Resistor Calculator
Calculate series and parallel resistance combinations and decode resistor color bands.
Calculator Mode
Enter resistance values in ohms, separated by commas
Series Total
Resistor Values (3)
Series Circuit Info
In a series circuit, resistors are connected end-to-end.
The total resistance is the sum of all resistances.
Current is the same through all resistors.
What Is the Resistor Color Code?
The resistor color code is a standardized system using colored bands to indicate a resistor's value and tolerance. This system allows technicians to quickly identify resistance values without needing measuring equipment.
| Color | Digit Value | Multiplier | Tolerance | Temp Coefficient |
|---|---|---|---|---|
| Black | 0 | ×1 (10⁰) | — | 250 ppm/K (U) |
| Brown | 1 | ×10 (10¹) | ±1% (F) | 100 ppm/K (S) |
| Red | 2 | ×100 (10²) | ±2% (G) | 50 ppm/K (R) |
| Orange | 3 | ×1k (10³) | ±0.05% (W) | 15 ppm/K (P) |
| Yellow | 4 | ×10k (10⁴) | ±0.02% (P) | 25 ppm/K (Q) |
| Green | 5 | ×100k (10⁵) | ±0.5% (D) | 20 ppm/K (Z) |
| Blue | 6 | ×1M (10⁶) | ±0.25% (C) | 10 ppm/K (Z) |
| Violet | 7 | ×10M (10⁷) | ±0.1% (B) | 5 ppm/K (M) |
| Gray | 8 | ×100M (10⁸) | ±0.01% (L) | 1 ppm/K (K) |
| White | 9 | ×1G (10⁹) | — | — |
| Gold | — | ×0.1 (10⁻¹) | ±5% (J) | — |
| Silver | — | ×0.01 (10⁻²) | ±10% (K) | — |
Reading Color Bands
Where:
- 1st/2nd/3rd= Significant digits (0-9)
- Multiplier= Power of 10 to multiply by
- Tolerance= Accuracy percentage
4-Band, 5-Band, and 6-Band Resistors
Resistors come in different band configurations depending on precision requirements.
| Type | Band 1 | Band 2 | Band 3 | Band 4 | Band 5 | Band 6 | Typical Tolerance |
|---|---|---|---|---|---|---|---|
| 4-band | 1st digit | 2nd digit | Multiplier | Tolerance | — | — | ±5% or ±10% |
| 5-band | 1st digit | 2nd digit | 3rd digit | Multiplier | Tolerance | — | ±1% or ±2% |
| 6-band | 1st digit | 2nd digit | 3rd digit | Multiplier | Tolerance | Temp coef | ±1% or better |
Which direction to read: The tolerance band (usually gold, silver, or a wider gap) is always last. Start reading from the opposite end. On 5/6-band resistors, bands are grouped more closely on one side—start from that side.
Standard Resistor Values (E-Series)
Resistors are manufactured in standard values based on the E-series. Higher E-numbers provide more values and tighter tolerances.
| Series | Values per Decade | Tolerance | Values (first decade) |
|---|---|---|---|
| E6 | 6 | ±20% | 10, 15, 22, 33, 47, 68 |
| E12 | 12 | ±10% | 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 |
| E24 | 24 | ±5% | 10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82, 91 |
| E48 | 48 | ±2% | Includes E24 plus intermediate values |
| E96 | 96 | ±1% | Includes E48 plus more values |
| E192 | 192 | ±0.5% | Finest standard series |
Decade scaling: Each series value exists in every decade (×1, ×10, ×100, etc.). So E12 gives you 10Ω, 100Ω, 1kΩ, 10kΩ, etc., and also 12Ω, 120Ω, 1.2kΩ, etc.
Types of Resistors
Different resistor technologies suit different applications.
| Type | Tolerance | Power Range | Best For | Temperature Stability |
|---|---|---|---|---|
| Carbon film | ±5% | 0.125-2W | General purpose, low cost | Moderate |
| Metal film | ±1% | 0.125-1W | Precision circuits | Good |
| Metal oxide | ±5% | 0.5-5W | High power, surge protection | Good |
| Wirewound | ±1-5% | 1-300W | High power, precision | Excellent |
| Thick film (SMD) | ±1-5% | 0.0625-1W | Surface mount circuits | Good |
| Thin film (SMD) | ±0.1% | 0.0625-0.25W | High precision SMD | Excellent |
Combining Resistors in Series and Parallel
When a specific resistance value isn't available, you can combine resistors in series or parallel to achieve it.
| Configuration | Formula | Result | Use Case |
|---|---|---|---|
| Series | Rtotal = R₁ + R₂ + R₃ + ... | Higher than any individual | Increase resistance |
| Parallel (2 resistors) | Rtotal = (R₁ × R₂) / (R₁ + R₂) | Lower than smallest | Decrease resistance |
| Parallel (n equal) | Rtotal = R / n | R divided by count | Equal resistors |
| Parallel (general) | 1/Rtotal = 1/R₁ + 1/R₂ + ... | Use reciprocals | Any combination |
Practical tip: Two equal resistors in parallel = half the value. A 10kΩ and 10kΩ in parallel = 5kΩ. This also doubles the power handling capacity.
Parallel Resistor Formula
Where:
- R1, R2, R3= Individual resistor values
- R_total= Combined equivalent resistance
SMD Resistor Codes
Surface-mount (SMD) resistors use numeric codes instead of color bands due to their small size.
| Code Format | Meaning | Example | Value |
|---|---|---|---|
| 3-digit | AB × 10C | 472 | 47 × 10² = 4.7kΩ |
| 3-digit | AB × 10C | 103 | 10 × 10³ = 10kΩ |
| 3-digit | AB × 10C | 4R7 | 4.7Ω (R = decimal) |
| 4-digit | ABC × 10D | 4702 | 470 × 10² = 47kΩ |
| EIA-96 | Code + letter | 01C | 100Ω (lookup table) |
Zero and low values: "0" or "000" means 0Ω (jumper). "R10" means 0.10Ω. The "R" indicates decimal point position.
Worked Examples
Read a 4-Band Resistor
Problem:
A resistor has bands: Brown, Black, Red, Gold. What is its value?
Solution Steps:
- 11st band (Brown) = 1
- 22nd band (Black) = 0
- 33rd band (Red) = Multiplier ×100
- 44th band (Gold) = Tolerance ±5%
- 5Value = 10 × 100 = 1000Ω
- 6Express as: 1kΩ ±5%
Result:
1kΩ ±5% (actual value between 950Ω and 1050Ω)
Read a 5-Band Precision Resistor
Problem:
A resistor has bands: Yellow, Violet, Black, Brown, Brown. What is its value?
Solution Steps:
- 11st band (Yellow) = 4
- 22nd band (Violet) = 7
- 33rd band (Black) = 0
- 44th band (Brown) = Multiplier ×10
- 55th band (Brown) = Tolerance ±1%
- 6Value = 470 × 10 = 4700Ω = 4.7kΩ
Result:
4.7kΩ ±1% (precision resistor)
Create a Non-Standard Value
Problem:
You need 7.5kΩ but only have E12 series resistors. How can you make it?
Solution Steps:
- 1Target: 7500Ω
- 2Option 1: 15kΩ and 15kΩ in parallel = 7.5kΩ exactly
- 3Option 2: 6.8kΩ + 680Ω in series = 7.48kΩ
- 4Option 3: 10kΩ and 33kΩ in parallel
- 5Calculate: (10000 × 33000) / (10000 + 33000) = 7674Ω
- 6Closest single E12 value: 6.8kΩ or 8.2kΩ
Result:
Use two 15kΩ resistors in parallel for exactly 7.5kΩ
Tips & Best Practices
- ✓Use the mnemonic 'Bad Boys Race Our Young Girls But Violet Generally Wins' for colors 0-9.
- ✓Gold and silver are never first bands—they only appear as multiplier (÷10, ÷100) or tolerance.
- ✓When in doubt, verify with a multimeter—color codes can be misread, especially with faded or non-standard colors.
- ✓For circuits where exact values matter, use 1% (brown tolerance band) or better resistors.
- ✓E12 series values: 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 (memorize these!).
- ✓SMD code '0' means 0Ω jumper; 'R' in the code marks the decimal point position.
- ✓Two equal resistors in parallel = half the resistance but double the power handling.
Frequently Asked Questions
Sources & References
Last updated: 2026-01-22
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Editorial Note
MyCalcBuddy Editorial Team
This page is maintained as an educational calculator reference.
Formula Source: Standard Mathematical References
by Various