Physics

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Magnetic Field of a Straight Wire Calculator.

Calculate the field magnitude around an ideal infinite straight current-carrying wire.

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02 / ANSWER

Current

Perpendicular distance

Magnetic field

0.000000T

Results update automatically as you type.

Use Cases

Physics homework and exam prep

Quickly verify magnetic field calculations for textbook problems involving long straight conductors, saving time and reducing errors.

Example: Find the field 0.05 m from a wire carrying 10 A.

Engineering design checks

Estimate magnetic field strength near power lines or busbars to assess potential interference or safety considerations.

Example: Check the field at a distance of 1 m from a 100 A industrial line.

Frequently Asked Questions

What does this calculator do?: It calculates the magnitude of the magnetic field produced by an ideal infinite straight wire carrying a steady current. You input the current in amperes and the perpendicular distance from the wire in meters, and it returns the field strength in teslas.
What formula does it use?: It uses the Biot-Savart law for an infinite straight wire: B = (μ₀ * I) / (2π * r), where μ₀ is the permeability of free space (4π × 10⁻⁷ T·m/A), I is the current in amperes, and r is the perpendicular distance in meters.
Is this calculator valid for finite wires?: No, it assumes an ideal infinite straight wire. For finite wires, the field is weaker and depends on the wire's length and the position relative to its ends. This calculator is best for long wires where end effects are negligible.

Tips & Common Mistakes

Tips

Ensure the distance is measured perpendicular to the wire, not along a slanted line.
Use consistent units: current in amperes and distance in meters to get the field in teslas.
For long but finite wires, this calculator gives a good approximation if the distance is much smaller than the wire's length.
Remember that the field direction is circular around the wire, but this calculator only gives magnitude.

Common Mistakes to Avoid

Using the distance from the wire's end instead of the perpendicular distance to the wire.
Forgetting to convert units (e.g., using centimeters without converting to meters).
Assuming the formula applies to short wires or points near the ends of a finite wire.

Last updated: August 13, 2026

Use Cases

Physics homework and exam prep

Quickly verify magnetic field calculations for textbook problems involving long straight conductors, saving time and reducing errors.

Example: Find the field 0.05 m from a wire carrying 10 A.

Engineering design checks

Estimate magnetic field strength near power lines or busbars to assess potential interference or safety considerations.

Example: Check the field at a distance of 1 m from a 100 A industrial line.

Frequently Asked Questions

What does this calculator do?

It calculates the magnitude of the magnetic field produced by an ideal infinite straight wire carrying a steady current. You input the current in amperes and the perpendicular distance from the wire in meters, and it returns the field strength in teslas.

What formula does it use?

It uses the Biot-Savart law for an infinite straight wire: B = (μ₀ * I) / (2π * r), where μ₀ is the permeability of free space (4π × 10⁻⁷ T·m/A), I is the current in amperes, and r is the perpendicular distance in meters.

Is this calculator valid for finite wires?

No, it assumes an ideal infinite straight wire. For finite wires, the field is weaker and depends on the wire's length and the position relative to its ends. This calculator is best for long wires where end effects are negligible.

Tips & Common Mistakes

Tips

Ensure the distance is measured perpendicular to the wire, not along a slanted line.
Use consistent units: current in amperes and distance in meters to get the field in teslas.
For long but finite wires, this calculator gives a good approximation if the distance is much smaller than the wire's length.
Remember that the field direction is circular around the wire, but this calculator only gives magnitude.

Common Mistakes to Avoid

Using the distance from the wire's end instead of the perpendicular distance to the wire.
Forgetting to convert units (e.g., using centimeters without converting to meters).
Assuming the formula applies to short wires or points near the ends of a finite wire.

Use Cases

Physics homework and exam prep

Quickly verify magnetic field calculations for textbook problems involving long straight conductors, saving time and reducing errors.

Example: Find the field 0.05 m from a wire carrying 10 A.

Engineering design checks

Estimate magnetic field strength near power lines or busbars to assess potential interference or safety considerations.

Example: Check the field at a distance of 1 m from a 100 A industrial line.

Frequently Asked Questions

What does this calculator do?

What formula does it use?

Is this calculator valid for finite wires?

Tips & Common Mistakes

Tips

Ensure the distance is measured perpendicular to the wire, not along a slanted line.
Use consistent units: current in amperes and distance in meters to get the field in teslas.
For long but finite wires, this calculator gives a good approximation if the distance is much smaller than the wire's length.
Remember that the field direction is circular around the wire, but this calculator only gives magnitude.

Common Mistakes to Avoid

Using the distance from the wire's end instead of the perpendicular distance to the wire.
Forgetting to convert units (e.g., using centimeters without converting to meters).
Assuming the formula applies to short wires or points near the ends of a finite wire.