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Inductance Conversion Overview
The Inductance Conversion tool converts inductance values between henries and units with SI prefixes, including kilohenries, henries, millihenries, microhenries, nanohenries, and picohenries. Enter a value in any supported unit to display the equivalent values in the other units.
Inductance describes the relationship between changing current, magnetic flux linkage, and induced voltage. The SI unit of inductance is the henry, symbol H. In electronic circuits, mH, µH, and nH are much more common than whole henries.
How to Use the Inductance Converter
Find the input field for the inductance unit you already know.
Enter the numerical value.
Confirm the prefix and symbol, including uppercase and lowercase letters.
Read the converted results in the other units.
Keep enough significant digits for the component tolerance and intended calculation.
When selecting a real inductor, also verify the datasheet's measurement frequency, current, tolerance, and temperature conditions.
General Inductance Conversion Formula
Each inductance unit can be represented by a factor in henries. To convert from one unit to another:
Target value = Source value × Source factor in H / Target factor in H
For example, one millihenry equals 0.001 H and one microhenry equals 0.000001 H. Therefore:
1 mH = 0.001 / 0.000001 = 1000 µH
What Is Inductance?
An inductor stores energy in a magnetic field when current flows through it. A changing current produces a voltage across the inductance. Using the passive sign convention for an ideal inductor:
v(t) = L × di(t) / dt
Where:
v(t) = voltage across the inductor in volts
L = inductance in henries
di(t)/dt = rate of change of current in amperes per second
If induced electromotive force is written with a reference polarity opposing the current change, the same physical relationship may appear with a negative sign according to Lenz's law. The sign depends on the selected voltage and current reference directions.
Definition of the Henry
One henry is the inductance for which a current changing at one ampere per second corresponds to one volt across the inductor under the stated reference convention.
The henry can be expressed using other SI units:
1 H = 1 Wb/A
1 H = 1 V·s/A
1 H = 1 Ω·s
Wb/A is not a different-sized unit. One weber per ampere is exactly one henry.
SI Inductance Units and Prefixes
| Unit | Symbol | Equivalent in Henries |
|---|---|---|
| Exahenry | EH | 1018 H |
| Petahenry | PH | 1015 H |
| Terahenry | TH | 1012 H |
| Gigahenry | GH | 109 H |
| Megahenry | MH | 106 H |
| Kilohenry | kH | 103 H |
| Hectohenry | hH | 102 H |
| Dekahenry | daH | 10 H |
| Henry | H | 1 H |
| Decihenry | dH | 10-1 H |
| Centihenry | cH | 10-2 H |
| Millihenry | mH | 10-3 H |
| Microhenry | µH | 10-6 H |
| Nanohenry | nH | 10-9 H |
| Picohenry | pH | 10-12 H |
| Femtohenry | fH | 10-15 H |
| Attohenry | aH | 10-18 H |
Common Inductance Relationships
| Starting Unit | Equivalent Values |
|---|---|
| 1 H | 1000 mH = 1000000 µH = 1000000000 nH = 1000000000000 pH |
| 1 mH | 0.001 H = 1000 µH = 1000000 nH |
| 1 µH | 0.001 mH = 1000 nH = 1000000 pH |
| 1 nH | 0.001 µH = 1000 pH |
| 1 pH | 0.001 nH = 0.000001 µH |
pH, nH, and µH Conversion Chart
The following original chart provides a visual reference for commonly used small inductance units.
Prefix Capitalization Matters
SI symbols are case-sensitive. A change in capitalization can represent an enormous difference in value.
| Symbols | Meanings | Difference |
|---|---|---|
| MH and mH | Megahenry and millihenry | MH is 1000000000 times mH. |
| PH and pH | Petahenry and picohenry | PH is 1027 times pH. |
| H and hH | Henry and hectohenry | 1 hH = 100 H. |
| µH and uH | Microhenry and an ASCII substitute | µH is the proper SI form; uH is often used when µ is unavailable. |
In an inductance context, pH means picohenry. It should not be confused with pH as a measure of acidity in chemistry.
Worked Inductance Conversion Examples
Millihenries to Microhenries
Convert 4.7 mH to microhenries:
4.7 × 1000 = 4700 µH
The same value is 0.0047 H or 4700000 nH.
Microhenries to Millihenries
Convert 220 µH to millihenries:
220 / 1000 = 0.22 mH
The same value is 0.00022 H or 220000 nH.
Nanohenries to Picohenries
Convert 68 nH to picohenries:
68 × 1000 = 68000 pH
The same value is 0.068 µH.
Kilohenries to Henries
Convert 2.5 kH to henries:
2.5 × 1000 = 2500 H
Historical Non-SI Inductance Units
| Unit | Approximate SI Equivalent | Use |
|---|---|---|
| Abhenry, abH | 1 abH = 10-9 H | Historical electromagnetic CGS unit |
| Stathenry, stH | 1 stH ≈ 8.987552 × 1011 H | Historical electrostatic CGS unit |
| Weber per ampere | 1 Wb/A = 1 H | Equivalent SI expression |
Historical CGS units are rarely used in current component specifications. Confirm the original unit system before converting archival material.
Inductance Is Not Inductive Reactance
Inductance L is a component property measured in henries. Inductive reactance XL is the frequency-dependent opposition to AC and is measured in ohms:
XL = 2 × π × f × L
A unit conversion changes how the same inductance is expressed. It does not calculate reactance unless frequency is also provided.
Reactance Example
A 10 mH inductor has L = 0.01 H. At 1 kHz:
XL = 2 × π × 1000 × 0.01 = 62.832 Ω
At 10 kHz, the same ideal inductance has ten times the reactance, approximately 628.319 Ω.
Energy Stored in an Inductor
The ideal magnetic energy stored at current I is:
E = 0.5 × L × I2
Where E is energy in joules, L is inductance in henries, and I is current in amperes. Convert the inductance to henries before applying this equation.
Stored Energy Example
For L = 100 µH = 0.0001 H and I = 2 A:
E = 0.5 × 0.0001 × 22 = 0.0002 J = 0.2 mJ
Series and Parallel Inductors
For ideal uncoupled inductors in series:
LTOTAL = L1 + L2 + ... + LN
For ideal uncoupled inductors in parallel:
1 / LTOTAL = 1 / L1 + 1 / L2 + ... + 1 / LN
These simple formulas do not apply unchanged when the inductors are magnetically coupled. Mutual inductance and winding polarity must then be included.
Reading Inductor Datasheets
A converted nominal value is only one part of inductor selection. Check the datasheet for:
Tolerance: the permitted range around nominal inductance.
Test frequency: the frequency at which inductance is specified.
Test signal level: the small-signal voltage or current used for measurement.
DC resistance: winding resistance and copper loss.
Rated current: current associated with temperature rise or another stated criterion.
Saturation current: current at which inductance falls by a specified amount.
Self-resonant frequency: the frequency where parasitic capacitance changes behavior.
Q factor: a frequency-dependent measure related to reactance and loss.
Temperature range: operating and storage limits.
Manufacturers may define rated current and saturation current differently. Compare the stated test methods rather than relying only on the current number.
Why Measured Inductance Can Change
Core permeability changes with frequency, temperature, and DC bias.
Magnetic saturation reduces incremental inductance at high current.
Parasitic capacitance affects the measured result near self-resonance.
Fixture and lead inductance matter when measuring very small values.
Winding geometry and nearby conductive or magnetic materials can affect inductance.
Instrument test frequency and equivalent-circuit mode can change the reported value.
Typical Inductance Ranges and Applications
| Inductance Scale | Common Examples |
|---|---|
| pH to low nH | Package, lead, PCB trace, and interconnect parasitic inductance |
| nH to µH | RF matching, high-frequency chokes, and compact power inductors |
| µH to mH | Switching converters, filters, EMI chokes, and energy storage |
| mH to H | Audio filters, low-frequency chokes, sensors, relays, and transformers |
These ranges are broad orientation only. The correct value and construction depend on frequency, current, loss, size, voltage, and application requirements.
Common Inductance Conversion Mistakes
Confusing MH with mH or PH with pH.
Reading µH as mH.
Moving the decimal three places in the wrong direction.
Confusing inductance in henries with reactance in ohms.
Using a converted nominal value without considering tolerance.
Ignoring the frequency and current conditions used to specify inductance.
Using the uncoupled-inductor formula for magnetically coupled windings.
Assuming measured inductance remains constant near saturation or self-resonance.
Ignoring fixture and trace inductance when measuring nH or pH values.
Comparing current ratings from different manufacturers without reading their definitions.
Frequently Asked Questions
What is the SI unit of inductance?
The SI unit of inductance is the henry, symbol H.
How many microhenries are in one millihenry?
One millihenry equals 1000 microhenries.
How many nanohenries are in one microhenry?
One microhenry equals 1000 nanohenries.
How many picohenries are in one nanohenry?
One nanohenry equals 1000 picohenries.
Is Wb/A the same as H?
Yes. One weber per ampere is exactly one henry.
Is inductance the same as impedance?
No. Inductance is measured in henries. An ideal inductor's impedance is j2πfL and depends on frequency.
Why does an inductor value change with current?
Magnetic core permeability can change with DC bias, and the core may approach saturation. Datasheets commonly specify how much inductance decreases at a stated saturation current.
Why is measurement frequency important?
Core behavior, winding resistance, and parasitic capacitance are frequency-dependent. The measured inductance may therefore differ when test frequency changes.
Can I add inductors directly?
Uncoupled ideal inductors in series add directly. Magnetically coupled inductors require mutual-inductance and polarity analysis.
