Estimate magnet force using practical models and flexible inputs. See graphs, conversions, and assumptions instantly. Export tables and reports for labs, classes, projects, reviews.
| Case | Method | Magnet 1 | Magnet 2 | Distance | Approx. Force |
|---|---|---|---|---|---|
| Lab Sample A | Pole strength | 0.80 A·m | 0.70 A·m | 3.0 cm | 0.000062 N |
| Lab Sample B | Pole strength | 1.50 A·m | 1.20 A·m | 5.0 cm | 0.000072 N |
| Axial Pair C | Dipole approximation | 0.40 A·m² | 0.35 A·m² | 4.0 cm | 0.032813 N |
| Axial Pair D | Dipole approximation | 0.25 A·m² | 0.18 A·m² | 6.0 cm | 0.002083 N |
Use this when a simplified pole model fits the problem. The force magnitude is estimated by F = (μ₀ / 4π) × (p₁ × p₂) / r².
Here, μ₀ is the permeability of free space, p₁ and p₂ are pole strengths, and r is separation distance.
Use this when magnets behave like small axial dipoles. The force magnitude is estimated by F = k × (3μ₀m₁m₂) / (2πr⁴).
Here, m₁ and m₂ are dipole moments, r is separation distance, and k is the alignment factor for practical adjustment.
These equations are approximations. Real magnets depend on geometry, material grade, edge effects, temperature, and orientation. Very short gaps can differ strongly from the simplified models.
Magnetic force is highly sensitive to distance. Even a small gap change can cause a large force change. That is why engineers and students often begin with compact formulas before moving to finite element tools or measured test data. A quick estimate is useful for lab setups, holding fixtures, educational demonstrations, sensor layouts, and low-risk design checks.
The pole strength model is easy to understand and gives a useful inverse-square relationship. It is often used for conceptual problems and rough comparisons. The dipole model is more common when magnets are treated as magnetic moments. It creates a much stronger distance sensitivity because the force changes with the fourth power of distance in the axial approximation. This makes it helpful when studying how force falls off as magnets move apart.
Real magnets are not perfect points or ideal dipoles. Shape, magnet grade, steel parts nearby, shielding, temperature, and tilt angle can all change the outcome. Surface-to-surface force can be much larger than the simple estimate suggests, while off-axis alignment can reduce force quickly. For accurate product design, measured pull-force curves or simulation data remain the best reference.
This calculator includes charting plus CSV and PDF export so you can keep a record of assumptions, compare several distances, and share quick findings with classmates, clients, or project teammates.
Use pole strength for simple conceptual estimates. Use dipole approximation when magnetic moments are known and axial behavior is a reasonable assumption.
Magnetic interactions weaken rapidly as separation grows. In these models, force changes with either inverse-square or inverse-fourth distance behavior.
It scales the dipole estimate for practical orientation differences. A value of 1 represents the base axial estimate in this page.
Only as a rough estimate. Very short gaps often need measured data or detailed simulation because fringe effects become important.
The sign helps indicate direction. Attractive interaction is often treated as negative, while repulsive interaction is treated as positive.
You can enter distance in meters, centimeters, millimeters, inches, or feet. Magnitude and area units are also selectable.
It divides force by the effective area you enter. This provides a simple force-per-area estimate, not a full contact mechanics solution.
It is best for early checks, learning, and comparison. Final approval should rely on validated testing, vendor data, or advanced simulation.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.