Resistor Color Code Guide & Calculator: How to Read 4, 5 and 6 Band Resistors

What a Resistor Is and Why Circuits Need Them

A resistor limits current and turns the excess electrical energy into heat. Current follows Ohm's law, I = V / R. Connect an LED (forward voltage about 2.0 V) straight to a 12 V supply and nothing limits the current except the supply itself, so the LED is destroyed almost instantly. Put a 470 Ω resistor in series and it takes up the remaining 10 V: I = 10 V ÷ 470 Ω ≈ 21 mA, which a typical LED handles comfortably.

Resistance is measured in ohms (Ω). 1 kΩ is 1,000 Ω and 1 MΩ is 1,000,000 Ω. If it helps, picture water in a pipe: voltage is the pressure, current is the flow, and resistance is a narrow section that restricts it. Reading a value wrong has real consequences. Fit 4.7 kΩ where 470 Ω was intended and ten times less current flows, so an LED comes out dim, or a transistor that needed base current never switches fully on.

Why Resistors Use Color Bands Instead of Printed Numbers

Surface-mount parts lie flat on a board with their markings facing up. Axial through-hole resistors are little cylinders instead, and once soldered in they can end up at any rotation. A printed number such as "4700" could easily face down toward the board, and you would have to desolder the part to read it.

Bands wrap all the way around the body, so some of every band is visible from above whichever way the part sits. They are also easier to apply than text. A typical 1/8 W or 1/4 W resistor is only about 3 to 7 mm long, and tiny printed digits on a curved, warm coating can smudge, rub off or discolor. Solid paint bands survive handling and heat much better.

The IEC 60062 Resistor Color Code Chart

The color code for fixed resistors is defined in IEC 60062 (the older US standard, EIA RS-279, uses the same colors). Each color stands for a digit from 0 to 9, a multiplier, a tolerance and, on precision parts, a temperature coefficient (TCR). The chart below lists them all:

*Tolerance letters in brackets are the IEC letter codes. Colors that mean a very tight tolerance (Orange, Yellow, Grey) are rare in practice, and TCR figures can differ between manufacturers, so check the datasheet for any precision design.

How to Read a 4-Band Resistor (Step by Step)

The 4-band resistor is the classic through-hole part you find in kits, consumer gear and older power supplies. It carries two digits, a multiplier and a tolerance:

1. Band 1 (first digit): the band nearest one end gives the tens digit.
2. Band 2 (second digit): the next band gives the units digit, so the two together make a number from 10 to 99.
3. Band 3 (multiplier): the power of ten to multiply by. Gold means ×0.1 (divide by 10) and silver means ×0.01 (divide by 100).
4. Band 4 (tolerance): set apart by a slightly wider gap. Gold (±5%) is by far the most common on ordinary carbon film parts.

How to Read a 5-Band Resistor (Precision Metal Film)

Five-band resistors are usually 1% (or tighter) metal film parts, often with a blue body. The E24 values from a 4-band part are too coarse for precision work such as filters, dividers or ADC reference networks, so these carry three digits before the multiplier:

1. Band 1: first digit (hundreds).
2. Band 2: second digit (tens).
3. Band 3: third digit (units), so the three make a number from 100 to 999.
4. Band 4 (multiplier): the power of ten.
5. Band 5 (tolerance): Brown = ±1%, Red = ±2%, Green = ±0.5%, Blue = ±0.25%, Violet = ±0.1%.

6-Band Resistors & Temperature Coefficient (TCR)

A 6-band resistor is a 5-band resistor with one extra band at the end for the temperature coefficient of resistance (TCR). TCR is given in parts per million per kelvin (ppm/K, the same as ppm/°C for a change in temperature) and tells you how much the value drifts as the part gets warmer or cooler.

Take a 10 kΩ resistor with a Brown 6th band (100 ppm/K) in an enclosure that warms from 25 °C to 75 °C, a rise of 50 °C. The drift is 10,000 Ω × (100 ÷ 1,000,000) × 50 = 50 Ω, or 0.5%. With a Blue band (10 ppm/K) it is only 5 Ω. That difference matters in precision dividers, references and sensor front-ends, and almost never in an LED or pull-up resistor.

Which End of the Resistor Do I Read First?

Reading from the wrong end is the most common slip. Yellow-Violet-Brown-Gold (470 Ω) read backwards starts with Gold, which cannot be a digit, and the result is nonsense. These checks usually settle it:

• Look for the gap: there is usually a wider space between the multiplier and the tolerance band. The bunched bands are the digits and multiplier. The band on its own is the tolerance.
• Check for Gold or Silver: they are never used as a digit. If one sits on an outer band, that end is the tolerance, so start from the other end.
• See which band is closer to a lead: on many small parts the bands are shifted toward one end. The band nearest a lead is normally Band 1.
• Compare with standard values: one direction might read 1-0-2-Gold (1 kΩ, a very common value) while the other starts with Gold and makes no sense. The sensible one wins.
• Still unsure, measure it: if the light is poor or the coating is discolored by heat, measure the resistor out of circuit with a multimeter. Once you know it reads about 4.7 kΩ, the bands are easy to match.

Original Memory Trick for the Color Sequence

Apart from the neutrals at each end (Black and Brown at the bottom, Grey and White at the top), the colors follow the order of the rainbow:

This original mnemonic follows the same first letters:

"Bright Bench Resistors Open Your Gateway: Build Vital Gadgets Wisely."

The tricky parts are Black versus Brown at the start, and Blue, Violet and Grey near the end. Black is 0 (nothing), Brown is the next step up at 1. Violet (7) sits between Blue (6) and Grey (8), and White (9) closes the list. For the tolerance bands, Gold (5%) beats Silver (10%) in precision, which is easy to remember because gold is the more valuable metal.

Writing Values Correctly: Engineering Prefixes and R/K/M Notation

On schematics and parts lists, large values are not written with strings of zeros. They use SI prefixes:

• Ohms (Ω): values below 1,000 Ω, such as 10 Ω, 330 Ω or 470 Ω.
• Kilohms (kΩ): 1 kΩ = 1,000 Ω, so 4,700 Ω is 4.7 kΩ and 10,000 Ω is 10 kΩ.
• Megohms (MΩ): 1 MΩ = 1,000,000 Ω, so 2,200,000 Ω is 2.2 MΩ and 10,000,000 Ω is 10 MΩ.

The R, K and M letter code (IEC 60062, BS 1852): Decimal points vanish easily on photocopies, small silkscreen and worn markings, and "4.7k" is easily misread as "47k". So the letter takes the place of the decimal point:

What Tolerance Really Means and the E-Series Preferred Values

No production process gives exactly the nominal value. Tolerance is the maximum allowed deviation from nominal (at 25 °C). For a 100 Ω resistor with ±5% tolerance (Gold band), the actual value can be anywhere between:

If your meter shows 98.4 Ω, the resistor is fine. It is inside the range.

Why there is no 500 Ω resistor: Catalogues list 470 Ω and 510 Ω but not 500 Ω, because values follow the preferred number series of IEC 60063, which are spaced evenly on a log scale. The E12 series (±10%) has 12 values per decade: 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82. Each step is wide enough to be worth making but close enough that ranges meet. For example 47 Ω +10% is 51.7 Ω and 56 Ω −10% is 50.4 Ω, so the two overlap. E24 (±5%) doubles the number of values, and the E96 series (96 per decade, used for 1% parts) includes values such as 475 Ω and 499 Ω.

Common Bench Mistakes When Reading Resistors

Colors can be deceptive, and a few mistakes come up again and again:

• Reading from the wrong end: look for the Gold or Silver band or the wider gap first. Without that check, a 5-band part such as Brown-Black-Black-Red-Brown (10 kΩ) read backwards gives Brown-Red-Black-Black-Brown, which is 120 × 1 = 120 Ω, a believable but wrong value.
• Poor lighting: under warm or dim light Red, Brown and Orange can look almost the same. Look at the part in daylight or under a bright neutral-white lamp.
• Mixing up Gold and Yellow: Yellow is a flat color and means the digit 4. Gold has a metallic sheen and means ×0.1 or ±5%. Gold is never a digit.
• Treating the multiplier as a digit: a Red third band means ×100 (two zeros), not a 2 tacked on the end. Brown-Black-Red is 1,000 Ω (1 kΩ), not 102 Ω.
• Expecting bands on every resistor: power wirewound resistors, chassis-mount parts and SMD chips usually have the value printed on them. If there is text, read the text.

Confirming Resistance with a Digital Multimeter (DMM)

A multimeter is the surest check, as long as you measure properly:

1. Take it out of the circuit: measure with the board unpowered (and any large capacitors discharged), and lift at least one leg of the resistor. Anything else connected across it, such as other resistors, diode junctions or capacitors, forms a parallel path, and parallel resistance is always lower than either branch: 1/R_eq = 1/R₁ + 1/R₂. A reading taken in circuit is usually too low.
2. Do not pinch both probes: on high values (100 kΩ and up), your skin resistance, which can be in the tens to hundreds of kilohms, ends up in parallel with the resistor and pulls the reading down. Hold the part by one lead only, or clip it.
3. Allow for the leads: test leads typically add a few tenths of an ohm. For anything under about 10 Ω, touch the probes together first, note the reading (or press REL/Null), and subtract it.

SMD Resistors in Brief: 3-Digit, 4-Digit, and EIA-96 Codes

SMD resistors (sizes such as 0805, 1206 and 2512) are flat ceramic chips with printed characters instead of bands. Many small ones, especially 0402 and smaller, carry no marking at all. The main schemes are:

• 3-digit code (usually 5% parts): the first two digits are the value and the third is the number of zeros.
  • 103 = 10 × 10³ = 10,000 Ω (10 kΩ)
  • 472 = 47 × 10² = 4,700 Ω (4.7 kΩ)
  • 330 = 33 × 10⁰ = 33 Ω (not 330 Ω!)
• R as the decimal point: for values below 10 Ω, the R marks where the decimal point goes.
  • 4R7 = 4.7 Ω
  • 0R22 = 0.22 Ω
  • 0R0 or 0 = 0 Ω (zero-ohm jumper link)
• 4-digit code (usually 1% parts): three digits for the value, then the number of zeros.
  • 1002 = 100 × 10² = 10,000 Ω (10 kΩ)
  • 4751 = 475 × 10¹ = 4,750 Ω (4.75 kΩ)
• EIA-96 code: small 1% chips (0603 and similar) use a two-digit code (01 to 96) that points to an E96 value, followed by a multiplier letter (Y = 0.01, X = 0.1, A = 1, B = 10, C = 100, D = 1,000). For example 01C is 100 × 100 = 10 kΩ.

Frequently Asked Questions About Resistor Color Codes

Key Takeaways for the Bench

• Start away from the gap: the tolerance band (often Gold ±5% or Brown ±1%) sits apart from the digits, and Gold or Silver is never the first band.
• 4-band = 2 digits + multiplier; 5-band = 3 digits + multiplier: the extra digit lets 1% metal film parts mark values like 4.75 kΩ.
• Gold and Silver as multipliers: Gold is ×0.1 and Silver is ×0.01, which is how values like 4.7 Ω are marked.
• Measure out of circuit: parallel paths make in-circuit readings misleading, so lift one lead first.

Sources and Standards

The color sequence, letter codes and preferred-value series on this page follow these published standards:

• IEC 60062: Marking codes for resistors and capacitors (Color code bands, letter and digit codes, temperature coefficients).
• IEC 60063: Preferred number series for resistors and capacitors (E6, E12, E24, E48, E96, E192 series).
• IEC 60115-1: Generic specification for fixed resistors for use in electronic equipment (Rated dissipation, thermal derating, environmental limits).
• EIA-RS-279 / MIL-STD-1285: Color code for identification of passive electronic components.

Standards are cited by title only. Check the edition that applies in your region or contract.