How Is the Pull Force of a Magnet Measured?
The magnet is placed on a thick, flat, ground steel plate and pulled straight up with a force gauge or pull tester. The peak force just before it breaks free is the pull force. Because the test uses ideal steel with no gap, it’s the highest value you’ll see. Real projects hold less.
The Standard Test Setup
- Steel plate: thick enough that it can’t saturate, ground flat and clean.
- No gap: the pole face sits directly on the steel.
- Straight pull: a fixture pulls exactly perpendicular to the plate, with no tilting or peeling.
- Slow, steady loading: force increases gradually until the magnet releases.
- Peak reading: a digital force gauge or load cell records the maximum force.
How Our Listed Ratings Are Set
Depending on the product, the pull force on each listing comes from our own pull testing, from our manufacturer’s test data, or from calculations based on the magnet’s size and grade. All of them describe the same standard setup above, so you can compare one listing to another.
A Check On the Numbers
A magnet acts on thick steel almost exactly like it would on a mirror-image twin magnet. Using that principle, the standard physics model for cylinder magnets predicts how pull force should grow with thickness, and our listed ratings for 1/2 Inch discs follow that curve to within a few percent. See the data in Will stacking magnets make them stronger?
Why You Might Measure Less at Home
| Your setup | Why the reading is lower |
|---|---|
| Thin steel (fridge door, sheet metal) | The steel saturates and can’t carry all the flux |
| Painted or textured surface | Adds an air gap |
| Pulling at an angle | The magnet peels off one edge first |
| Spring or luggage scale | Hard to read the peak and pull perfectly straight |
Magnet Pull Force Calculator
To estimate what your own setup should measure, enter the magnet, your steel thickness and any gap.
Testing a Magnet Yourself
Stick the magnet to the thickest, flattest steel you have, such as a vise jaw or an anvil face, hook a digital luggage scale to it with a non-magnetic loop, and pull straight up slowly. Use the result to compare magnets with each other, not to check against the listed rating.