Inductor Color Code & SMD Calculator
Decode 4-band and 5-band axial RF molded inductors and 3-digit SMD power inductor codes in microhenries (µH) with tolerance ratings.
Engineering Principles & Formulas
Molded axial RF chokes and power inductors use color bands based on the EIA standard. Critical Distinction: While resistor color codes calculate base resistance in Ohms (\(\Omega\)), inductor color bands calculate inductance with microhenries (µH) as the base unit:
SMD Inductor Marking Codes
Surface mount wirewound and multilayer inductors (e.g. 0805, 1210, or shielded power chokes) typically use a 3-character code where "R" represents the decimal point:
- 4R7 = 4.7 µH
- R47 = 0.47 µH
- 100 = 10 × 10⁰ = 10 µH
- 101 = 10 × 10¹ = 100 µH
- 102 = 10 × 10² = 1,000 µH = 1.0 mH
Reference Table & Standards
| Color | Significant Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×10^0 | ±20% |
| Brown | 1 | ×10^1 | ±1% |
| Red | 2 | ×10^2 | ±2% |
| Orange | 3 | ×10^3 | ±3% |
| Yellow | 4 | ×10^4 | ±4% |
| Green | 5 | ×10^5 | — |
| Blue | 6 | ×10^6 | — |
| Violet | 7 | ×10^7 | — |
| Gray | 8 | — | — |
| White | 9 | — | — |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
Continuous Calculation Chain
Electronics engineering workflows naturally connect. Continue your calculation with pre-filled parameters:
Compare axial inductor color codes with standard resistor bands.
Ensure PCB power traces can conduct switching inductor currents.
Calculate DC resistance (DCR) copper losses across the inductor winding.
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Frequently Asked Questions
How do I distinguish an axial inductor from a resistor?
Axial inductors are usually coated in a pale green, turquoise, or light blue epoxy body with slightly thicker body tapers at the ends, whereas standard carbon film resistors typically have tan or beige bodies, and metal film resistors are light blue with 5 bands.
What is DCR and why does it matter for power inductors?
DC Resistance (DCR) is the electrical resistance of the copper wire winding inside the inductor. High DCR creates I²R heat losses and drops output voltage in buck/boost switching regulators.