Inductance units — µH, mH and nH
Physical size scales with inductance × current². A 100 mH inductor is a transformer core; 100 nH is a curl of wire.
Inductance is what stores energy in magnetic fields. Values span from femto- and picohenries (bond wires and IC packages) through nanohenries (PCB traces, RF matching) into microhenries and millihenries (power converters) and up to henries (line-frequency inductors, ballasts).
The exact factors
1 H = 10³ mH = 10⁶ µH = 10⁹ nH = 10¹² pH > Typical PCB trace: ~1 nH/mm above a ground plane > Toroidal inductor 22 mm diameter, 20 turns on -26 mix: ~30 µH
Where each dominates
pH, nH: package parasitics, RF matching, PCB decoupling loops. µH: switch-mode converters, EMI chokes. mH: audio filters, PFC boost inductors. H: line-frequency ballasts, current-limiting reactors.
Worked example — buck converter
12 V → 3.3 V buck, 500 kHz, 3 A output, 30% ripple. L = (V_in − V_out) × D / (Δi × f) = (12 − 3.3) × 0.275 / (0.9 × 500 000) = 5.3 µH. A 4.7 µH standard inductor with 4 A saturation rating fits — a 5.3 nH bead is 1000× smaller and has effectively no inductance for this job.
Recap
Match the value and the physical scale — µH inductors are hardware, nH inductors are geometry.
Try the converters mentioned in this article
FAQ
How do I estimate PCB trace inductance?+
About 1 nH per mm for traces over a ground plane, more for isolated wires. A 25 mm trace is ~25 nH — significant for GHz signals.
Do inductors have a Q?+
Yes — quality factor Q = ωL/R. Higher Q means lower loss at the operating frequency.
This article was written by The Turbo Unit Converter engineering desk (Applied metrology & engineering units) and last reviewed on 2026-07-07 against NIST SP 811 and the BIPM SI Brochure. Read our full editorial policy.