for polarity on the part itself, typically with a − sign beside the negative lead, often printed on a stripe down the can. That marking belongs to the part, not the schematic, and it is not uniform: some parts mark the positive terminal instead, and a stripe on a non-polarised film capacitor means something else.⁠Source 7Source 11
Fig. 6 — An aluminium electrolytic can outline, drawn apart from the symbol, with its printed stripe

Where you meet it

  • A capacitor in a loop with a battery and a resistor, drawn with no values
  • A capacitor in a loop with a battery and a resistor, drawn in IEC style with no values
Fig. 7 — A capacitor in a loop with a battery and a resistor; values left offA capacitor in a loop with a battery and a resistor; values left off ⁠Source 9

Notes

Most electrolytics are polarised, but not all

Most electrolytic capacitors are polarised: voltage of the wrong polarity can damage their very thin oxide insulating layer, so they are marked to show their polarity. The two words are not interchangeable, since non-polarised electrolytic capacitors also exist and are usually marked NP.⁠Source 5Source 6Source 7 A polarised part is drawn with the polarised capacitor symbol, whose + names the terminal to keep the more positive.

The + names a terminal; the part’s own marking finds the lead

A capacitor's + mark identifies its positive electrical terminal. A schematic does not specify physical lead length or package pinout; those require the component's own markings and documentation.⁠Source 1Source 10Source 12 The band on a diode works the same way, as the diode symbol page explains for the cathode.

2p2 is 2.2 pF, and 2n2 is 2.2 nF

Capacitor values use the same idea with p and n: 2p2 is 2.2 pF and 2n2 is 2.2 nF. Some makers write R instead on a capacitor, where 2R2 means 2.2 pF rather than 2.2 Ω.⁠Source 13Source 14 Resistor values follow the same letter code: on the resistor symbol page, 4k7 is 4.7 kΩ.

Check your reading

More questions on the practice page

Pick an answer to see the reason.

  1. Question 1

    Which component is this?

    12

    Two parallel vertical lines of equal length, with a lead from the middle of each: labelled 1 on the left and 2 on the right.

    Not this one Right Answer

    The answer is “A capacitor”. In a cell symbol the long thin line is the positive terminal and the short thick line is the negative terminal.In the polarised capacitor drawings here, + marks the positive terminal. The US form has a curved negative plate; the IEC form has a hollow positive plate. The marked polarity must be respected. A cell and a capacitor are both drawn as two parallel lines. In a cell, and in each cell of a battery, the lines differ in length and the long line is the positive terminal; a capacitor's two plates are drawn the same length, and only a polarised capacitor adds a polarity mark.

  2. Question 2

    What does the arrow through this capacitor mean?

    12

    Two parallel vertical lines of equal length with a lead from each, labelled 1 and 2, and a diagonal arrow drawn up through both lines.

    Not this one Right Answer

    The answer is “Its capacitance can be adjusted”. A non-polarised capacitor has two interchangeable terminals.A cell and a capacitor are both drawn as two parallel lines. In a cell, and in each cell of a battery, the lines differ in length and the long line is the positive terminal; a capacitor's two plates are drawn the same length, and only a polarised capacitor adds a polarity mark. In the variable-capacitor convention used here, a diagonal arrow through the plates indicates adjustable capacitance.

  3. Question 3

    The labels on this capacitor are hidden. Is it polarised?

    A straight vertical line on the left and a curved line on the right whose middle bows toward it, with a lead from each and a small plus sign above and to the left of the straight line.

    Not this one Right Answer

    The answer is “Yes: the curved plate and the + mark it”. The − terminal is the other side of the marked polarity. In the US form here it connects to the curved plate; in the IEC form, to the plate opposite the hollow one.Most electrolytic capacitors are polarised: voltage of the wrong polarity can damage their very thin oxide insulating layer, so they are marked to show their polarity. The two words are not interchangeable, since non-polarised electrolytic capacitors also exist and are usually marked NP. In the polarised capacitor drawings here, + marks the positive terminal. The US form has a curved negative plate; the IEC form has a hollow positive plate. The marked polarity must be respected.

  4. Question 4

    Does the + on a schematic tell you which lead of the real capacitor is positive?

    Not this one Right Answer

    The answer is “No: read the marking on the part itself”. A schematic symbol shows how terminals connect, not where they are on a real part. Terminal letters such as E, B and C or A and K do not give lead order or package layout; the part's own documentation does.Many electrolytic capacitors are marked for polarity on the part itself, typically with a − sign beside the negative lead, often printed on a stripe down the can. That marking belongs to the part, not the schematic, and it is not uniform: some parts mark the positive terminal instead, and a stripe on a non-polarised film capacitor means something else. A capacitor's + mark identifies its positive electrical terminal. A schematic does not specify physical lead length or package pinout; those require the component's own markings and documentation.

  5. Question 5

    In this IEC-style drawing, what does the hollow plate mark?

    A narrow hollow rectangle on the left and a straight vertical line on the right, with a lead from each and a small plus sign above and to the left of the rectangle.

    Not this one Right Answer

    The answer is “The positive plate”. The − terminal is the other side of the marked polarity. In the US form here it connects to the curved plate; in the IEC form, to the plate opposite the hollow one.In the variable-capacitor convention used here, a diagonal arrow through the plates indicates adjustable capacitance. The + terminal is the one the polarity mark names as positive. In the US form here it connects to the straight plate; in the IEC form, to the hollow plate.

Answer key

  1. 1

    A capacitor

  2. 2

    Its capacitance can be adjusted

  3. 3

    Yes: the curved plate and the + mark it

  4. 4

    No: read the marking on the part itself

  5. 5

    The positive plate

Questions

Does a capacitor have polarity?
A plain capacitor with two equal plates does not: its two terminals are interchangeable. A polarised capacitor does, and its + terminal is the one to keep more positive.⁠Source 1Source 8
What does the curved line on a capacitor symbol mean?
It is the negative plate of a polarised capacitor in the US form. The IEC form marks the other side instead, by drawing the positive plate hollow. Both put the + on the positive side.⁠Source 1Source 8
How is a variable capacitor drawn?
With a diagonal arrow through the plates. The same arrow through a resistor or a coil also means adjustable, so the body under the arrow says what the part is.⁠Source 3Source 4Source 8

Print and files

Printable symbol sheetPrintable symbol sheet More worksheets

Variants as SVG line art: Polarised (polarized) capacitorPolarised (polarized) capacitor, Variable capacitor

Free to reuse under CC BY 4.0. Credit: Circuit Symbols (circuitsymbols.com). Licence and credit

Sources

16 sources, numbered as cited
  1. ModEL — Components and Symbols, §3.15 (capacitor polarity, pp. 27–28)

    Tony R. Kuphaldt, retrieved 2026-09-22.

  2. ModEL — Components and Symbols, §3.5 (cells and ideal source symbols, p. 12)

    Tony R. Kuphaldt, retrieved 2026-09-22.

  3. DC Electrical Circuit Analysis — resistive devices and schematic ground symbols (pp. 53, 59–64)

    James M. Fiore, Mohawk Valley Community College, retrieved 2026-09-22.

  4. Lessons In Electric Circuits, Vol. V — §9, Circuit Schematic Symbols (pp. 130–139)

    Tony R. Kuphaldt, retrieved 2026-09-22.

  5. ModEL — Capacitors and Capacitive Circuits, §3.6 (electrolytic capacitors, p. 53)

    Tony R. Kuphaldt, retrieved 2026-09-23. Most electrolytic capacitors are considered polarized because applying sufficient DC voltage in the wrong polarity will remove this anodized metal-oxide layer

  6. ECE 2210 Capacitors Lab — electrolytic capacitors (p. 2)

    University of Utah, Department of Electrical and Computer Engineering, retrieved 2026-09-23. Most electrolytic capacitors can only be charged in one polarity. Voltage of the wrong polarity can damage the oxide layer

  7. Capacitor Codes (seminar handout)

    MIT Robotics and Electronics Cooperative, retrieved 2026-09-23. typically have a + or a - printed on the case next to one lead … Non-polar electrolytics do exist, and often have the letters "NP" printed on them.

  8. University Physics, Vol. 2, §8.1 — capacitor representations, Figure 8.9

    OpenStax, Rice University, retrieved 2026-09-22.

  9. Design to Manufacturing Standards — Reference Designators (slide 33)

    Dieter Bergman, IPC, retrieved 2026-09-22. BT battery … CB circuit breaker … DS display, lamp, light emitting diode … RT thermistor

  10. Electrical Schematics, §§1.3.1–1.3.5 — nodes, crossings, references and congruent drawings

    Tufts University, retrieved 2026-09-22.

  11. ModEL — Capacitors and Capacitive Circuits, §5.2 (capacitor labelling and polarity stripes, pp. 70–72)

    Tony R. Kuphaldt, retrieved 2026-09-23. the 3300 microFarad capacitor (center photo) bears a black stripe and “−” symbol pointing toward its negative terminal

  12. General Descriptions of Aluminum Electrolytic Capacitors — reverse polarity, §2-3-2

    Nichicon, retrieved 2026-09-22.

  13. ModEL — Components and Symbols, §4.3 (capacitor labelling, p. 49)

    Tony R. Kuphaldt, retrieved 2026-09-23. a lower-case letter “p” may be used as a decimal point; e.g. 2p2 would be 2.2 picoFarads. Similarly, the lower-case letter “n” may be used as a decimal point as well

  14. IEC 60062:2016+AMD1:2019 — Marking codes for resistors and capacitors; public preview contents (preview p. 3)

    International Electrotechnical Commission, retrieved 2026-09-23. 4 Letter and numeral code for resistance and capacitance values … 4.2.1 The RKM code system … 4.3.1 The multiplier code system for capacitors

  15. ModEL — Semiconductor Logic Gates, §2.1 (schematic versus package pinout, p. 8)

    Tony R. Kuphaldt, retrieved 2026-09-23. Research a manufacturer’s datasheet for this logic gate IC to see the “pinout” diagram showing which pins on the IC package connect to which inverter gate terminals inside.

  16. ModEL — Electromechanical Relays, §§3.2–3.3 and §5.1 (normal and present contact status)

    Tony R. Kuphaldt, retrieved 2026-09-22.