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Solenoid Magnetic Field Calculator.

Calculate the long-solenoid magnetic field approximation.

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02 / ANSWER

Turns

Current

Solenoid length

Relative permeability

Magnetic field

0.000000T

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Use Cases

Designing electromagnets

Estimate the magnetic field strength for a given solenoid configuration to design electromagnets for experiments or industrial applications.

Example: A solenoid with 500 turns, 0.2 m length, 2 A current, and air core (μ_r=1) gives B ≈ 0.00628 T.

Educational demonstrations

Quickly compute expected fields for classroom demonstrations or lab exercises to verify theoretical predictions.

Example: Check how increasing current or turns affects the field.

Frequently Asked Questions

What is the long-solenoid approximation?: The long-solenoid approximation assumes the solenoid is infinitely long, so the magnetic field inside is uniform and given by B = μ₀ * μ_r * (N/L) * I, where μ₀ is the vacuum permeability, μ_r is the relative permeability, N is the number of turns, L is the length, and I is the current.
How do I use the relative permeability?: Relative permeability (μ_r) is a material property. For air or vacuum, μ_r = 1. For ferromagnetic materials like iron, μ_r can be thousands. Enter the value for the core material to adjust the field strength.
What units should I use?: Enter current in amperes (A), solenoid length in meters (m), and turns as a dimensionless number. The calculator will output the magnetic field in teslas (T).

Tips & Common Mistakes

Tips

Ensure the solenoid length is much greater than its diameter for the long-solenoid approximation to be valid.
Use consistent units: meters for length, amperes for current.
For air-core solenoids, set relative permeability to 1.
Remember that the formula gives the field inside the solenoid, not at the ends.

Common Mistakes to Avoid

Using centimeters for length without converting to meters.
Forgetting to multiply by the relative permeability when using a magnetic core.
Assuming the approximation holds for short solenoids where edge effects are significant.

Last updated: August 13, 2026

Use Cases

Designing electromagnets

Estimate the magnetic field strength for a given solenoid configuration to design electromagnets for experiments or industrial applications.

Example: A solenoid with 500 turns, 0.2 m length, 2 A current, and air core (μ_r=1) gives B ≈ 0.00628 T.

Educational demonstrations

Quickly compute expected fields for classroom demonstrations or lab exercises to verify theoretical predictions.

Example: Check how increasing current or turns affects the field.

Frequently Asked Questions

What is the long-solenoid approximation?

The long-solenoid approximation assumes the solenoid is infinitely long, so the magnetic field inside is uniform and given by B = μ₀ * μ_r * (N/L) * I, where μ₀ is the vacuum permeability, μ_r is the relative permeability, N is the number of turns, L is the length, and I is the current.

How do I use the relative permeability?

Relative permeability (μ_r) is a material property. For air or vacuum, μ_r = 1. For ferromagnetic materials like iron, μ_r can be thousands. Enter the value for the core material to adjust the field strength.

What units should I use?

Enter current in amperes (A), solenoid length in meters (m), and turns as a dimensionless number. The calculator will output the magnetic field in teslas (T).

Tips & Common Mistakes

Tips

Ensure the solenoid length is much greater than its diameter for the long-solenoid approximation to be valid.
Use consistent units: meters for length, amperes for current.
For air-core solenoids, set relative permeability to 1.
Remember that the formula gives the field inside the solenoid, not at the ends.

Common Mistakes to Avoid

Using centimeters for length without converting to meters.
Forgetting to multiply by the relative permeability when using a magnetic core.
Assuming the approximation holds for short solenoids where edge effects are significant.

Use Cases

Designing electromagnets

Estimate the magnetic field strength for a given solenoid configuration to design electromagnets for experiments or industrial applications.

Example: A solenoid with 500 turns, 0.2 m length, 2 A current, and air core (μ_r=1) gives B ≈ 0.00628 T.

Educational demonstrations

Quickly compute expected fields for classroom demonstrations or lab exercises to verify theoretical predictions.

Example: Check how increasing current or turns affects the field.

Frequently Asked Questions

What is the long-solenoid approximation?

How do I use the relative permeability?

What units should I use?

Enter current in amperes (A), solenoid length in meters (m), and turns as a dimensionless number. The calculator will output the magnetic field in teslas (T).

Tips & Common Mistakes

Tips

Ensure the solenoid length is much greater than its diameter for the long-solenoid approximation to be valid.
Use consistent units: meters for length, amperes for current.
For air-core solenoids, set relative permeability to 1.
Remember that the formula gives the field inside the solenoid, not at the ends.

Common Mistakes to Avoid

Using centimeters for length without converting to meters.
Forgetting to multiply by the relative permeability when using a magnetic core.
Assuming the approximation holds for short solenoids where edge effects are significant.