Resistor Color Code Calculator
Decode resistor color bands to find resistance and tolerance, or enter a resistance value to see the corresponding color bands.
Reviewed by the ToolNestr Editorial Team — July 2026
| Color | Digit | Multiplier | Tolerance | TCR (ppm/K) |
|---|---|---|---|---|
| Black | 0 | \u00d71 Ω | — | — |
| Brown | 1 | \u00d710 Ω | ±1% | 100 ppm/K |
| Red | 2 | \u00d7100 Ω | ±2% | 50 ppm/K |
| Orange | 3 | \u00d71000 Ω | — | 15 ppm/K |
| Yellow | 4 | \u00d710000 Ω | — | 25 ppm/K |
| Green | 5 | \u00d7100000 Ω | ±0.5% | 20 ppm/K |
| Blue | 6 | \u00d71000000 Ω | ±0.25% | 10 ppm/K |
| Violet | 7 | \u00d710000000 Ω | ±0.10% | 5 ppm/K |
| Grey | 8 | \u00d7100000000 Ω | ±0.05% | 1 ppm/K |
| White | 9 | \u00d71000000000 Ω | — | — |
| Gold | — | \u00d70.1 | ±5% | — |
| Silver | — | \u00d70.01 | ±10% | — |
Worked example
Red-Violet-Orange-Gold (4-band)
Brown-Black-Red-Silver (4-band)
Identifying Unknown Resistors
When you find an unmarked or loose resistor in your parts bin, match its colour bands against the calculator to determine its resistance value, tolerance, and temperature coefficient instantly.
Electronics Repair
During troubleshooting, quickly verify that a resistor matches its schematic value. A shifted colour band can indicate heat damage or a factory error that causes circuit malfunction.
Education and Learning
Students learning electronics can practice reading resistor colour codes, check their manual calculations, and build confidence before working with real components in lab sessions.
BOM Verification
When receiving a batch of resistors, spot-check the colour codes against the bill of materials to ensure the correct values were shipped before populating printed circuit boards.
Tips for reading resistor colour codes
Gold and silver indicate the right side
The tolerance band is usually gold (±5%) or silver (±10%) and is separated from the other bands by a slightly larger gap. Orient the resistor so this band is on the right, then read left to right.
Use the mnemonic
Bad Boys Run Over Yellow Grass But Violet Grey Wins. Each word’s first letter matches a colour: Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey, White. This makes memorising the 0–9 digit mapping easy.
Check with a multimeter
When colours are faded or the resistor is very small, measure with a multimeter to confirm. The measured value should fall within the tolerance range of the colour-coded value.
Watch for common confusions
Red and orange can look similar in dim light. Violet and blue are also easily confused. Use bright, white lighting or a magnifying lamp to distinguish bands accurately, especially on 5- and 6-band resistors.
Black as a multiplier means ×1
A black multiplier band means multiply by 1, not by 0. For example, Brown-Black-Black-Gold = 10 × 1 = 10 Ω at ±5%. This is a very common mistake beginners make.
How resistor colour codes work
Resistor colour coding was standardised in the early 20th century as a practical way to mark resistance values on small cylindrical components where printing numbers would be illegible. The system is defined by the IEC 60062 international standard and is universally adopted for all through-hole resistors. Each colour corresponds to a specific digit from 0 to 9, with additional colour assignments for multiplier, tolerance, and temperature coefficient.
4-band vs 5-band vs 6-band resistors
4-band resistors are the most common general-purpose type. The first two bands are significant digits, the third band is the decimal multiplier, and the fourth band is the tolerance. A typical 4-band resistor might be Brown-Black-Red-Gold = 1,000 Ω (1 kΩ) at ±5%. These are inexpensive and widely available in the E12 and E24 standard value series.
5-band resistors provide higher precision by adding a third significant digit. The first three bands are digits, the fourth is the multiplier, and the fifth is the tolerance. These are typically used in circuits where accuracy matters, such as voltage dividers, measurement equipment, and audio crossovers. A 5-band resistor might read Brown-Black-Black-Brown-Brown = 1,000 Ω at ±1%.
6-band resistors extend the 5-band format with a sixth band that indicates the Temperature Coefficient of Resistance (TCR) in parts per million per kelvin (ppm/K). This tells you how much the resistance changes with temperature, which is critical in precision instrumentation, automotive electronics, and aerospace applications where components experience wide temperature swings.
Reading order and orientation
Always read the resistor from the end closest to the first colour band. The tolerance band is typically separated from the digit and multiplier bands by a larger gap, making it easy to identify which end is the starting point. If the resistor has no visible gap (common on some older or small-bodied components), look for the gold or silver band — those colours only appear as tolerance or multiplier, never as digit bands, so they help you orient the resistor correctly.
When using the reverse mode of this calculator, you enter a resistance value and the tool finds the nearest standard resistor colour combination. This is useful when designing a circuit and you need to know which colour-coded part to order or pull from inventory.
Common mistakes
Reading the resistor backwards is the most frequent error — always place the tolerance band on the right. Confusing red and orange or violet and blue is common under poor lighting. Mistaking the black multiplier band (which means ×1, not ×0) can lead to values that are off by a factor of ten. Forgetting that gold and silver can be multipliers (0.1 and 0.01 respectively) as well as tolerance indicators is another pitfall.
Always verify your reading with a second pass or use the calculator’s visual band display to confirm each colour matches what you see on the physical component. When in doubt, measuring with a multimeter provides definitive confirmation.
Standard value series (E-series)
Resistor values are not arbitrary — they follow standardised decades called E-series. The E12 series (12 values per decade) includes: 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, and 82. The E24 series adds intermediate values: 11, 13, 16, 20, 24, 30, 36, 43, 51, 62, 75, and 91. Higher precision resistors use E48, E96, or even E192 series with correspondingly tighter tolerances. Using standard values ensures your designs use readily available, low-cost components.
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Frequently asked questions
How do I read a resistor?
Hold the resistor with the tolerance band (gold/silver) on the right, then read bands from left to right.
What is a 4-band resistor?
Two digit bands, one multiplier band, and one tolerance band.
What is a 5-band resistor?
Three digit bands for higher precision, one multiplier, one tolerance.
What does the 6th band mean?
The 6th band indicates the temperature coefficient in ppm/K.
What is the resistor color code mnemonic?
Bad Boys Run Over Yellow Grass But Violet Grey Wins — Black (0), Brown (1), Red (2), Orange (3), Yellow (4), Green (5), Blue (6), Violet (7), Grey (8), White (9).
What is the difference between 4, 5 and 6 band resistors?
4-band gives two significant digits, 5-band gives three significant digits for higher precision, and 6-band adds the temperature coefficient.
Can gold or silver be digit bands?
No — gold and silver only appear as multiplier or tolerance bands. Only black through white are used for digit values.
What is reverse mode?
Reverse mode lets you type a resistance value (e.g. 47000 or 4.7k) and the calculator shows the nearest standard color bands.
Sources & references
This tool uses standard formulas and reference values from:
- • NFPA 70 — National Electrical Code (NEC), conduit fill, box fill and conductor ampacity. nfpa.org
- • IPC-2221, Generic Standard on Printed Board Design (trace width / current). ipc.org
- • NIST reference constants and unit definitions; IEEE standards where applicable. nist.gov
For educational and preliminary use. Verify against full engineering calculations and the governing standard before any real design.