If one magnet does not provide enough pull force, will stacking two magnets together make them twice as strong?

The short answer is:

Stacking magnets usually increases the overall magnetic performance, but the pull force does not increase in direct proportion to the number of magnets.

For relatively thin magnets, increasing thickness can significantly improve pull force. However, as more magnets are added, the benefit of each additional magnet becomes smaller.

This is known as diminishing returns.

1. Why Does Stacking Magnets Make Them Stronger?

Take two axially magnetized disc magnets with the same size, grade, and magnetization direction.

If they are stacked with the correct N/S pole orientation, they can behave approximately like one thicker magnet.

For example:

• 1 magnet: D20 × 5 mm

• 2 stacked magnets: approximately D20 × 10 mm

• 3 stacked magnets: approximately D20 × 15 mm

Increasing the magnet length in the magnetization direction usually strengthens the external magnetic field and improves pull force.

However, this does not mean:

2 magnets = 2× the pull force

or

3 magnets = 3× the pull force

2. Why Doesn't Pull Force Keep Increasing Proportionally?

The key reason is that each additional magnet is farther away from the working surface.

The first magnet is closest to the steel plate and contributes the most to the pull force.

Adding a second magnet can produce a noticeable improvement.

But when a third or fourth magnet is added, those magnets are farther from the steel surface, so their contribution becomes progressively smaller.

Data published by K&J Magnetics for disc magnets of the same diameter shows this clearly:

When a thin magnet becomes thicker, the increase in pull force can be significant.

But once the magnet is already relatively thick, adding more magnetic material may produce only a small improvement.

So:

More stacked magnets do not always mean proportionally more strength.

3. Magnetic Field Strength and Pull Force Are Not the Same

When discussing whether a magnet is "stronger," it is important to distinguish between two different concepts.

Surface Magnetic Field

This is usually measured in Gauss or Tesla and describes the magnetic flux density at a specific point near the magnet.

Pull Force

This refers to the force required to separate a magnet from a steel surface.

Pull force is also affected by:

• magnet size

• contact area

• steel thickness

• steel grade

• surface condition

• working air gap

Therefore, a higher Gauss reading does not necessarily mean the pull force will increase by the same percentage.

4. When Is Stacking Magnets Most Effective?

Stacking is usually more effective when the original magnet is relatively thin.

For example:

D20 × 2 mm
increased to
D20 × 4 mm

may produce a noticeable improvement.

But if the magnet is already:

D20 × 20 mm

increasing it to:

D20 × 40 mm

may provide only a limited gain.

A useful engineering rule of thumb is:

As the magnet length in the magnetization direction approaches its lateral dimension, further increases in thickness tend to produce stronger diminishing returns.

This is not a strict design rule, but it can be useful during early-stage magnet selection.

5. If Pull Force Is Too Low, Should You Stack Magnets or Use a Larger Magnet?

If the current magnet does not provide enough force, there are several possible solutions.

Option 1: Stack Magnets

This is suitable for:

• prototype testing

• product development

• small-volume projects

• quick performance verification

The main advantage is flexibility. You can test the effect of greater magnetic thickness without immediately changing the magnet specification.

Option 2: Use One Thicker Magnet

If testing confirms that greater thickness is needed, you may consider replacing:

2 × D20 × 5 mm

with:

1 × D20 × 10 mm

A one-piece magnet can reduce assembly steps, tolerance stack-up, and the risk of magnets colliding during installation.

Option 3: Increase Diameter or Working Area

If the magnet is already relatively thick, continuing to increase thickness may not be efficient.

In this case, increasing the:

diameter, width, or effective pole area

may sometimes provide a better result.

6. Can a Higher Magnet Grade Replace Stacking?

Not always.

For example, if an N35 magnet does not provide enough pull force, possible solutions include:

• increasing thickness

• increasing diameter

• changing to N42, N48, or N52

• optimizing the steel component or magnetic circuit

Which option works best depends on the actual design.

If the magnetic circuit is already limited by steel saturation, air gap, or contact area, simply changing to a higher magnet grade may not produce the expected improvement.

For engineering selection, it is better to evaluate:

size + grade + magnetic circuit + working air gap

rather than focusing only on the magnet grade.

7. Why Is Actual Pull Force Often Lower Than the Rated Value?

The pull force listed by a magnet supplier is usually measured under relatively ideal test conditions.

In a real application, pull force can be reduced by:

• paint

• coatings

• plastic layers

• adhesive

• air gaps

• uneven surfaces

If the steel plate is too thin, it may also limit magnetic flux and reduce the benefit of stacking more magnets.

For critical industrial applications, a better approach is:

magnetic circuit evaluation + sample testing + safety factor

8. FAQ

Do two stacked magnets become stronger?

Usually, yes.

When stacked with the correct pole orientation, two magnets can behave approximately like one thicker magnet.

However, the pull force usually does not double.

Will three magnets have three times the pull force?

Usually not.

As more magnets are added, the contribution of each additional magnet becomes smaller.

Are two thin magnets the same as one thick magnet?

In a simple magnetic circuit, their performance may be similar.

However, actual results can be affected by coating layers, assembly gaps, accumulated tolerances, and fixing methods.

Why does adding another magnet sometimes make little difference?

Possible reasons include:

• the original magnet is already relatively thick

• the steel plate is too thin

• there is a large air gap

• the steel is close to magnetic saturation

• the pole orientation is incorrect

• the overall magnetic circuit is limiting performance

Conclusion

Stacking magnets usually increases magnetic performance, but the improvement is not unlimited.

For thin magnets, increasing thickness can be very effective. But as the magnet becomes thicker, each additional magnet usually provides a smaller improvement.

Therefore, if your current magnet does not provide enough pull force, do not only consider adding another magnet.

You should also evaluate:

magnet thickness, diameter, grade, working air gap, and magnetic circuit design.

For prototype testing and early product development, stacking magnets is a simple and useful way to verify performance.

For long-term mass production, however, redesigning the application around a properly sized one-piece custom magnet may offer better results in terms of cost, assembly, and consistency.