Resistor Color Code Calculator
Decode 4-band resistor color bands into exact Ohms, kilohms, or megohms with tolerance rating.
Nominal resistance is 1.0 kΩ with ±5% tolerance.
How to Read Axial Resistor Color Bands & SMD Markings
- Choose your component topology: 4-Band (standard hobbyist/commercial), 5-Band (precision metal film), 6-Band (high-reliability with temperature coefficient), Reverse Solver, or SMD Chip Decoder.
- Match physical resistor band colors from left to right. Notice that the tolerance band (Gold, Silver, or Brown) is spaced slightly farther apart at the right termination edge.
- The laboratory displays the nominal resistance (Ω, kΩ, MΩ), operational min/max range based on tolerance, closest IEC 60063 E-series value, and temperature coefficient (ppm/K).
IEC 60062 & IEC 60063 Mathematical Specifications
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4-Band Calculation:
R = [(Band₁ × 10) + Band₂] × Multiplier ± Tolerance% -
5-Band Precision:
R = [(Band₁ × 100) + (Band₂ × 10) + Band₃] × Multiplier ± Tolerance% -
6-Band Temp Coefficient: TCR (Temperature Coefficient of Resistance) indicates resistance drift in parts-per-million per Kelvin:
ΔR = R₀ × TCR × ΔT / 10⁶. -
SMD 3-Digit Code (EIA): First 2 digits are significant numbers, 3rd digit is the 10ⁿ multiplier (e.g.,
472 = 47 × 10² = 4,700 Ω = 4.7 kΩ). -
SMD 4-Digit Code (EIA ±1%): First 3 digits are significant numbers, 4th digit is the multiplier (e.g.,
1002 = 100 × 10² = 10 kΩ). -
SMD R-Notation: The letter "R" acts as a decimal point for fractional values (e.g.,
4R7 = 4.7 Ω,0R22 = 0.22 Ω,R050 = 0.05 Ω).
Verified Engineering Worked Traces
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4-Band Example: Yellow - Violet - Red - Gold
Digits: 4, 7 | Multiplier: 10² (100) | Tolerance: ±5%
Calculation:47 × 100 = 4,700 Ω = 4.7 kΩ ±5%(Operational band: 4,465 Ω to 4,935 Ω). -
5-Band Precision Example: Brown - Black - Black - Brown - Brown
Digits: 1, 0, 0 | Multiplier: 10¹ (10) | Tolerance: ±1%
Calculation:100 × 10 = 1,000 Ω = 1.0 kΩ ±1%(Operational band: 990 Ω to 1,010 Ω). -
EIA-96 High-Precision SMD Example: Marking
01C
Code 01 = 100 base value; Letter C = 100 multiplier.
Result:100 × 100 = 10,000 Ω = 10 kΩ (±1%).
Practical Applications & Bench Verification
- Validating salvaged and unlabelled through-hole resistors before breadboard circuit prototyping.
- Selecting accurate pull-up, pull-down, and current-limiting resistors for microcontrollers (ESP32, Arduino, STM32).
- Verifying precision feedback loops and op-amp divider networks where ±0.1% or ±0.5% tolerances are required.
- Decoding compact surface-mount components (SMD 0805, 0603, 1206) during PCB rework and board-level repair.
Frequently Asked Questions
Which band do I read first on a physical resistor?
Look for the tolerance band (typically Gold ±5%, Silver ±10%, or Brown ±1%), which is separated by a wider physical gap from the other color bands. Always begin reading from the opposite end where bands are clustered closer together.
Why are resistors manufactured in specific values like 4.7k or 2.2k instead of round numbers like 5k?
Resistors follow standard logarithmic preferred series defined by IEC 60063 (E12, E24, E96). Each step represents an equal percentage step ensuring that any value within the manufacturing tolerance overlaps cleanly with neighboring values without gaps.
What does TCR (Temperature Coefficient) mean on 6-band resistors?
TCR is measured in ppm/°C (parts per million per degree Celsius). A TCR of 50 ppm/K means a 10 kΩ resistor will change value by no more than 0.5 Ω for every 1°C deviation from room temperature (25°C).