Henry to Millihenry Converter
Quickly convert from Henry to Millihenry.
How to convert
Formula:
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Inductance conversion is essential in electronics, power engineering, and RF design.
Where is it used?
• Power Supplies — Inductors (1-1,000 μH) in switching regulators (buck/boost converters) store and release energy to smooth output voltage.
Examples:
• 1 H (henry) = 1,000 mH
• 1 mH = 1,000 μH
Inductance measures a conductor's ability to store energy in a magnetic field and resist rapid current change, so it is fundamental in power converters, filters, motor drives, and RF matching networks. Practical design work depends on conversions between henries, millihenries, microhenries, and nanohenries, from tiny RF inductors to high-inductance transformer and choke assemblies.
Inductance measures a conductor's ability to store energy in a magnetic field and oppose changes in current flow. The SI unit is the henry (H), defined as the inductance that produces 1 volt of EMF when current changes at 1 A/s. One millihenry (mH) = 0.001 H; one microhenry (μH) = 10⁻⁶ H; one nanohenry (nH) = 10⁻⁹ H.
Where is it used?
- Power Supplies — Inductors (1-1,000 μH) in switching regulators (buck/boost converters) store and release energy to smooth output voltage.
- RF & Wireless — Small inductors (1-100 nH) in antenna matching networks and RF filters; ferrite beads for EMI suppression.
- Audio & Signal Processing — Inductors in crossover networks (1-100 mH) separate frequency bands for speakers.
- Motors & Transformers — Motor windings have inherent inductance (mH range); power transformers use high inductance (H range) to transfer energy efficiently.
- Measurement — LCR meters measure inductance for quality control; impedance analyzers characterize inductors over frequency.
- EMI Suppression & Filtering — Common-mode chokes, ferrite components, and power-line inductors attenuate switching noise in chargers, motor drives, and data interfaces, helping equipment meet electromagnetic compatibility requirements.
Common Conversion Mistakes
Ignoring inductor self-resonant frequency (SRF)
Every inductor has parasitic capacitance between its windings. Above the self-resonant frequency (SRF), the component behaves capacitively, not inductively. A 100 μH inductor might only work correctly below 5-50 MHz. Always check SRF in RF applications.
Confusing inductance with resistance or impedance
Inductive reactance XL = 2πfL (in ohms), increasing with frequency. A 100 μH inductor has XL = 0.063 Ω at 100 Hz but 62.8 Ω at 100 kHz. Confusing inductance (H) with reactance (Ω) leads to circuit design errors.
Neglecting mutual inductance in coil proximity
Two inductors placed close together can couple magnetically. The effective inductance changes depending on coupling coefficient and relative orientation. In PCB design, placing inductors at right angles minimizes unwanted coupling.
Forgetting current limits cause core saturation
Inductors with magnetic cores (iron, ferrite) saturate when current exceeds rated value — inductance drops dramatically. A power inductor rated 2.2 μH / 3 A will behave like a short circuit at 10 A.
Quick Reference Table
| From | To |
|---|---|
| 1 H (henry) | 1,000 mH |
| 1 mH | 1,000 μH |
| 1 μH | 1,000 nH |
| 1 nH | 0.001 μH |
| Small RF choke | 1-100 nH |
| Switching regulator inductor | 1-100 μH |
| Audio crossover inductor | 1-10 mH |
| Power transformer | 1-100 H |
Frequently Asked Questions
What does an inductor actually do in a circuit?
An inductor resists changes in current — when current tries to increase, the inductor creates a back-EMF opposing the increase; when current tries to decrease, it sustains the current. This property is used to smooth current in power supplies, block high-frequency noise, and resonate with capacitors in filters and oscillators.
How do I calculate inductive reactance?
XL = 2πfL, where f is frequency in Hz and L is inductance in henries. At 50 Hz, a 1 H inductor has XL = 2π × 50 × 1 = 314 Ω. At 1 MHz, a 100 μH inductor has XL = 2π × 1,000,000 × 0.0001 = 628 Ω.
What is the LC oscillator and why does it matter?
An LC circuit (inductor + capacitor) resonates at f = 1/(2π√LC). This principle underlies all radio tuning, oscillators, and bandpass filters. A 1 μH inductor with a 25 pF capacitor resonates at exactly 1/(2π × √(10⁻⁶ × 25×10⁻¹²)) ≈ 31.8 MHz.
What is the energy stored in an inductor?
E = ½LI², where L is inductance in henries and I is current in amperes. A 10 mH inductor carrying 5 A stores ½ × 0.01 × 25 = 0.125 J. When current is suddenly interrupted, this energy must go somewhere — causing voltage spikes that can damage transistors. Always add flyback diodes across inductive loads.
Why does inductor value fall when the core saturates?
In a magnetic-core inductor, inductance depends on the core permeability. As current rises, the magnetic material approaches saturation, its effective permeability drops, and the inductance decreases sharply. That causes current ripple to increase and can lead to overheating or switching spikes in power converters. Designers therefore choose inductors with saturation-current margin above the expected peak current.
Sources & Standards
- International Electrotechnical Commission (IEC)
- Institute of Electrical and Electronics Engineers (IEEE)
- National Institute of Standards and Technology (NIST)
- Erickson, R. W. & Maksimovic, D. — Fundamentals of Power Electronics, 3rd ed. (Springer)
Reviewed by The Unit Hub Editorial Team · March 2026