Henry is the SI unit of inductance.
Henrys to Millihenrys Converter — H to mH
Convert Henry (H) to Millihenry (mH) using the exact conversion factor (1 henry = 1,000 millihenry). See the formula, worked examples, conversion table, history, and common uses.
Henrys to Millihenrys converter
Converter
Electricity Converter
Convert electrical units by family and calculate voltage, current, resistance, power, and energy with context values.
Context values
Some unit families need one extra value for a physically accurate result.
Millihenry is 0.001 henry units.
Result = input x 1 / 0.001.
Electrical units in the same family convert directly.
Reserved above the conversion cards and below the converter.
About Converting Henrys to Millihenrys
Henry and Millihenry both belong to the electricity family — voltage, current, resistance, power, or energy — units that show up constantly when working across the different standards used by household wiring (120V/240V depending on region), automotive electrical systems (12V/24V), and electronics design. Henry is most often used for inductor and transformer ratings in electronics.
Formula
millihenrys = henrys × 1000
This factor comes from each unit's defined relationship to the category's base unit: 1 henry equals 1 base unit, and 1 millihenry equals 0.001 base units, so dividing one by the other gives the direct henry-to-millihenry factor of 1000.
Simple example
1 H × 1000 = 1,000 mH
1 henry = 1,000 millihenrys.
Real-world example
120 H × 1000 = 120,000 mH
120 henrys = 120,000 millihenrys.
Conversion table
| Henry (H) | Millihenry (mH) |
|---|---|
| 1 H | 1,000 mH |
| 5 H | 5,000 mH |
| 12 H | 12,000 mH |
| 24 H | 24,000 mH |
| 120 H | 120,000 mH |
| 240 H | 240,000 mH |
Reverse conversion: Millihenry to Henry
1 mH × 0.001 = 0.001 H
1 millihenry = 0.001 henrys.
henrys = millihenrys × 0.001
For a page dedicated to this direction, see Millihenry to Henry.
Understanding the Henry
Henry (H) measures electrical inductance. The SI derived unit of electrical inductance, equal to one volt-second per ampere. It is classified as a SI derived unit.
Where it's used: Universal — SI derived unit used worldwide
Uses of the Henry today
- Inductor and transformer ratings in electronics
- Motor and generator design calculations
- Circuit filtering and signal-processing design
History of the Henry
The henry is named after Joseph Henry (1797–1878), an American scientist who discovered the electromagnetic phenomenon of self-inductance independently of, and at roughly the same time as, Michael Faraday's related discoveries in England.
Historical origin. Henry was not the invention of a single named person; it developed through the process described above.
Understanding the Millihenry (mH)
Millihenry is 0.001 henry units.
Henry — sources
- BIPM SI Brochure, 9th edition — Definition of the henry as a coherent SI derived unit.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many millihenrys are in 1 henry?
1 henry equals 1,000 millihenrys, using the exact defined conversion factor rather than an estimate.
How do I convert henry to millihenry?
Multiply the henry value by 1000. The converter above does this instantly to whatever precision you set.
How do I convert millihenry back to henry?
Use the reverse factor: 1 millihenry equals 0.001 henrys. You can also use the swap control in the converter above to flip the direction instantly.
What is a henry?
Henry (H) measures electrical inductance. The SI derived unit of electrical inductance, equal to one volt-second per ampere. It is classified as a SI derived unit.
What is a millihenry?
Millihenry (mH) is a unit of electricity.
Is the henry to millihenry conversion exact?
Yes. Both henry and millihenry are defined by fixed standards rather than physical artifacts, so the factor of 1000 used above is exact to as many digits as you choose to display.
Where is the henry still used today?
Universal — SI derived unit used worldwide
What's the difference between voltage, current, and resistance?
Voltage (volts) is the electrical potential difference driving current through a circuit. Current (amperes) is the rate of flow of electric charge. Resistance (ohms) is how much a component opposes that flow. They're related by Ohm's law (V = I × R), but they are distinct physical quantities, and this page converts between units of just one of them.