Questions and answers on safe distances
Table of Contents
What safety distance should I maintain between magnets and devices?
It is not possible to specify a universal safety distance for magnets. In addition to the magnet's strength, the required distance depends on how sensitive the specific device is to magnetic fields. The following tables show the recommended minimum distances for various magnet sizes and magnet types. Particularly large or strong neodymium magnets must be kept further away from the respective objects than smaller magnets.The following tables show the recommended minimum distances between selected devices and various neodymium or ferrite magnets. The figures are provided as guidelines and apply to the specific magnet versions listed. They may be used as reference for magnets of comparable design, dimensions and magnetic strength.
What are the recommended safe distances for neodymium magnets?
The following table shows the recommended minimum distances for various sizes of neodymium magnets.| Object | Magnetic field damaging at: | S-45-30-N (strength 69 kg) |
S-20-10-N (strength 11 kg) |
S-15-08-N (strength 6,2 kg) |
S-10-03-N (strength 1,8 kg) |
S-06-02-N (strength 740 g) |
|---|---|---|---|---|---|---|
| High-quality magnetic card (credit card, ATM card) | 40 mT (= 400 G) |
46 mm | 19 mm | 15 mm | 9 mm | 6 mm |
| Cheap magnetic card (parking garage, admission ticket) | 3 mT (= 30 G) |
134 mm | 55 mm | 42 mm | 24 mm | 15 mm |
| Pacemaker new | 1 mT (= 10 G) |
201 mm | 82 mm | 62 mm | 35 mm | 22 mm |
| Pacemaker old | 0,5 mT (= 5 G) |
257 mm | 104 mm | 80 mm | 43 mm | 28 mm |
| Mechanical watch, non-magnetic pursuant to ISO 764 | 6 mT (= 60 G) |
103 mm | 42 mm | 32 mm | 18 mm | 12 mm |
| Mechanical watch, not non-magnetic | 0,05 mT (= 0,5 G) |
571 mm | 230 mm | 176 mm | 98 mm | 61 mm |
| Hearing aid | 20 mT (= 200 G) |
63 mm | 26 mm | 20 mm | 12 mm | 7 mm |
| Hard drive | Unclear |
For your convenience, we also summarised all of the information about recommended safe distances for neodymium magnets
in a PDF document:
Download PDF
Download PDF
What are the recommended safe distances for ferrite magnets?
The following table shows the recommended minimum distances for various sizes of ferrite magnets.| Object | Magnetic field damaging at: | FE-S-100-15 (strength 11 kg) |
FE-S-40-20 (strength 4,7 kg) |
FE-S-20-10 (strength 1,4 kg) |
FE-S-05-05 (strength 100 g) |
|---|---|---|---|---|---|
| High-quality magnetic card (credit card, ATM card) | 40 mT (= 400 G) |
21 mm | 20 mm | 18 mm | 3 mm |
| Cheap magnetic card (parking garage, admission ticket) | 3 mT (= 30 G) |
119 mm | 70 mm | 35 mm | 11 mm |
| Pacemaker new | 1 mT (= 10 G) |
182 mm | 106 mm | 53 mm | 16 mm |
| Pacemaker old | 0,5 mT (= 5 G) |
235 mm | 137 mm | 69 mm | 21 mm |
| Mechanical watch, non-magnetic pursuant to ISO 764 | 6 mT (= 60 G) |
89 mm | 53 mm | 27 mm | 8 mm |
| Mechanical watch, not non-magnetic | 0,05 mT (= 0,5 G) |
522 mm | 308 mm | 154 mm | 48 mm |
| Hearing aid | 20 mT (= 200 G) |
45 mm | 30 mm | 15 mm | 5 mm |
| Hard drive | Unclear |
For your convenience, we also summarised all of the information about recommended safe distances for ferrite magnets
in a PDF document:
Download PDF
Download PDF
Which devices and storage media are not affected by magnets?
Many modern, everyday electronic items and non-magnetic storage media are not permanently damaged by static magnetic fields. However, very strong magnets can still cause temporary malfunctions in certain components and sensors. The following examples are trouble-free:- Chip on a bank card: Ordinary household magnets do not damage the chip.
- Camera, smartphone, tablet: Stored data is not erased; however, strong magnets can temporarily affect sensors or mechanical components.
- Vehicle key: The transponder is not damaged by a static magnetic field.
- USB stick, memory cards: Static magnetic fields do not erase data.
- CD, DVD: Magnets do not erase data.
- RFID chip: A magnet cannot erase the stored data.
Which devices are particularly sensitive to magnets?
Pacemakers, implanted defibrillators, hearing aids and neurostimulators can be affected by strong magnetic fields. Magnets can cause temporary malfunctions in these devices or activate a specific operating mode. Therefore, always follow the recommended safe distance for the device in question. You can obtain information on the recommended safe distances from the device manufacturer or your attending physician.Frequently asked questions about magnets and electronic devices
Can a magnet damage my smartphone?
No, magnets do not erase data on modern smartphones.
Current smartphones use non-magnetic storage media and are not damaged by the magnetic field of a permanent magnet.
However, magnetic fields can magnetise, and potentially damage, sensors, mechanical parts or the built-in speakers of these devices. Therefore, when in doubt, keep strong magnets away from such devices. This applies not only to smartphones but also to digital cameras, tablets and other small electronic devices.
Can a magnet erase data from a mobile phone?
No, magnets cannot erase the data stored on a modern smartphone.Can a magnet damage smartwatches or smart rings?
No, magnets do not usually damage smartwatches or smart rings. However, strong magnetic fields can temporarily interfere with their sensors and functions.Can a magnet damage a hard drive?
Yes, strong magnets can damage magnetic hard disk drives (HDDs) or corrupt stored data. However, the risk depends heavily on the design of the hard drive and the distance from the magnet.Hard drives installed in desktop PCs are generally well protected. As they are housed within the case, it is nearly impossible to bring a magnet close enough to the hard drive to cause damage. External hard drives, as well as older models or HDDs built into laptops, are more vulnerable, as they are often situated closer to the surface of the casing.
Since hard drives vary by manufacturer and design, we cannot specify universally applicable safe distances. As a general guideline: at a distance of approximately 20 cm, even our strongest magnet should not damage a hard drive.
Can a magnet erase data from my hard drive?
You cannot reliably erase data from a hard drive using a magnet. Whilst strong magnets can damage data on magnetic hard drives, they are not suitable for deliberately and completely wiping a hard drive. If you want to permanently delete data from a hard drive, permanent magnets are not a reliable solution. Instead, use specialised data-wiping programmes that completely overwrite the hard drive multiple times.Modern solid-state drives (SSDs), which do not contain a magnetic coil, cannot be damaged or erased by a magnet. They do not have magnetic platters that could be affected by magnetic fields. If the data storage device is to be disposed of permanently, a professional physical destruction is recommended.
Can magnets damage USB sticks and memory cards?
No, USB flash drives and memory cards (CompactFlash, SecureDigital, etc.) are not magnetic data storage devices. Therefore, they are not damaged when exposed to static magnetic fields.Can magnets damage CDs and DVDs?
No. CDs and DVDs are not magnetic data storage devices and are therefore not damaged when exposed to static magnetic fields.Can magnets erase RFID chips?
No. The data on an RFID tag is transmitted using a radio signal and is not stored magnetically on the tag. Information on RFID chips cannot be erased with magnets.Can magnets damage vehicle keys?
No, a static magnetic field does not damage a vehicle key or the built-in transponder for the anti-theft device. You can hang your car key on a magnetic key rack without hesitation.Frequently asked questions about magnets and medical devices
Can magnets affect pacemakers and defibrillators?
Yes, strong magnets can temporarily switch pacemakers and implanted defibrillators into a special mode. Once the magnet is removed, the devices usually return to normal operating mode.Sensitivity to magnetic fields varies depending on the device and manufacturer. You should therefore follow the safe distances given in the table, as well as the specific instructions provided by the device manufacturer and your attending physician.
Can magnets affect cardiac stents?
No, cardiac stents are generally not affected by magnets. However, the situation is different for electronic implants such as pacemakers or defibrillators. In these cases, you must follow the recommended safe distances from magnets.Can magnets affect neurostimulators?
Yes, magnets can interfere with the functioning of implanted neurostimulators. Therefore, it is essential to observe the safe distance from magnets as recommended by your implant manufacturer.Can magnets interfere with hearing aids?
Yes, magnetic fields can impair the functioning of hearing aids. For example, they may cause disruption to the acoustic signal or wireless communication. You should therefore follow the safe distances to magnets as recommended by your hearing aid manufacturer.Frequently asked questions about magnets and everyday objects
Are the magnetic stripes on bank cards / magnetic cards sensitive to magnets?
Nowadays, bank and credit cards mostly feature high-quality magnetic stripes. These dark brown to black stripes are relatively resistant to magnetic fields. Magnetic accessories, such as mobile phone accessories, are generally not strong enough to damage them. However, direct contact with strong magnets can erase the data on the magnetic stripe, as our experiment with magnets and credit cards showed. You can find the related information in the video Magnets vs Credit Card.The magnetic stripe is of little relevance today for payments and cash withdrawals within Europe, as the chip is used for these purposes. Furthermore, Mastercard plans to completely remove magnetic stripes from its cards starting in 2033.
Cheaper magnetic stripes, such as those found on car park or trade fair tickets, are more sensitive than the magnetic stripes on bank and credit cards. Even relatively weak magnetic fields can corrupt or erase the stored data.
EMV chips on bank cards cannot be damaged by standard household magnets. Nevertheless, it is advisable to avoid exposing bank cards to strong magnets unnecessarily.
Can magnets damage a mechanical watch?
Yes, strong magnetic fields can magnetise components of a mechanical watch, such as the balance spring. This can cause the watch to run fast or slow.Many commercially available watches are classified as antimagnetic under ISO 764 and must withstand a magnetic field of 6 mT; specially designed models can often withstand significantly stronger fields.
For non-antimagnetic watches, it is not possible to specify a general safe distance.
So, as a precaution, keep them away from strong magnetic fields.
A watchmaker can demagnetise a magnetised mechanical watch using a demagnetiser.
Analogue quartz watches kmay temporarily run faster or slower, or stop altogether, when exposed to strong magnetic fields. Once the magnet is removed and the time is corrected, they should function normally again.
