The inductance converter above moves a single value between every unit of inductance you are likely to meet: the SI henry and its decimal prefixes, plus the electromagnetic CGS abhenry and the electrostatic stathenry that still appear in older textbooks and legacy test equipment manuals. Type a number, pick the two units, and the answer appears immediately — along with the same quantity expressed in the four units engineers reach for most often.
Arb Digital builds and maintains a large library of free engineering and unit tools, and this one exists because inductance is the quantity where prefix mistakes hurt most. A capacitor mislabelled by a factor of a thousand usually just shifts a filter corner. An inductor off by the same factor can saturate, overheat, or turn a working switching regulator into a component that fails on the bench. Getting the prefix right is not a formality.
What This Inductance Converter Does
Inductance measures how strongly a conductor opposes a change in the current flowing through it. When current through a coil changes, the coil's own magnetic field induces a voltage that pushes back against that change. The constant of proportionality between the rate of current change and the induced voltage is the inductance, and its SI unit is the henry, named after Joseph Henry. One henry means that a current changing at one ampere per second induces one volt.
A henry is a very large unit in practice. Real components used in radio, power conversion and signal filtering land between a few picohenries — the parasitic inductance of a short PCB trace — and a few hundred millihenries for a mains-frequency choke. That range spans about twelve orders of magnitude, which is exactly why decimal prefixes exist and exactly why converting between them by hand invites error. This tool removes the counting of zeros entirely.
The result hero shows your requested conversion. The four-item grid underneath always shows the same physical quantity in henries, millihenries, microhenries and nanohenries at the same time, so you can see where your value sits on the practical scale rather than reading one isolated number.
How to Use It
- Enter your inductance value. Any positive or negative decimal works, and scientific notation such as 4.7e-6 is accepted for very small values.
- Choose the unit you are converting from. This is the unit printed on your datasheet, schematic, or meter display.
- Choose the unit you want. Pick whatever your calculation or BOM needs.
- Read the result hero. It updates live as you type — there is no need to press anything, though the Convert button is there for keyboard and screen-reader users.
- Use Swap units to reverse the direction of the conversion without retyping anything.
The Formula: How Inductance Conversion Is Calculated
Every unit conversion in this tool is a two-step multiplication through a single base unit. The value is first converted to henries by multiplying by the source unit's factor, then converted out of henries by dividing by the destination unit's factor:
result = value × factor(from) ÷ factor(to)
Because the SI prefixes are pure powers of ten, the factors for milli, micro, nano and pico are exactly 10⁻³, 10⁻⁶, 10⁻⁹ and 10⁻¹² with no rounding at any point. The prefix definitions are set out in the BIPM SI Brochure, and the henry itself is a coherent derived unit equal to one weber per ampere, or equivalently kg·m²·s⁻²·A⁻².
The two CGS units are different in kind. The abhenry belongs to the electromagnetic CGS system and equals exactly 10⁻⁹ H — one nanohenry — which makes it the only historical unit here that maps onto a clean SI prefix. The stathenry belongs to the electrostatic CGS system and equals roughly 8.987551787 × 10¹¹ H. That awkward number is not arbitrary: it is the square of the speed of light in centimetres per second divided by 10⁹, which is why it changed from a measured value to an exact one when the metre was redefined in terms of the speed of light. The conversion factors used here follow NIST Special Publication 811, the standard American reference for SI usage and unit conversion.
Reference Table: Every Supported Unit
Each factor below is the number of henries in one of that unit. Multiply by the factor to get henries; divide by it to go the other way.
- henry (H) — 1 (SI base for this quantity)
- kilohenry (kH) — 1 × 10³ H
- millihenry (mH) — 1 × 10⁻³ H
- microhenry (µH) — 1 × 10⁻⁶ H
- nanohenry (nH) — 1 × 10⁻⁹ H
- picohenry (pH) — 1 × 10⁻¹² H
- weber per ampere (Wb/A) — 1 H exactly; this is the definition of the henry written out
- abhenry (abH) — 1 × 10⁻⁹ H, identical in size to the nanohenry
- stathenry (statH) — 8.987551787 × 10¹¹ H
Reading Inductor Markings Without Getting Burned
Surface-mount inductors are usually marked with a three-digit code where the first two digits are significant figures and the third is a power of ten, with the implied unit being microhenries. A part marked 101 is 10 × 10¹ = 100 µH. A part marked 4R7 uses R as a decimal point and means 4.7 µH. Neither marking tells you the unit explicitly, which is the trap: you have to know the series convention before you can trust the number, and some RF series use nanohenries instead.
The safest habit is to convert whatever you read into a single working unit — microhenries is the usual choice for switching converters — before comparing parts. Two datasheets that quote 0.47 mH and 470 µH are describing exactly the same component, but a quick visual scan of a BOM will not always tell you that. Running everything through one unit removes the ambiguity, and it is the same discipline that stops mistakes in the capacitance converter, where the µF/nF/pF split causes identical confusion.
Why Parasitic Inductance Is Measured in Nanohenries
Every conductor has inductance, including one you never intended to be an inductor. A straight PCB trace one centimetre long over a ground plane typically contributes on the order of several nanohenries, and a through-hole component lead adds a similar amount. In a slow analogue circuit that is invisible. In a switching regulator running at a megahertz or more, those nanohenries multiply against very fast current transitions and produce real voltage spikes, because the induced voltage depends on the rate of change of current, not the current itself.
This is why decoupling capacitors are placed physically close to the pins they serve. The goal is not to shorten the wire for resistance reasons — the resistance of a centimetre of copper is negligible — but to minimise the loop inductance of the path. Once you start thinking in nanohenries per centimetre, layout stops being a cosmetic exercise and becomes part of the electrical design. Converting your inductance budget into nanohenries makes that trade-off visible.
Self Inductance, Mutual Inductance and Why the Unit Is the Same
Self inductance describes a coil opposing changes in its own current. Mutual inductance describes one coil inducing a voltage in a second, physically separate coil. Both are measured in henries, because both express the same underlying ratio of induced volts to amperes per second. A transformer datasheet may quote primary inductance, leakage inductance and mutual inductance in the same units on the same line, and they mean quite different things about the same component.
Coupling coefficient, usually written k, links them: the mutual inductance between two coils is k times the square root of the product of their individual inductances, with k ranging from zero for magnetically isolated coils to one for perfect coupling. Because k is dimensionless, no unit conversion is involved — but the two self-inductance values feeding the calculation must be in the same unit before you multiply them, which is precisely the step this converter is for.
Inductance in Resonance and Filter Design
The most common place an inductance value gets used is a resonant frequency calculation, where the resonant frequency of an LC circuit equals 1 divided by 2π times the square root of L times C. That formula only works in coherent SI units: L in henries, C in farads, result in hertz. Feeding it microhenries and picofarads without converting produces an answer wrong by many orders of magnitude, and because the square root softens the error, the result can look plausible enough to survive a quick sanity check.
The practical workflow is to convert both the inductance and the capacitance to base SI units first, run the formula, and only then present the answer in a convenient unit. If you need to move between hertz, kilohertz, megahertz and gigahertz afterwards, our frequency converter handles that side. For the reactance side of the calculation, remember that inductive reactance rises linearly with frequency while capacitive reactance falls, which is why an inductor that behaves well at mains frequency can be a poor choice at radio frequency.
Where Inductance Sits Among the Other Electrical Quantities
Inductance is one member of a family of electrical quantities that share the same conversion logic but describe entirely different physics. Resistance opposes current itself and is handled by our resistance converter. Capacitance stores energy in an electric field rather than a magnetic one. Charge, the quantity that actually flows, has its own electric charge converter. The magnetic field an inductor produces is a separate quantity again, covered by the magnetic field converter.
Keeping these distinct matters because their CGS legacy units look confusingly similar — abhenry, abfarad, abohm and abampere all share a prefix while measuring completely unrelated things. This tool deliberately restricts its unit list to inductance only, so a cross-quantity conversion is structurally impossible rather than merely discouraged.
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Web Development Services Browse All Free ToolsCommon Mistakes to Avoid
- Confusing mH with µH — a factor of one thousand, and the single most common inductance error in a bill of materials.
- Assuming the abhenry is a big unit because the CGS name sounds imposing. It is exactly one nanohenry.
- Mixing units inside the LC resonance formula — convert to henries and farads first, always.
- Ignoring parasitic inductance in high-speed layouts, where a few nanohenries of trace can dominate the intended component.
- Reading an SMD three-digit code as a literal number — 101 means 100 µH, not 101 of anything.
Related Free Tools From Arb Digital
Pair this with the capacitance converter for the other half of a resonant circuit, the resistance converter for ohms and its prefixes, and the electric charge converter for coulombs and amp-hours. For field strength work, use the magnetic field converter, and for anything involving watts see the power converter. The full free online tools hub lists every converter we publish.
Frequently Asked Questions
The henry, symbol H. One henry is defined as one weber per ampere, which means a current changing at one ampere per second through the coil induces one volt across it.
Exactly one thousand. Milli is ten to the power minus three and micro is ten to the power minus six, so 1 mH equals 1,000 µH and 0.47 mH equals 470 µH.
Yes. The abhenry, the electromagnetic CGS unit of inductance, equals exactly ten to the power minus nine henries, which is identical to one nanohenry.
In the common surface-mount coding scheme the R acts as a decimal point and the implied unit is microhenries, so 4R7 means 4.7 µH. Always check the series convention, because some radio-frequency ranges use nanohenries instead.
The stathenry comes from the electrostatic CGS system, where the conversion to SI involves the square of the speed of light. That gives roughly 8.987551787 times ten to the eleventh henries per stathenry.
Yes. The standard resonance formula requires inductance in henries and capacitance in farads. Using microhenries and picofarads directly will give an answer wrong by many orders of magnitude.
Physical self inductance is always positive. Negative values appear only in circuit models and in mutual inductance terms, where the sign records the relative winding direction of two coupled coils rather than a negative physical property.
