Ferrite Toroid Cores

productsFerrite Cores are available in numerous sizes and several permeabilities (µ). Their permeability range is from 20 to more than 15,000.They are very useful for resonant circuit applications as well as wideband transformers and they are also commonly used for RFI/EMI attenuation. We can supply sizes from 0.23 inches to 2.4 inches outside diameter directly from stock.

Ferrite toroid cores are well suited for a variety of RF circuit applications and their relatively high permeability factors make them especially useful for high inductance values with a minimum number of turns, resulting in smaller component size.

There are two basic ferrite material groups:  (1) Those having a permeability range from 20 to 850 µ  are of the Nickel Zinc (NiZn) class (mix 43,61,67), and (2) those having permeabilities above 850 µ are usually of the Manganese Zinc (MnZn) class (Mix 31,77).

The NiZn ferrite cores exhibit high volume resistivity, moderate temperature stability and high ‘Q’ factors for the 500 KHz to 100 MHz frequency range. They are well suited for low power, high inductance resonant circuits. Their low permeability factors also make them useful for wide band transformer applications.

The MnZn ferrite cores, have permeabilities above 800 µ, have fairly low volume resistivity and moderate saturation flux density. They offer high ‘Q’ factors for the 1 KHz to 1 MHz frequency range. Cores from this group of materials are widely used for switched mode power conversion transformers operating in the 20 KHz to 100 KHz frequency range. These cores are also very useful for the attenuation of unwanted RF noise signals in the frequency range of 2 MHz to 400 MHz and above.

A table of Ferrite core toroids, including physical dimensions and AL  (mH/1000 turns) values, and magnetic properties is found below.

The frequency ranges listed in the table are those recommended for tuned circuits. FOR WIDEBAND TRANSFORMERS THE TOP FREQUENCY IS TEN TIMES HIGHER.

To find the number of turns to give the desired inductance for your coil use the formula below:

              Turns = 1000 x toroid formula


Toroid Core Price Table             

Chart showing mH per 1000 turns.

                             To order specify core size and Mix.  Example: F240-61

                          Available in sizes that have mH per 1000 turns shown in the table.

For F240-31 mix see Ferrite Beads part # FB240-31 2.4″ toroid good for 160-10 meters.

New Product: F400-31 has a 3 inch (76mm) ID for large cables size.  See FB400-31 in Slip On bead page HERE

For Mix Selection Guidelines click here


Ferrite Balun Cores

balun core

Part Number


Width x Thickness

Hole Dia.





.53” x .3”