Magnetic Field Calculator (B)
Choose a geometry, enter values, and calculate magnetic field strength in tesla (T), millitesla (mT), and microtesla (µT).
What this magnetic field calculator does
This tool estimates magnetic flux density (B) for three common textbook cases: a long straight conductor, a circular current loop, and a long solenoid. It is useful for students, hobbyists, and engineers who want quick values without manually rearranging equations.
- Wire: field at distance r from a current-carrying wire.
- Loop: field at the center of a loop with N turns.
- Solenoid: field inside an ideal long coil.
Core formulas used
1) Long straight wire
B = μ₀I / (2πr)
Where I is current in amperes and r is the radial distance in meters. Field strength decreases as distance increases.
2) Circular loop (center point)
B = μ₀NI / (2R)
Here, R is loop radius and N is number of turns. Increasing turns or current increases field strength.
3) Long solenoid
B = μ₀(N/L)I
This assumes an ideal, sufficiently long solenoid with mostly uniform field inside. The term N/L is turns per meter.
How to use the calculator
- Select the geometry that matches your setup.
- Enter current and dimensions in SI units (A and m).
- Click Calculate Magnetic Field.
- Read result in T, mT, and µT.
Unit quick guide
- 1 tesla (T) = 1,000 millitesla (mT)
- 1 tesla (T) = 1,000,000 microtesla (µT)
- Earth's magnetic field is typically around 25–65 µT depending on location.
Practical notes and limitations
These equations are idealized. Real systems can differ because of finite wire length, coil edge effects, nearby magnetic materials, current ripple, and geometry imperfections. For precision design, verify with measurement or electromagnetic simulation.
Safety reminder
Strong magnetic fields can affect electronics, magnetic media, medical implants, and sensors. Keep proper spacing and follow lab safety protocols.
FAQ
Why are my values very small?
Magnetic fields from low current and larger distances are often tiny in tesla. Use mT or µT for easier interpretation.
Does this include core materials (iron/ferrite)?
No. The current calculator assumes free space (vacuum permeability μ₀). Magnetic cores can increase flux density significantly.
Can I use centimeters instead of meters?
Convert to meters first for correct results. For example, 5 cm = 0.05 m.