Ampere-Turn Calculator

Calculate the magnetic field strength of a coil with the Ampere-Turn Calculator, and learn how 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

Enter the Applied Current and the Number Of Turns

How To Calculate Ampere-Turns

Enter some values to get started!

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

How To Calculate Ampere-Turns: This feature displays a live example of how to calculate ampere-turns or Gilberts using the figures that you enter

The result is calculated and updated automatically as you enter different numbers or change between the input fields. If the calculated result hasn’t updated after you’ve finished entering your values, click or tap on the result.

Reference: ARRL – The Radio Amateur’s Handbook