Calculating adhesive force magnetic tape/magnetic sheet

The adhesive force of magnetic tapes, magnetic adhesive tapes and magnetic sheets depends not only on the product itself, but also on the direction of the load. Please note: The specifications in g/cm² listed in our shop were measured under ideal conditions. For practical applications, please take the relevant parameters into account.

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What is the difference between adhesive force and holding strength?

Adhesive force comes into play when the magnet is positioned parallel to the contact surface. Holding strength describes the maximum load that can be applied without the magnetic tape slipping or detaching. You can find more information on adhesive force in our FAQ on adhesive force vs. displacement force.

Does the same load direction apply to ferrite tape and neodymium tape?

Not necessarily. Ferrite tape and neodymium tape should be considered separately, as their directions of magnetisation may differ. Please always pay attention to the following directions of magnetisation:

How does the load direction affect the adhesive force in ferrite magnetic tapes

Illustration – Direction of force when two magnetic tapes are placed on top of each other

Explanation of the load direction using ferrite tapes as an example
a = Magnetic adhesive force
b = Holding strength perpendicular to the magnetisation stripes
c = Holding strength parallel to the magnetisation stripes

Magnetic adhesive force (a): At a right angle to the surface the needed strength for separating the magnetic tape from the steel plate is measured. Our adhesive force indications in our shop always refer to stress from this direction. However, the adhesive force of two tapes together is up to 50% higher compared to tape and iron because the tape is an ideal adhesive surface.
Holding strength perpendicular (b): This type of stress happens when you hang an object (e.g. a picture or a sign) with a horizontal magnetic tape onto another horizontal magnetic tape on the wall. If the load becomes too heavy, the tape will eventually "jump" to the next-but-one stripe or be pushed off the other tape, causing the object to fall to the floor. This happens at a load of about 80% of the magnetic adhesive force.
Holding strength parallel (c): The friction of plastic on plastic is not very high. Hence, the adhesive force in this direction is only about 40% of the specifications in our shop.

What is the adhesive force of ferrite magnetic tape?

The following values show typical adhesive force and holding strength for our Magnetic adhesive tape ferrite 30 mm

	Magnetic tape on iron	Magnetic tape on magnetic tape
Magnetic adhesive force (a)	102 g/cm² (100%)	153 g/cm² (150%)
Holding strength diagonal (b)	25 g/cm² (25%)	81 g/cm² (80%)
Holding strength parallel (c)	25 g/cm² (25%)	41 g/cm² (40%)

How does the load direction affect the adhesive force in neodymium magnetic tapes and magnetic sheet?

Explanation of the load direction using neodymium tapes as an example
a = Magnetic adhesive force
b = Holding strength perpendicular to the magnetisation stripes
c = Holding strength parallel to the magnetisation stripes

Magnetic adhesive force (a): At a right angle to the surface the needed strength for separating the magnetic tape from the steel plate is measured. Our adhesive force indications in our shop always refer to stress from this direction. However, the adhesive force of two tapes together is up to 50% higher compared to tape and iron because the tape is an ideal adhesive surface.
Holding strength perpendicular (b): This type of stress happens when you hang an object (e.g. a picture or a sign) with a vertical magnetic tape onto another vertical magnetic tape on the wall. If the load becomes too heavy, the tape will eventually "jump" to the next-but-one stripe or be pushed off the other tape, causing the object to fall to the floor. This happens at a load of about 80% of the magnetic adhesive force.
Holding strength parallel (c): The friction of plastic on plastic is not very high. Hence, the adhesive force in this direction is only about 40% of the specifications in our shop.

What is the adhesive force of neodymium magnetic tape?

The following values show typical adhesive force and holding strength for our Magnetic adhesive tape neodymium 30 mm

	Magnetic sheet on iron	Magnetic sheet on magnetic sheet
Magnetic adhesive force (a)	450 g/cm² (100%)	675 g/cm² (150%)
Holding strength diagonal (b)	112 g/cm² (25%)	360 g/cm² (80%)
Holding strength parallel (c)	112 g/cm² (25%)	180 g/cm² (40%)

What is the adhesive force of neodymium magnetic sheet?

The following values show typical adhesive force and holding strength for our self-adhesive magnetic sheet MS-A4-STIC

	Magnetic sheet on iron	Magnetic sheet on magnetic sheet
Magnetic adhesive force (a)	80 g/cm² (100%)	120 g/cm² (150%)
Holding strength diagonal (b)	20 g/cm² (25%)	64 g/cm² (80%)
Holding strength parallel (c)	20 g/cm² (25%)	32 g/cm² (40%)

How do I calculate the permissible weight for my application?

To calculate the correct weight for your application, it is not just the adhesive force that matters. The specific application situation must also be taken into account. It is particularly important to determine whether the magnetic tape will be subjected to a vertical load or whether the tape is likely to slip sideways. The following examples show calculations for typical applications.

A numeric example with maximum adhesive force (Case a)

For rectangular products calculate the area (length x width in cm) and multiply it with our adhesive force specification.

E.g. Magnetic adhesive tape ferrite 30 mm with 102 g/cm²

At a length of 1 metre: 100 cm x 3 cm = 300 cm² x 102 g/cm² = 30 600 g
At a length of 2 metres: 200 cm x 3 cm = 600 cm² x 102 g/cm² = 61 200 g
At a length of 5 metres: 500 cm x 3 cm = 1 500 cm² x 102 g/cm² = 153 000 g

E.g. Magnetic adhesive tape neodymium 30 mm with 450 g/cm² at a length of 1 metre: 100 cm x 3 cm = 300 cm² x 450 g/cm² = 135 000 g = 135 kg

For round products calculate the area (Pi x radius² in cm) and multiply it with our adhesive force specification.

E.g. Self-adhesive magnetic sheet MS-A4-STIC with 80 g/cm²

For a sphere with a radius of 5 cm: 3,14 x 25 cm² = 78 cm² x 80 g/cm² = 6 240 g
For a sphere with a radius of 10 cm: 3,14 x 100 cm² = 314 cm² x 80 g/cm² = 25 120 g

A numeric example with holding strength diagonal (Case b)

Reverse side of an aluminium sign with a piece of magnetic tape (attached horizontally)

Task: A piece of Magnetic adhesive tape ferrite 30 mm, 30 mm wide and 300 mm long, is glued horizontally to the backside of an aluminium sign. Another magnetic tape of the same size is glued horizontally to a non-magnetic door. How heavy can the sign be to adhere securely to the door?

Calculation: The magnetic strip has an area of 20 cm x 3 cm = 60 cm². The tape has a maximum adhesive force of 102 g/cm² (according to specifications in the web shop). Therefore, the maximum adhesive force of the entire strip is 60 x 102 = 6 120 g, ergo approx. 6 kg.

For the planned vertical strain between the two tapes, you can expect at the most 80% holding strength, ergo max. approx. 4,8 kg.

You should always allow for a generous safety margin. In this case it would be good if the sign didn't weigh more than 3 kg, because the door is exposed to strong vibrations when it is being slammed shut.

Reverse side of an aluminium sign with two pieces of magnetic tape (attached horizontally)

If the sign is heavier, we recommend using a second or third strip of magnetic tape or a very wide magnetic tape such as Magnetic adhesive tape ferrite 150 mm, for instance. Strongly magnetised magnetic tape, Magnetic adhesive tape neodymium 30 mm, is also suitable for attaching heavy signs. In extreme cases, you can use a self-adhesive magnetic sheet MS-A4-STIC and glue it over the whole backside of the sign. That's what we did with a kitchen timer in the following video.

A numeric example with holding strength parallel (Case c)

Reverse side of an aluminium sign with a piece of magnetic tape (attached vertically)

Task: Identical to Case b, but here we glue the magnetic tape vertically and centred on the backside of a sign. Instead of 20 cm the tape is only 15 cm long.

Calculation: The maximum adhesive force of the tape is 30 x 102 = 3060 g, ergo approx. 3 kg. For the planned parellel strain between the two tapes you can expect at the most 40% holding strength, ergo max. approx. 1,2 kg.

This is probably not sufficient to attach the sign securely to the door, because it swings open and shut and is exposed to vibrations. The parallel strain of a magnetic tape is therefore not recommended. If you can't avoid it, use several vertical strips of magnetic tape to increase the holding strength or the extremely magnetised tape Magnetic adhesive tape neodymium 20 mm. Or as mentioned above, you can use a self-adhesive magnetic sheet MS-A4-STIC and glue it on the entire backside of the sign.

Which factors influence the actual adhesive force?

The adhesive force specifications in the web shop require ideal conditions. Material, surface texture and working temperature have a significant influence on the adhesive force of a magnetic tape or magnetic sheet.

The maximum adhesive force can only be achieved on smooth surfaces and on full contact. The tape or sheet needs to be placed flat and directly on the counterpart and must not produce bubbles.
Magnetic tapes and magnetic sheets cannot achieve the adhesive force of neodymium magnets.
If there is no direct contact with an iron counterpart, the adhesive force decreases. A piece of paper between tape or sheet and the mounting surface is already enough to reduce the adhesive force.
Magnetic tapes and sheets do not adhere to magnetic glass boards because the distance is too great.

You can find more information regarding general adhesive force in the FAQ on adhesive force factors.
Please note: Before applying magnetic tape and sheet to large areas, we recommend experimenting with a smaller order first.