Ampere-Turn Calculator

Calculate the magnetic field strength of a coil with the Ampere-Turn Calculator and learn on the go with the integrated live example

The SI unit for the magnetic field strength or magnetomotive force (M.M.F.) of a coil or electromagnet is called the Ampere-Turn or Amp-Turn.

The formula for calculating the magnetomotive force is:


M.M.F. = Magnetomotive force in Ampere-Turns
N = Number of turns
I = Current in amperes (A)

The cgs unit of magnetomotive force is the Gilbert. The formula is:


M.M.F. = Magnetomotive force in Gilberts
N = Number of turns
I = Current in amperes (A)

The formula to convert Ampere-Turns to Gilberts is:

1\; Gilbert=\frac{10}{4\pi}=0.79577\; Ampere-Turn

Increasing the number of turns in a coil while keeping the current the same increases the magnetic field strength.

Example 1: The M.M.F. of a 50 turn coil with 4 amperes through it is:

M.M.F.= 50\times 4=200\; Ampere-Turn

Example 2: The M.M.F. of a 75 turn coil with 4 amperes through it is:

M.M.F.= 75\times 4=300\; Ampere-Turn

Using the Ampere-Turn Calculator

Applied Current: Input the current that will be applied to the coil

Number Of Turns: Enter the total number of turns

Selecting units: You can choose your preferred units of measurement through selecting the units cells and clicking the downwards pointing arrow to display a list of available options

Learn As You Go: This feature displays a live example of how to calculate ampere-turns or Gilberts using the figures that you enter

Enter the Applied Current and the Number Of Turns

How To Calculate Ampere-Turns

Enter some values to get started!

Reference: ARRL – The Radio Amateur’s Handbook