Calculator inputs
Enter the cylinder coil dimensions, current, material effect, and the axial position where you want the magnetic field evaluated.
Formula used
This calculator models the cylinder as a finite cylindrical coil and evaluates the magnetic field on its central axis.
- B(z) = magnetic flux density at axial position z
- μ0 = permeability of free space
- μr = relative permeability of the core region
- N = total turns
- L = cylinder length
- R = cylinder radius
- I = current through the winding
The model is most useful for on-axis estimates. Off-axis fields and permanent magnet cylinders require different equations.
How to use this calculator
- Enter the cylinder radius and total coil length.
- Enter the total number of turns wound around the cylinder.
- Enter current and choose its unit.
- Set the relative permeability for the medium or core.
- Enter the axial position measured from the cylinder center.
- Select your preferred output field unit.
- Choose graph span and point count for the plotted field profile.
- Press calculate to show the result above the form.
- Use the CSV or PDF buttons to export your results.
Example data table
| Case | Radius | Length | Turns | Current | μr | z | Approx. field |
|---|---|---|---|---|---|---|---|
| Air-core center check | 3 cm | 12 cm | 800 | 2.5 A | 1 | 0 cm | 18.733 mT |
| Offset point check | 4 cm | 18 cm | 1200 | 3 A | 1 | 5 cm | 20.969 mT |
| Higher core effect | 2.5 cm | 10 cm | 1500 | 1.2 A | 5 | 0 cm | 101.157 mT |
| Longer cylinder | 5 cm | 25 cm | 900 | 4 A | 1 | 10 cm | 12.879 mT |
Frequently asked questions
1. What does this calculator estimate?
It estimates the magnetic field on the axis of a finite cylindrical coil. It reports the field at your chosen point, the center, and the edge.
2. Is this for a permanent magnet cylinder?
No. This page uses a current-carrying cylindrical coil model. A solid permanent magnet cylinder needs a different magnetic model and different material data.
3. Why does the field change with position?
The coil is finite, so each point along the axis sees a different contribution from the winding. The field is usually strongest near the center.
4. What is relative permeability?
Relative permeability describes how strongly a material supports magnetic flux compared with free space. Larger values can increase the estimated flux density.
5. What units can I use?
You can enter lengths in meters, centimeters, millimeters, or inches. Current accepts amperes, milliamperes, or kiloamperes. Results can display in tesla, millitesla, microtesla, or gauss.
6. What is the difference between B and H?
B is magnetic flux density. H is magnetic field strength. They are related through permeability, so both values help describe the magnetic behavior.
7. Why include graph span and graph points?
Graph span controls how far the plotted axis extends. Graph points control curve smoothness. More points create a denser chart and export dataset.
8. When should I use a different method?
Use a different method for off-axis fields, permanent magnets, fringe-sensitive engineering design, or cases needing full finite element analysis and material saturation effects.