About the Inductor Calculator
An inductor stores energy in a magnetic field, and its size is measured in henries. When you join several inductors you get a new total, and the sum depends on how they are wired. This calculator takes a list of values and the way they are connected, and gives the total. It works with nanohenries, microhenries, millihenries or henries, and it shows the answer in the most readable unit. Type the inductor values, their unit and the way they are connected and the combined inductance appears at once, with a few related figures underneath, and you can copy the result with one tap. The sums run in your browser, so nothing you enter is uploaded.
Updated October 2026
How to use the Inductor Calculator
- 1Enter the inductor values, their unit and the way they are connected.
- 2Pick the units or options from the menus if the combined inductance tool offers them.
- 3Read the combined inductance in the large result box.
- 4Look at the extra rows for related figures.
- 5Press Copy result to keep the answer.
When you need the combined inductance
Electronics designers combine inductors to reach a value that is not sold as a single part, or to share a heavy current between several coils. Radio builders do the same when they wind and combine small coils for tuning circuits and filters.
The sums look just like the ones for resistors, which makes them easy to remember: series adds, parallel divides. The opposite holds for capacitors, where series makes the total smaller. This page keeps the inductor and resistor rule in one place.
How the combined inductance is worked out
In series the inductances simply add: L = L1 + L2 + … In parallel the reciprocals add: 1 ÷ L = 1 ÷ L1 + 1 ÷ L2 + … Three coils of 10, 22 and 47 millihenries in series give 79 mH. The same three in parallel give only 5.998 mH, smaller than the smallest one, just as with resistors.
Every answer on this page comes from that one rule, so you can check any result by hand with a calculator. The figures shown underneath, such as other units, are conversions of the same answer.
- Any number of inductors
- nH, µH, mH and H
- Series or parallel
Mistakes to avoid with combined inductance
The formulas assume the coils do not influence each other. When two coils sit close together, their magnetic fields link, and mutual inductance changes the total. Keep coils well apart, or use screened parts, if you want the simple formula to hold. Remember also the current rating of each coil.
On phone and computer
On a phone, type into the boxes one after another and read the combined inductance underneath; Copy result puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the combined inductance move. The inductor calculator works the same on both. Pair it with Capacitor Calculator and Resistor Calculator for the other parts, Resonant Frequency Calculator for tuned circuits, and Inductive Reactance Calculator for AC.
Features
- Series adds
- Parallel gives less than the smallest
- Keep coils apart
- Clear messages when the combined inductance inputs make no sense
- Copy the result with one tap
- Private: nothing is uploaded
Frequently asked questions
How do I calculate combined inductance?
In series the inductances simply add: L = L1 + L2 + … In parallel the reciprocals add: 1 ÷ L = 1 ÷ L1 + 1 ÷ L2 + … Three coils of 10, 22 and 47 millihenries in series give 79 mH. The same three in parallel give only 5.998 mH, smaller than the smallest one, just as with resistors.
What is the formula for combined inductance?
In series the inductances simply add: L = L1 + L2 + … In parallel the reciprocals add: 1 ÷ L = 1 ÷ L1 + 1 ÷ L2 + … The inductor calculator applies it exactly and rounds only the displayed answer to six significant figures.
Do inductors add like resistors?
Yes. In series they add directly, and in parallel the reciprocals add. This is the opposite of capacitors.
What is a henry?
The unit of inductance. A coil has an inductance of one henry if a current changing at one ampere per second produces one volt across it.
Why can mutual inductance spoil the result?
Because the magnetic field of one coil induces a voltage in the other, which acts like extra or reduced inductance depending on how they are oriented.
Is this inductor calculator free and private?
Yes. It is free, needs no account and runs in your browser, so the numbers you type are not uploaded or stored.