Calculate ohm values from resistor color codes, total resistance of parallel/series resistors, and conductor resistance based on size and conductivity.
The table provides numerical values for each color: digit values (0-9) for the 1st, 2nd, and 3rd bands; multiplier values (×0.01 to ×1G); tolerance percentages (±0.1% to ±20%); and Temperature Coefficient values (1 ppm/K to 250 ppm/K).
| Color | 1st, 2nd, 3rd Band | Multiplier | Tolerance | Temp Coefficient |
|---|---|---|---|---|
black | 0 | × 1 | — | 250 ppm/K (U) |
brown | 1 | × 10 | ±1% (F) | 100 ppm/K (S) |
red | 2 | × 100 | ±2% (G) | 50 ppm/K (R) |
orange | 3 | × 1,000 | ±0.05% (W) | 15 ppm/K (P) |
yellow | 4 | × 10,000 | ±0.02% (P) | 25 ppm/K (Q) |
green | 5 | × 100,000 | ±0.5% (D) | 20 ppm/K (Z) |
blue | 6 | × 1,000,000 | ±0.25% (C) | 10 ppm/K (Z) |
violet | 7 | × 10,000,000 | ±0.1% (B) | 5 ppm/K (M) |
grey | 8 | × 100,000,000 | ±0.01% (L) | 1 ppm/K (K) |
white | 9 | × 1,000,000,000 | — | — |
gold | — | × 0.1 | ±5% (J) | — |
silver | — | × 0.01 | ±10% (K) | — |
none | — | × 1 | ±20% (M) | — |
Think of a resistor like a traffic jam on a highway. Electricity wants to flow through a wire. But sometimes you need to slow it down. That's what a resistor does. It resists the flow of current.
The amount of resistance is measured in ohms (symbol: Ω). One ohm is a tiny amount. A thousand ohms is a kilohm (kΩ). A million ohms is a megohm (MΩ).
Resistors are too small to print numbers on them. So instead, they use colored bands. Each color stands for a number — it's like a secret code.
Color-to-Number Chart:
⚫ Black
0
🟤 Brown
1
🔴 Red
2
🟠 Orange
3
🟡 Yellow
4
🟢 Green
5
🔵 Blue
6
🟣 Violet
7
⚪ Gray
8
⬜ White
9
Here's a trick to remember: think rainbow order. ROYGBIV = Red, Orange, Yellow, Green, Blue, Violet = 2, 3, 4, 5, 6, 7. Add Black (0), Brown (1), Gray (8), White (9).
Most common resistors have 4 bands. Here's how they work:
Band 1
First digit
Band 2
Second digit
Band 3
Multiplier (zeros to add)
Band 4
Tolerance (±%)
📊 Example: Red, Red, Orange, Gold
These are more precise with an extra digit:
Band 1
First digit
Band 2
Second digit
Band 3
Third digit
Band 4
Multiplier
Band 5
Tolerance (±%)
📊 Example: Brown, Black, Black, Red, Brown
These are rare. They add a sixth band for temperature coefficient — how much the resistance changes with temperature. Most hobbyists never need this. It's for industrial or scientific applications where temperature stability is critical.
Reading bands in the wrong direction
Resistors don't have a 'right side up.' Look for the gap — the tolerance band (gold/silver) is usually separated from the others. Start reading from the opposite end.
Forgetting the multiplier
People see Red, Red, Red and think 222Ω. But it's actually 2,200Ω. The third band is a multiplier, not a digit.
Mixing up similar colors
Violet and Gray look similar in bad light. Blue and Green too. If unsure, use our calculator — it's more reliable than your eyes.
Connect end-to-end — they add up.
R_total = R₁ + R₂ + R₃ + ...
100Ω + 200Ω = 300Ω total
Side-by-side — total is less than the smallest.
1/R = 1/R₁ + 1/R₂ + 1/R₃ + ...
100Ω ∥ 200Ω = 66.67Ω total
See? Parallel resistance is lower than either resistor alone. That's why parallel circuits draw more current.
LEDs need a current-limiting resistor or they burn out instantly. With a 5V supply and LED needing 2V at 20mA: resistor = (5-2) ÷ 0.02 = 150Ω. Grab a 150Ω resistor and you're done.
Burnt resistor with faded colors? Use our calculator to try different color combinations until you find a standard value that makes sense for that circuit.
Need 5V from a 9V battery? Use two resistors to split the voltage. A 10kΩ and 8.2kΩ combination gives you exactly what you need.
Tolerance tells you how accurate the resistor is. A 100Ω resistor with ±5% tolerance could be anywhere from 95Ω to 105Ω. Fine for most hobby projects. For precision work, you need ±1% or even ±0.1%.
Use a multimeter to measure the resistance directly
Use our calculator and verify with a multimeter
Ask a friend to read the colors for you
Buy resistors with printed numbers (they exist!)
The color code system was invented in the 1920s by the Radio Manufacturers Association. Back then, resistors were huge. But as electronics got smaller, printing numbers became impossible. So colors it was.
The system is so good that it's still used today — over 100 years later. That's pretty impressive for a coding system.
Using our calculator is simple. Just select the number of bands (4, 5, or 6). Then click on the colors for each band. The calculator instantly shows you the resistance value.
You can also enter a resistance value and it will tell you the color code. That's useful when you're designing a circuit and need to find the right resistor. Try it now — it's free and works on your phone too.
An electronic color code specifies ratings of electrical components. For resistors, the first two/three bands are significant digits, the next is the multiplier, followed by tolerance. A 6th band may indicate temperature coefficient.
Example (5-band): Green=5, Red=2, Blue=6 → digits "526" × Gold (0.1) = 52.6 Ω with Brown tolerance ±1%
1/R = 1/R₁ + 1/R₂ + ... + 1/Rₙ
R = R₁ + R₂ + ... + Rₙ
R = L / (A × C)
Look for the gap. The tolerance band (usually gold or silver) is separated from the other bands. Start reading from the opposite end. If all bands are evenly spaced, the first band is usually closer to the edge.
The gold band is the tolerance. It means the resistor is accurate to within ±5% of its stated value. So a 100 ohm resistor with a gold band could be anywhere from 95 to 105 ohms.
A 4-band resistor has two digits, a multiplier, and a tolerance band. A 5-band resistor has three digits, a multiplier, and a tolerance band. The extra digit gives you more precision for exact values.
Just add them up. R_total = R₁ + R₂ + R₃ + ... For example, a 100Ω and 200Ω resistor in series give you 300Ω total.
Use 1/R_total = 1/R₁ + 1/R₂ + 1/R₃ + ... then take the reciprocal. A 100Ω and 200Ω in parallel = about 66.67Ω total.
A 6-band resistor adds a temperature coefficient band. It tells you how much the resistance changes with temperature. Most hobbyists never need this — it's for industrial or scientific applications.
Your circuit might not work correctly. Too much resistance and your LED might be dim. Too little resistance and components could overheat or burn out. Always double-check with a calculator or multimeter.
No. SMD (surface mount) resistors use a different numbering system with numbers printed on them, not colors. Our calculator is for through-hole resistors with color bands only.
Use a multimeter to measure the resistance directly. Or ask someone to read the colors for you. Some resistors also have the value printed on them. You can also buy resistors with printed numbers.
Tolerance tells you how much the actual resistance can vary from the stated value. A 100Ω resistor with ±5% tolerance could be 95-105Ω. For most circuits that's fine. For precision work, use ±1% or better.
Too much current is flowing through it. Check if you're using the right resistor value for your circuit. Also check the power rating — a small resistor might overheat if it's handling more than 1/4 watt.
Use the mnemonic: "Bad Boys Race Our Young Girls But Violet Generally Wins" = Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Gray, White. Or just use our calculator!
It's a resistor with a single black band. It has zero resistance and is used as a jumper wire on circuit boards. It's cheaper than using a wire in automated manufacturing.
Yes. Use series to add resistance or parallel to reduce it. You can create almost any value by combining standard resistors. Our calculator can help you find the right combination.