How do you convert between henry, millihenry, microhenry, and nanohenry? What are the conversion factors?
All SI inductance units use 1000x ratios: 1 H = 1000 mH = 1,000,000 μH = 1,000,000,000 nH = 10¹² pH. That means H→mH ×10³, mH→μH ×10³, μH→nH ×10³, nH→pH ×10³; reverse conversions divide by 1000. Simply move the decimal point 3 places—for example, 4.7 μH = 4700 nH = 0.0047 mH.
How many nanohenry (nH) are in 1 microhenry (μH)? How many millihenry (mH)?
1 μH = 1000 nH = 0.001 mH. Common inductor markings: output filter inductors for SMPS typically use 1 μH~100 μH, RF chokes 10 nH~1 μH, EMI common-mode inductors in mH range (e.g., 10 mH), and power transformer primary inductance can be several henries to tens of henries.
What is an abhenry (abH)? How do you convert it to henry?
abH (abhenry) is the inductance unit in the CGS electromagnetic unit system, 1 abH = 10⁻⁹ H = 1 nH (1 nanohenry). You'll see abH marked on older circuit diagrams, US military component datasheets, and some electromagnetic field literature—treat it directly as nH when converting: 1 abH = 1 nH = 0.001 μH.
What does 10 μH inductance mean? What size inductor is used where?
10 μH is a common value for SMD power inductors. Typical applications: DC-DC buck converter output filtering (1A~5A), mobile fast-charging power supply outputs, USB power filtering. Common inductance ranges: PCB trace ~1 nH/mm (about 1 nH parasitic inductance per mm), RF matching networks 1 nH~100 nH, SMPS power inductors 1 μH~100 μH, EMI common-mode inductors 1 mH~100 mH, power transformers 1 H~100 H.
How do you choose between mH and μH inductance units in circuits?
Based on operating frequency and current: high-current low-frequency (e.g., 50/60Hz line power filtering) uses mH~H range; mid-to-high frequency DC-DC SMPS (tens of kHz to several MHz) uses μH range; RF circuits (hundreds of MHz to GHz) use nH range. Larger inductance provides stronger opposition to current changes, but DC resistance (DCR) also increases, adding losses and heat—balance between ripple current and efficiency.
How do you calculate inductive reactance? What's its relationship to inductance?
Inductive reactance (AC impedance of an inductor) formula: XL = 2πfL, where f is frequency (Hz), L is inductance (H), XL in ohms (Ω). For example, a 10 μH inductor at 1 MHz has XL = 2×3.14×10⁶×10×10⁻⁶ ≈ 62.8 Ω, and at 100 MHz it reaches 6.28 kΩ—this is why small inductors act as chokes at RF. Always convert inductance to henries (H) and frequency to Hz before calculating reactance.
What do inductor markings 4R7, 100, 101 mean?
SMD inductors commonly use numeric markings: R represents a decimal point, units in μH. 4R7 = 4.7 μH; R10 = 0.1 μH = 100 nH; 100 = 10×10⁰ = 10 μH; 101 = 10×10¹ = 100 μH; 102 = 10×10² = 1000 μH = 1 mH; 223 = 22×10³ = 22,000 μH = 22 mH. For three-digit markings, the last digit is the power-of-10 multiplier (units in μH).
I keep mixing up capacitive reactance and inductive reactance formulas—any tips?
Capacitive reactance XC = 1/(2πfC) (C in farads F), inductive reactance XL = 2πfL (L in henries H). Memory trick: capacitors pass AC and block DC (higher frequency = lower reactance); inductors pass DC and block AC (higher frequency = higher reactance). Always convert to SI base units (F/H/Hz) before plugging into formulas—use this tool to convert μH/nH to H and pF/nF/μF to F first.
About how much parasitic inductance (in nH) do PCB traces have?
Typical surface-layer PCB traces have about 0.5~1 nH parasitic inductance per mm (depending on trace width and distance to reference plane); vias are about 0.5~1.5 nH. A 10 mm narrow trace has about 5~10 nH parasitic inductance, which significantly affects circuits above MHz frequencies. High-frequency decoupling capacitors need small 0402/0201 packages placed close to IC pins to keep lead inductance under 1 nH.
What factors affect transformer primary inductance?
Transformer primary inductance L = μ₀μrN²Ae/l_e, where μr is core relative permeability, N is primary turns, Ae is core effective cross-sectional area, l_e is effective magnetic path length. Typical SMPS transformer primary inductance: flyback converters hundreds of μH to several mH, LLC resonant converters tens to hundreds of μH, audio transformers several to tens of henries. Inductance directly affects magnetizing current magnitude and energy transfer capability.
Why is inductance conversion just simple multiply/divide by 1000?
Because the henry (H) is an SI derived unit, and mH/μH/nH/pH are all multiple units formed with SI prefixes (milli/micro/nano/pico). All SI prefixed units use 1000x ratios (10³ steps) with no offset like temperature conversions (Fahrenheit's +32 offset relative to Celsius). Inductance conversion is fundamentally a linear ratio transformation—just move the decimal point.
Will the inductance values I enter be uploaded? Is my data private?
No uploads at all. All conversion logic runs locally in your browser using pure client-side JavaScript. The inductance values you enter never make any network requests—servers cannot see your circuit parameters or design data. Inputs are cleared immediately when you close the page; no cookies or localStorage are used. Suitable for enterprise R&D, military electronics, repair work, teaching exams, and other data-sensitive scenarios.
