SMD Inductor Code Calculator (EIA Standard Codes)

Decode 3-digit and alphanumeric SMD chip inductor markings into nanohenries (nH) and microhenries (µH) per EIA standard marking codes.

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Convert Inductance to Code

Target Inductance

Tolerance

Invalid SMD code format. Check input value or character standard.

For ±20% tolerance, the 'M' letter is optional in actual markings.

RESULTS

Rated Inductance

Inductor Tolerance

Tolerance Range

Standard Class

Input Parameters Specification

SMD Inductor CodeAlphanumeric characters marked directly on the face of the SMT inductor core.

Unit DefinitionStandard baseline measurements evaluated in Microhenries (µH) or Nanohenries (nH).

Tolerance StandardPrecision tolerances representing J (±5%), K (±10%), M (±20%), or D (±0.3 nH).

Standard ScalingDetermines the decimal point indicator based on 'R' (micro) or 'N' (nano) structures.

Practical Operational Examples

101 Standard Inductor (100 µH)

Decodes as 10 × 10^1 = 100 µH. Typically found in filtering power lines of circuit boards.

4R7 Power Choke (4.7 µH)

The letter 'R' acts as a decimal point, yielding 4.7 µH. Essential for DC-DC buck converters.

22N Sub-Micro Choke (22 nH)

The letter 'N' acts as a decimal point, yielding 22 nH. Used extensively in RF matching networks.

123J High-Precision Choke (12 mH)

Decodes as 12 × 10^3 µH = 12,000 µH (12 mH) with a ±5% precision rating.

Diagrams & Theory

Surface Mount Device (SMD) inductors are wire-wound or multilayer coils encapsulated inside a protective ferrite magnetic shield. Due to their compact size, they utilize printed character sets instead of colored rings.

Their leadless direct-solder design minimizes equivalent series resistance (ESR), preventing unwanted high-frequency noise spikes in switching regulator circuits.

Formulas & Mathematical Logic

For 3-Digit System: Inductance = (Digit 1 × 10 + Digit 2) × 10^Multiplier (in µH)

For 'R' Notation: Represents decimal placement under microhenries scale (µH)

For 'N' Notation: Represents decimal placement under nanohenries scale (nH)

Step-by-Step Example

Example: Decodifying an "101" SMD Inductor (Shown in the visualizer above)

Step 1: Extract the first two numbers as base values: "10".

Step 2: Identify the third digit as multiplier: "1" (representing 10^1 = 10).

Step 3: Multiply base value by multiplier: 10 × 10 = 100 µH.

Step 4: Compute tolerance range: Standard ±20% yields (80 µH ... 120 µH).

How to Use This Calculator

Locate the printed alphanumeric characters on the face of the active SMD inductor.

Type the characters directly into the input field on the dark visualizer graphic.

The calculated inductance rating, standard, and tolerances are computed in real-time.

To reverse-calculate, simply enter targeted specifications into the manual inputs below.

About This Calculator

Evaluate SMD active components with high precision.

This light, self-contained tool supports 3-digit, decimal micro, and decimal nano coding systems.

Using proper SMD components reduces circuit trace footprints while significantly improving line filter efficiency in compact smartphone and compute board applications.

EIA StandardsSupports standard E6, E12, and high-frequency RF standards.

Visual VerificationThe round inductor graphic adapts to inputs dynamically.

Decimal HandlingFully resolves 'R' (micro) and 'N' (nano) decimal indicators.

Privacy FirstUses self-contained JS calculations to run seamlessly without trackers.

Tip: Always verify power choke parameters using an LCR bridge before final assembly.

Frequently Asked Questions

1. What is an SMD inductor and how does it function?

An SMD inductor is a wire coil wrapped around a ferrite drum, directly soldered to PCB tracks to smooth out high-frequency switching current spikes.

2. What does the character 'R' mean in inductor markings?

The character 'R' represents a decimal point scaled in microhenries (µH). For example, "4R7" indicates 4.7 µH.

3. What does the character 'N' mean in inductor markings?

The character 'N' represents a decimal point scaled in nanohenries (nH). For example, "22N" indicates 22 nH.

4. How is tolerance evaluated if no code letters are specified?

When code markers do not specify precision limits (like J, K, or M), the device falls back to standard ±20% baseline tolerances.

5. What is the difference between power inductors and RF inductors?

Power inductors have high saturation currents designed to handle buck/boost regulators, whereas RF inductors feature high Q-factors designed to filter high-frequency communications.

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About this tool

SMD Inductor Code Calculator (EIA Standard Codes) is a free online calculator tool. Use it to get instant, accurate results for your electronics calculations.