What Is Inductance? A Simple Guide to µH, mH and H

When selecting an inductor, one of the first parameters you will see is inductance, usually expressed in µH, mH or H.

For customers who are new to inductors, understanding these units is the first step toward choosing the right component.

What Does µH Mean?

The standard unit of inductance is the Henry (H).

However, most inductors used in power supplies, chargers, LED drivers, automotive electronics and other electronic products have much smaller inductance values.

Therefore, the following units are more commonly used:

• 1,000 µH = 1 mH

• 1,000 mH = 1 H

For example:

• 10 µH = 0.01 mH

• 100 µH = 0.1 mH

• 470 µH = 0.47 mH

• 1,000 µH = 1 mH

In customer drawings or specifications, µH is sometimes written as uH or simply “u”.

For example:

22u

22uH

22µH

They normally refer to the same inductance value: 22 microhenries.

Is Inductance Value Enough to Select an Inductor?

No.

A customer may request a 100 µH inductor, but inductance alone is not enough to define the final product.

Other important parameters normally include:

• Rated current

• Saturation current

• DCR

• Core material

• Wire diameter

• Product dimensions

• Operating frequency

• Temperature rise requirement

• Application

For example, two inductors can both be rated at 100 µH, but one may be designed for 0.5 A while another may be designed for several amps.

Their core size, wire diameter and DCR can therefore be completely different.

Why Is This Important?

When sourcing a custom inductor, providing more complete electrical and mechanical parameters allows the manufacturer to recommend a more suitable design.

At our factory, we manufacture custom toroidal inductors according to customer requirements, including inductance, wire diameter, dimensions, current and DCR.

If you are developing a new product and are unsure how to specify your inductor, you can provide your existing sample, drawing or application information for evaluation.