Antimagnetic
Antimagnetic describes how well a watch resists magnetic fields. Magnetism can make a mechanical watch run fast or stop altogether, and the resistance is rated in gauss or to the ISO 764 standard. A soft-iron inner case or silicon parts add the protection.
At a glance
- Unit of measure
- Gauss or ISO 764
- Protection method
- Soft-iron inner case or silicon parts
- Common magnet sources
- Phones, speakers, laptops
Magnetic fields are invisible, but they go straight to the rate of a mechanical watch: once the steel parts pick up a charge, the watch either runs fast or stops outright. An antimagnetic watch is built to keep that effect out up to a defined threshold.
How the resistance is measured
The strength of the protection is stated two ways, and both say the same thing:
- Gauss: the intensity of the field a watch can take before it drifts
- ISO 764: the standard test a watch has to pass to be called antimagnetic
Below that threshold the watch is unaffected; above it, it can still magnetize. It helps to read this alongside accuracy and deviation, since magnetism shows up directly in the rate.
How it is protected
There are two common methods. The first is a soft-iron inner case around the movement; it draws the magnetic field onto itself and away from the parts that keep time. The second is using non-magnetic components such as silicon, which do not pick up a charge in the first place. Magnets are everywhere in daily life: phones, speakers, and laptops are the three you meet most.
For pieces where this kind of durability stands out, browse the Standards category and our guide to the best Japanese watches.
Examples
Leaving your phone, a speaker, or a laptop next to your watch can make an unprotected mechanical watch run fast or stop.
An antimagnetic watch states its durability through a gauss figure or the ISO 764 test it passes, staying unaffected by fields below that threshold.
Comparison
A soft-iron inner case and silicon parts add protection in different ways.
| Option A | Option B | Notes |
|---|---|---|
| Soft-iron inner case | Silicon parts | The inner case draws the field onto itself and away from the movement; silicon parts simply do not pick up a charge in the first place. |
Related terms
Frequently asked questions
What does a magnetic field do to a watch?
A magnetic field magnetizes the steel parts of a mechanical watch and disturbs its rate, so the watch either runs fast or stops altogether. An antimagnetic watch keeps that out up to a defined threshold and runs unaffected by weaker fields.
How is a watch's antimagnetic resistance measured?
Resistance is stated two ways: in gauss, the strength of the field a watch can take before it drifts, or to the ISO 764 standard. ISO 764 is the test a watch must pass to be called antimagnetic, and both express the same durability.
What can magnetize my watch in daily life?
The most common magnet sources are phones, speakers, and laptops. Leaving your watch right beside them can magnetize a mechanical watch and disturb its rate if it has no antimagnetic protection. A soft-iron inner case or silicon parts reduce that risk.