You've probably been there — staring at a tiny cylindrical component with colored stripes, trying to figure out if that's a 4.7kΩ or a 47kΩ resistor. Maybe you're sorting through a parts bin, or maybe you're double-checking a BOM before sending a board to fab. Either way, reading resistor color codes is one of those skills that sticks with you through an entire engineering career.
Let's break it down so you can read any resistor confidently, whether it has 4 bands, 5 bands, or 6 bands.
The Color Code System
Every resistor color band maps to a number. Here's the full lookup table:
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | — |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1k | — |
| Yellow | 4 | ×10k | — |
| Green | 5 | ×100k | ±0.5% |
| Blue | 6 | ×1M | ±0.25% |
| Violet | 7 | ×10M | ±0.1% |
| Grey | 8 | — | ±0.05% |
| White | 9 | — | — |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
Memorization trick: "Bad Beer Rots Our Young Guts But Vodka Goes Well" gets you Black through White for digits 0-9. It's silly but it works — most engineers learned it in their first year and never forgot.
4-Band Resistors: The Workhorse
4-band resistors are the most common type you'll encounter in through-hole projects. Here's how the bands break down:
- Band 1 — First significant digit
- Band 2 — Second significant digit
- Band 3 — Multiplier
- Band 4 — Tolerance
Example: Brown-Black-Orange-Gold
Let's decode a resistor with bands Brown, Black, Orange, Gold:
- Brown = 1 (first digit)
- Black = 0 (second digit)
- Orange = ×1k (multiplier)
- Gold = ±5% (tolerance)
So we get 10 × 1,000 = 10,000Ω = 10kΩ ±5%.
This is probably the most common resistor value in all of electronics. You'll find 10kΩ pull-up and pull-down resistors on practically every board you design.
Example: Red-Red-Brown-Gold
- Red = 2
- Red = 2
- Brown = ×10
- Gold = ±5%
22 × 10 = 220Ω ±5%. Another classic — commonly used for LED current-limiting resistors with 5V supplies.
5-Band Resistors: Higher Precision
5-band resistors give you an extra significant digit, which means tighter tolerance and more precise values. These show up in precision circuits — op-amp feedback networks, voltage references, measurement dividers.
- Band 1 — First significant digit
- Band 2 — Second significant digit
- Band 3 — Third significant digit
- Band 4 — Multiplier
- Band 5 — Tolerance
Example: Brown-Black-Black-Red-Brown
- Brown = 1
- Black = 0
- Black = 0
- Red = ×100
- Brown = ±1%
100 × 100 = 10,000Ω = 10kΩ ±1%.
Wait, that's the same value as our 4-band example. The difference? The ±1% tolerance. In a precision voltage divider, that matters. A 10kΩ ±5% resistor could actually be anywhere from 9.5kΩ to 10.5kΩ. The ±1% part narrows that to 9.9kΩ–10.1kΩ.
Example: Yellow-Violet-Black-Orange-Brown
- Yellow = 4
- Violet = 7
- Black = 0
- Orange = ×1k
- Brown = ±1%
470 × 1,000 = 470kΩ ±1%.
6-Band Resistors: Adding Temperature Coefficient
6-band resistors add one more piece of information: the temperature coefficient (sometimes called tempco). This tells you how much the resistance drifts with temperature changes, expressed in ppm/°C (parts per million per degree Celsius).
- Bands 1-5 — Same as 5-band
- Band 6 — Temperature coefficient
| Color | Temp Coefficient (ppm/°C) |
|---|---|
| Brown | 100 |
| Red | 50 |
| Orange | 15 |
| Yellow | 25 |
| Blue | 10 |
| Violet | 5 |
Example: Orange-Orange-Black-Black-Brown-Red
- Orange = 3
- Orange = 3
- Black = 0
- Black = ×1
- Brown = ±1%
- Red = 50 ppm/°C
330 × 1 = 330Ω ±1%, 50 ppm/°C.
What does 50 ppm/°C actually mean in practice? If the temperature changes by 50°C (say, from 25°C to 75°C), the resistance changes by:
ΔR = 330Ω × 50 × 50 / 1,000,000 = 0.825Ω
So the resistor could shift from 330Ω to about 330.8Ω. For a precision circuit, that's information you need. For an LED current limiter, you'd never care.
Which Way Do I Read It?
This is the question that trips people up the most. Here are a few reliable tricks:
Look for the gap. On most resistors, the tolerance band (gold, silver, or a tight-spaced band on a precision resistor) is spaced slightly farther from the other bands. Read from the opposite end.
Find the tolerance band. Gold and silver are never used as significant digits — they only appear as multipliers or tolerance. If you see gold or silver, that's your tolerance band, and you read from the other side.
Check for impossible values. If reading it one way gives you a value like 2.2Ω and the other way gives you 680MΩ, the lower value is almost certainly correct (unless you're working on something exotic).
When in doubt, grab your multimeter. No shame in that — even experienced engineers verify with a measurement when the stakes matter.
Surface Mount Resistors: A Quick Note
SMD resistors don't use color codes. They use numeric codes printed on the body:
- 3-digit codes work like 4-band:
472= 47 × 100 = 4.7kΩ - 4-digit codes work like 5-band:
4702= 470 × 10 = 4.7kΩ - EIA-96 codes use a two-digit lookup plus a multiplier:
01C= 100 × 100 = 10kΩ
The EIA-96 system is less intuitive but more compact — important when you're printing on an 0402 or 0201 package.
Common Values You'll See Everywhere
The EIA E24 series defines the standard resistor values for ±5% tolerance resistors. Here are the values you'll run into constantly:
| Decade | Values |
|---|---|
| ×1 | 10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, 30 |
| ×10 | 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82, 91 |
| ×100+ | Same ratios, multiplied up |
If you're designing a circuit and need a non-standard value like 3.4kΩ, you'll have to combine resistors or move to a tighter tolerance series (E96 for ±1%, which gives you 96 values per decade instead of 24).
Practical Tips from the Bench
Keep a reference card. Print out a color code chart and tape it to your workbench. After a few months you won't need it anymore, but it's a lifesaver when you're tired and second-guessing yourself.
Sort your parts bin. If you're pulling resistors from a mixed bin, measure them before you solder. Color codes can be hard to distinguish on cheap parts — brown and red look awfully similar under bad lighting.
Don't trust old stock. Resistor bodies can discolor over time, especially if they've been exposed to heat or UV. A faded brown band can look black, turning your 10kΩ into 100kΩ.
Use 1% as default. The price difference between ±5% and ±1% resistors is negligible these days. Unless you're mass-producing millions of units where every cent counts, just design with 1% parts. You get better precision and 5-band codes that are easier to read.
Verify critical values. For precision analog circuits — ADC reference dividers, current-sense resistors, feedback networks — always measure the actual resistance with a good DMM before soldering. A single bad resistor can ruin your entire calibration chain.
Standards Reference
The resistor color code system is defined in IEC 60062:2016 ("Marking codes for resistors and capacitors"). The E-series preferred values come from IEC 60063:2015. If you need the official word on how any of this should be marked, those are the documents to look up.
The EIA-96 SMD marking system is defined in EIA standard EIA-96-1 and widely adopted across the industry.
When to Use Which Resistor Type
| Application | Type | Tolerance | Why |
|---|---|---|---|
| LED current limiting | 4-band carbon film | ±5% | Doesn't need precision |
| Pull-up/pull-down | 4-band or 5-band | ±5% or ±1% | Non-critical but ±1% is cheap |
| Op-amp feedback | 5-band metal film | ±1% | Precision matters |
| Voltage reference divider | 5-band or 6-band | ±0.1% to ±1% | Drift directly affects accuracy |
| Current sensing | 6-band metal foil | ±0.1% + low tempco | Temperature stability critical |
Reading Resistor Color Codes Quickly
Here's a mental shortcut that speeds things up:
- Identify the tolerance band (usually gold or silver, sometimes brown for 1%)
- Read from the opposite end
- Write down the digits, then apply the multiplier
- Double-check — does the value make sense for this circuit?
With practice, you'll read common values like 10kΩ (brown-black-orange) and 4.7kΩ (yellow-violet-red) at a glance.
Want to skip the mental math and decode resistor values instantly? Try the Resistor Color Code Calculator — select your band colors and get the value immediately. It handles 4-band, 5-band, and 6-band resistors, shows tolerance ranges, and even works backwards: type in a resistance value and it shows you the color bands. Bookmark it for your bench.