Resistor Symbols

There are number of resistor components and symbols. Here we are providing overview of standard but also some unusual symbols related to resistive products.

There are two symbols standards used in USA/Japan (NEMA) “zig-zag” style and IEC “new boxed” style used in Europe.

This document provides a comprehensive comparison of resistor symbols across the major international standards used in electrical and electronics circuit diagrams. The three primary standards are IEC 60617 (International Electrotechnical Commission), ANSI Y32.2/IEEE 315 (American National Standards Institute/Institute of Electrical and Electronics Engineers), and ISO 14617 (International Organization for Standardization) [1][2][3].

Understanding these symbol variations is essential for engineers, technicians, and electronics professionals who work with international schematics or collaborate across different regions. While IEC symbols are predominantly used in Europe and internationally, ANSI/IEEE symbols remain common in the United States and parts of Asia [2][3].

Standard Resistor Symbols

International Standards Overview

Resistor symbols in schematics are defined by several international standards bodies, and understanding their scope helps interpret drawings correctly. The three most relevant standards families are:

• IEC 60617 (International) – Graphical symbols for electrotechnical diagrams; widely adopted in Europe and increasingly globally.
• ANSI Y32.2 / IEEE 315 (United States) – Historical US standard for graphic symbols; many libraries still follow it, but the 1975 edition is now classified as an inactive‑reserved standard.
• ISO 14617 (International) – Library of graphical symbols for technical diagrams, harmonized with IEC recommendations and used beyond pure electrical diagrams.

Regional standards such as DIN 40900 (Germany) and AS 1102 (Australia) have largely been superseded by IEC 60617, while modern Japanese JIS standards generally align with IEC conventions.

IEC 60617 Resistor Symbols

The IEC 60617 database defines individual resistor‑related symbols with registration numbers, official names, and application notes. The table below summarizes the most commonly used entries for everyday electronics schematics:

IEC 60617 item*	Official name	Typical use in schematics
Resistor, general symbol	Fixed resistor	Generic resistance element in analog/digital circuits.
Resistor, adjustable	Variable resistor / rheostat	Manually adjustable series resistor in power or control paths.
Resistor with movable contact	Potentiometer	Three‑terminal adjustable divider for voltage or signal level.
Resistor, voltage‑dependent	Varistor / MOV	Surge protection and over‑voltage limiting.
Resistor with fixed tappings	Tapped resistor / attenuator	Pre‑defined ratios for attenuation or bias networks.
Resistor, heating	Heating element	Resistive heater or load with dominant thermal function.
Resistor, current‑sensing	Shunt resistor	Precision low‑value resistor used for current measurement.

*Exact IEC registration numbers are available in the IEC 60617 online database; they depend on subscription and edition.

Resistor (NEMA & IEC Systems)

It is the symbol of a fixed resistor. Both of these symbols represent a fixed resistor in NEMA (left) & IEC (right) standards systems.

Attenuator

An attenuator works opposite to the amplifier. It reduces the power of the signal without distorting it. It dissipates the signal’s power within its own resistor network. The symbol of attenuator is given above. IEC and ISO standards typically represent attenuators as resistor networks with clearly marked tappings or ratios, rather than a unique symbol, so many schematics simply show the underlying resistor network explicitly.

Non Reactive Resistor

These resistors, also known as non-inductive resistors, have pure resistance. A common wire wound resistor has inductance due to the magnetic field produced by the winding. Non-reactive resistors have special winding designs to cancel each other’s magnetic fields.

Impedance

The impedance is a complex quantity made of real & imaginary part. The real part represent the resistance & the imaginary part represents the reactance.

Heating Element

This component converts the electrical energy into heat energy. The current flow through the heating element generates heat energy due to its resistance.

Protective Resistor

These both symbols represent a protection resistor. It operates like a resistor that limits the current flow & if the current exceeds its certain limit then it blow out opening the circuit. In modern designs this function is often implemented with fusible resistors or discrete circuit‑protection devices such as MOVs and PTC resettable fuses, which may use slightly different standardized symbols.

Memristor

Memristor or memory resistor is a non‑volatile component whose resistance depends on the current that has passed through it in the past. In practice, memristor symbols are not yet standardized in IEC 60617; symbol usage is mostly found in research literature and manufacturer‑specific documentation rather than general‑purpose EDA libraries.

Shunt Resistor

A shunt resistor (also known as current shunt) is a resistor with low & precise resistance used to measure the current through it. The current is measured by the voltage drop across it. Thus it acts as a current sensor.

Resistor Array

Resistor array is a combination of multiple resistors in a single packaging. It contains multiple individual resistors denoted by the number in the symbols e.g 8 in this case.  The resistors are not connected together except for its one side which is connected with VCC for pull up & GND for pull down. They are used for saving space & cost of placing.

Variable & Adjustable Resistor Symbols

Variable Resistor

A variable resistor also known as potentiometer or rheostate has a variable resistance. It has three terminals. The two of them have fixed resistance while the third terminal move over the resistive trace or wire to increase or decrease the resistance. They are used for increasing or decreasing  the current flow in a circuit during its normal operation.

Continuous Variable Resistor

Such type of variable resistor has a continuous resistance i.e. the sliding or rotating the contact gives out a continuous value of resistance. It can achieve infinite numbers of resistance values ranging from min to max.

Step Variable Resistor

This type of variable resistor’s resistance increase or decreases in steps . The contacts does not slide smoothly but jumps from steps . Each step movement increase or decrease a fixed amount of resistance.

Carbon Pile Variable resistor

This type of variable resistor is made up of carbon discs clamped together between two metal plates. Increasing or decreasing the pressure between these metal plates increases the resistance of the device.

Variable Resistor with ON/OFF switch

This type of variable resistor has a built-in switch that breaks or make the contact between the two terminals.

Preset Resistor

Preset resistor is a variable resistor that is only operated during manufacturing and tuning a circuit. they are not operated during the normal use of a circuit. there design are not as rigid as a variable resistors (Potentiometer etc).

Special Resistor Symbols

Photo resistor Light Dependent Resistor LDR

It is a light dependent resistor i.e. its resistance depends on the intensity of the light. The resistance of LDR decreases with increase in the light intensity.

Thermistor

Thermistor or thermal resistor is a type of resistor whose resistance depends on its surrounding temperature. It either decrease or increase with the temperature depending on the type of thermistor.

NTC & PTC Thermistor

NTC stands for negative temperature coefficient & PTC stands for positive temperature coefficient. The NTC Thermistor resistance decrease with increase in the temperature & denoted by –t° sign. The PTC thermistor resistance increase with increase in temperature & denoted by +t° sign.

Varistor VDR

Varistor or VDR (voltage dependent resistor) is a type of resistor whose resistance depends on the voltage applied. Its resistance varies with the change in the applied voltage. These symbols (some of them are old & new) represent varistor.

Iron Hydrogen Resistor

It is positive temperature coefficient resistor made of iron wire inside hydrogen filled bulb. Its resistance increase with temperature which is due to the increase in the current flow. The increasing resistance opposes the increase in current. Thus they are used in stabilizing circuit.

Magneto Resistor

Magneto resistor or MDR (Magnetic dependent resistor) is a type of resistor whose resistance depends on the external magnetic field. It resistance changes with change in magnetic field intensity & It is a used as a magnetic sensor for sensing magnetic field.

Resistance thermometer or RTD

Resistance temperature detector (RTD) is a temperature sensor whose electrical resistance changes with the temperature. The material used in RTD’s has very accurate relation between the resistance & temperature. It can be measured by supply of constant current & the voltage drop across the resistor.

Notes on Rare and Historical Symbols

Some resistor‑related symbols in older standards or reference lists—such as iron‑hydrogen resistors, specific “protective resistor” variants, or certain magneto resistor symbols—are rarely used in modern EDA libraries and everyday schematics. Engineers are more likely to encounter them in legacy documentation, historical textbooks, or specialized stabilization and protection circuits than in current PCB design tools.

When documenting new designs, it is usually preferable to use the closest IEC 60617 or ISO 14617 symbol and clearly describe any special functionality (e.g. “fusible resistor”, “magnetic field sensor”) in the component description and notes.

Regional and Historical Variants

1 DIN 40900 (Germany – Obsolete)

The German DIN 40900 standard, now superseded by IEC 60617, used symbols very similar to modern IEC standards, with rectangular representations for fixed resistors and similar arrow indicators for variable types [2].

2. AS 1102 (Australia – Obsolete)

The Australian AS 1102 standard has been replaced by adoption of IEC 60617. Historical Australian schematics may show minor variations in symbol proportions and arrow styles [2].

3 JIS (Japanese Industrial Standards)

Japanese standards generally follow IEC 60617 conventions but with occasional local variations. Some older Japanese schematics may use ANSI-style zig-zag symbols due to historical US influence[2][3].

Symbol Selection Guidelines

Choosing Between IEC and ANSI

International Projects: Use IEC 60617 symbols (rectangular style) for broader international compatibility[2][3]. US-Based Projects: ANSI/IEEE 315 symbols (zig-zag style) remain common in American industry and education[2][3]. Consistency: Never mix IEC and ANSI symbols within a single schematic diagram[2].

Documentation: Always specify which standard is used, typically in the drawing title block [2].

Modern Trends

Current trends show increasing adoption of IEC 60617 symbols globally, even in traditionally ANSI-dominated regions[2][3]. Most modern EDA (Electronic Design Automation) software packages support both standards and allow users to select their preferred symbol set.

In practical design workflows, most mainstream PCB and schematic tools ship with both IEC‑style and ANSI‑style resistor symbols, and project templates often default to IEC for internationally shared designs.[web:9] Whether you work in Altium, KiCad, Cadence, Mentor, or similar environments, it is good practice to select a symbol library at project start and keep that choice consistent across all sheets and revisions.

Reference Designations and Value Notation

Regardless of the symbol standard used, resistor reference designations follow consistent conventions:

• Reference Designator: Always begins with “R” followed by a sequential number (R1,R2, R3, etc.) [3]
• Value Notation: Expressed in ohms (Ω), kilohms (kΩ), or megohms (MΩ) [3]
• Tolerance: Often indicated as a percentage (±1%, ±5%, etc.) [3]
• Power Rating: Specified in watts (W) when critical to design [3]

Example Reference Designation

• R15
• 4.7kΩ ±5%
• 0.25 watts.

Schematic Conventions for Resistor Symbols

Beyond the graphical symbol itself, consistent placement of labels and values is critical for readable schematics. In practice, most organizations follow a few simple conventions:

• Reference designator position – Place the R‑number (e.g. R15) close to and slightly above or beside the symbol, keeping orientation consistent across the drawing.
• Value and tolerance – Place the resistance value and tolerance just below or next to the symbol (e.g. “4.7 kΩ ±5%”), using standardized units (Ω, kΩ, MΩ).
• Power rating indication – When power dissipation is critical, add the nominal power rating (e.g. “0.25 W”) either on the same line as the value or in the component list / bill of materials.
• Networks and arrays – For integrated resistor arrays, use suffixes such as R10A, R10B, R10C to distinguish individual elements within the package while retaining a clear link to the physical part.
• Sensor and dependent resistors – Many schematics keep R‑based designators but add functional hints in the name, such as “RT1” for a thermistor, “LDR1” for a photo resistor, or “VDR1” for a varistor.

These conventions help layout engineers, test engineers, and documentation teams interpret the same drawing without ambiguity, regardless of whether IEC or ANSI symbol shapes are used.

Standards Comparison Summary

Standard	Region	Current status	Symbol style / note
IEC 60617	International	Active (online database)	Rectangle‑based IEC style.
ANSI Y32.2 / IEEE 315‑1975	United States	Inactive‑reserved, still used as legacy reference	Zig‑zag ANSI style, widely seen in older drawings and some current US practice.
ISO 14617	International	Active	Harmonized with IEC; broader technical diagrams.
DIN 40900	Germany	Obsolete	Historical; superseded by IEC 60617.
AS 1102	Australia	Obsolete	Historical; replaced by IEC adoption.
JIS C 0617	Japan	Active	Generally follows IEC 60617 with minor local variations.

Understanding resistor symbol variations across these standards is essential for effective communication in international electronics engineering, especially when documentation and design teams are spread across multiple regions.

Modern engineering practice increasingly favors IEC 60617 symbols for international compatibility, though ANSI/IEEE 315 remains prevalent in US-based work[2][3]. The most critical practice is maintaining consistency within any single schematic and clearly documenting which standard is employed.

Conclusion

Resistor symbols form a graphical language that links component behaviour to schematic representation, and small differences between standards can carry important meaning. For new designs, using IEC 60617 (or closely aligned ISO 14617 / JIS symbols) and documenting that choice in the title block provides the best compatibility across international teams and EDA tools.

When working with legacy schematics, recognising ANSI/IEEE 315 and historical regional variants ensures correct interpretation and avoids mistakes in redesign or maintenance. Above all, consistency within each schematic and clear notation of reference designations, values, and tolerances are more critical than the exact symbol shape chosen.

FAQ – Resistor Symbols

References

• [1] IEC 60617 Symbols Documentation. Available at: https://qelectrotech.org/forum/misc.php?action=punattachment&item=2124
• [2] EEPower. (2024). Resistor Symbols | Resistor Standards and Codes. https://eepower.com/resistor-guide/resistor-standards-and-codes/resistor-symbols/
• [3] Utmel. (2025). Resistor Symbols: From Circuit Diagrams to PCB Design. https://www.utmel.com/blog/categories/resistor/resistor-symbols-from-circuit-diagrams-to-pcb-design
• [4] Passive Components EU. (2026). Resistor Symbols. https://passive-components.eu/resistor-symbols/
• [5] ASUTPP. Resistor Symbols: Complete List. https://www.asutpp.com/resistor-symbols.html
• [6] AiChipLink. (2025). Decoding Potentiometer Symbols in Circuit Diagrams. https://aichiplink.com/blog/Decoding-Potentiometer-Symbols-in-Circuit-Diagrams
• [7] Wikipedia. (2005). Electronic symbol. https://en.wikipedia.org/wiki/Electronic
• [8] IEC 60617: Graphical symbols for diagrams (online database). Subscription information at: https://webstore.iec.ch/publication/60617
• [9] ISO 14617: Graphical symbols for diagrams. Overview at: https://www.iso.org/standard/37844.html