What Is the Difference Between a Transformer and an Inductor?

ElecSuppliers Electronics GuideAug 12, 2026

Transformers and inductors are both magnetic components used in electronic circuits, and their construction can look similar. Both can use magnetic cores and copper windings, but they perform different functions.

A transformer mainly transfers electrical energy between windings and can change voltage or provide electrical isolation. An inductor stores energy in its magnetic field and is commonly used to control current, filter noise and smooth power supply outputs.

Understanding the difference helps when selecting magnetic components for power supplies and other electronic equipment.

What Is a Transformer?

A transformer normally has at least two electrically separate windings: a primary winding and a secondary winding.

An alternating voltage applied to the primary winding creates a changing magnetic field in the core. This changing magnetic field induces a voltage in the secondary winding.

By changing the turns ratio between the primary and secondary windings, a transformer can increase or decrease AC voltage.

Transformers are commonly used in power supplies, isolation circuits, audio equipment, industrial equipment and power conversion systems.

What Is an Inductor?

An inductor is normally built with a single winding around a magnetic core, although its construction can vary depending on the application.

When current flows through the winding, energy is stored in the resulting magnetic field. The inductor resists rapid changes in current and can therefore be used for filtering and energy storage.

Power inductors are widely used in DC-DC converters, switching power supplies, automotive electronics and energy storage systems.

The Main Functional Difference

The biggest difference is how the two components are used.

A transformer transfers energy from one winding to another through magnetic coupling. It can also provide electrical isolation and voltage conversion.

An inductor stores and releases magnetic energy within its own magnetic circuit and is mainly used to control current or filter electrical signals.

Although both use magnetic fields, their circuit functions are different.

Difference in Windings

Transformers normally have two or more windings.

The primary winding receives energy from the input circuit, while the secondary winding transfers energy to another circuit.

An inductor generally has one main winding.

Some magnetic components have multiple windings and can perform functions that overlap between transformers and coupled inductors, so the circuit application and design purpose are important when identifying the component.

Difference in Energy Transfer

A transformer transfers energy between electrically isolated windings.

The amount of voltage generated in the secondary winding depends on the turns ratio and the changing magnetic flux.

An inductor does not normally transfer energy between separate isolated circuits. Instead, it stores energy in its magnetic field and releases that energy back into the circuit as current changes.

Difference in Energy Storage

Energy storage is an important function of an inductor.

In switching power supplies, an inductor can store energy during part of a switching cycle and release it during another part of the cycle.

A conventional power transformer is generally designed primarily for energy transfer rather than storing significant energy in the core.

Some transformer topologies, such as flyback transformers, intentionally store energy as part of their operation, so the exact function depends on the circuit topology.

Voltage Conversion

Transformers are commonly used to change voltage.

A step-up transformer can increase voltage, while a step-down transformer can reduce voltage.

Inductors do not directly convert one voltage level into another in the same way. However, they are essential components in switching converters that regulate and convert DC voltages.

Electrical Isolation

A transformer can provide galvanic isolation between the primary and secondary circuits.

This is one of the major reasons transformers are used in isolated power supplies and safety-related applications.

A conventional single-winding inductor does not provide this type of isolation.

Core Design

Both transformers and inductors can use ferrite, iron powder or other magnetic materials depending on the application.

However, the core design is selected according to the component's function.

Transformer cores are generally designed for efficient magnetic coupling and controlled losses at the operating frequency.

Inductor cores may be designed to store energy and handle a particular DC current without excessive saturation.

Air Gaps

Air gaps are commonly used in many power inductors to increase energy storage capability and control the magnetic behavior of the core.

Some transformers may also use specific gaps depending on their topology and application, but conventional transformers generally aim for efficient magnetic coupling rather than maximizing energy storage.

This is one reason transformer and inductor cores can have different magnetic designs even when they look similar.

Applications

Transformers are commonly found in:

Power supplies
Isolation circuits
Audio equipment
Industrial equipment
EV charging systems
Communication equipment

Inductors are commonly used in:

DC-DC converters
Switching power supplies
EMI filters
Output filters
Automotive electronics
Energy storage systems

Transformer vs Inductor

The basic differences can be understood by looking at their main functions.

A transformer uses multiple windings to transfer energy between circuits and can provide voltage conversion and isolation.

An inductor generally uses one winding to store magnetic energy and control current.

The two components can sometimes look very similar physically, but their core design, winding arrangement and electrical characteristics are optimized for different purposes.

How to Choose Between Them

The circuit function should determine whether you need a transformer or an inductor.

If you need voltage conversion between AC or switching waveforms, electrical isolation or energy transfer between separate windings, a transformer is usually the appropriate component.

If the main requirement is energy storage, current smoothing or filtering, an inductor is generally more suitable.

For switching power supplies, both components may be used in the same design, with the transformer handling energy transfer and isolation while inductors control current and filter the output.

Choosing a Transformer or Inductor Supplier

When sourcing magnetic components, check whether the supplier has experience with the specific component type and application.

For transformers, look at winding structure, insulation, turns ratio, core material and testing capabilities.

For inductors, pay particular attention to inductance, saturation current, DC resistance, core material and temperature rise.

A supplier with custom design and manufacturing capabilities can also be useful when standard components do not meet the requirements of the circuit.