Solenoid Magnetic Field Calculator

About this calculator

A solenoid — a coil of wire wound in tight loops — produces a nearly uniform magnetic field inside its core when current flows through it. That field strength is given by B = μ0·N·I/L, where μ0 is the permeability of free space (4π×10⁻⁷ T·m/A), N is the number of turns, I is the current, and L is the coil's length: more turns or more current packed into a shorter coil means a stronger field.

This relationship is fundamental to designing electromagnets, relays, inductors, MRI magnets, and solenoid valves, and it's a standard formula in introductory electromagnetism courses — this calculator lets you plug in turns, length and current to get the field strength directly instead of working the formula by hand.