SMD Resistor Code Calculator Formula

Understand the math behind the smd resistor code calculator. Each variable explained with a worked example.

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Formulas Used

Resistance

resistance = base_val * pow(10, mult_exp)

Resistance (k)

resistance_k = base_val * pow(10, mult_exp) / 1000

Variables

VariableDescriptionDefault
digit1First Digit4
digit2Second Digit7
mult_expThird Digit (10^x)2
base_valDerived value= digit1 * 10 + digit2calculated

How It Works

SMD Resistor Code

3-Digit Format: XYZ

  • X = first digit
  • Y = second digit
  • Z = number of zeros

    • Example: 472 = 47 x 10^2 = 4700 ohms

    Worked Example

    SMD code 472.

    digit1 = 4digit2 = 7mult_exp = 2
    1. 01Base = 47
    2. 02Multiplier = 100
    3. 03Resistance = 4700 ohms = 4.7k

    Frequently Asked Questions

    What does R mean in SMD codes?

    R is a decimal point. 4R7 = 4.7 ohms.

    What is EIA-96?

    A lookup-table code system for 1% SMD resistors.

    How small are SMDs?

    From 0201 (0.6x0.3 mm) to 2512 (6.3x3.2 mm).

    Learn More

    Guide

    Understanding Resistor Color Codes

    Learn how to read resistor color codes for 4-band, 5-band, and 6-band resistors. Includes the color chart, tolerance bands, and tips for quick identification.

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    Open SMD Resistor Code Calculator