A standard 4-band 100k (100,000 ohm) resistor uses the colour code Brown, Black, Yellow, Gold. A precision 5-band 100k resistor uses Brown, Black, Black, Orange, Brown. Unlike home wiring, where regional codes like the US NEC and European IEC 60446 dictate vastly different wire colours, resistor colour codes are universally standardized under IEC 60062. Below is the immediate breakdown for 100k ohm resistors, followed by the complete reference table and practical bench tips for reading faded components.
The 100k Resistor Colour Code: 4-Band vs 5-Band Breakdown
Resistors are manufactured in different precision tiers. A standard carbon or metal film resistor used for pull-ups and basic current limiting typically has 4 bands. Precision metal film resistors (1% or better tolerance) used in analog front-ends and voltage dividers use 5 or 6 bands. Here is exactly how the 100k value maps to each format.
| Format | Band 1 (Digit 1) | Band 2 (Digit 2) | Band 3 (Digit 3 / Multiplier) | Band 4 (Multiplier / Tolerance) | Band 5 (Tolerance / Tempco) | Typical Use Case |
|---|---|---|---|---|---|---|
| 4-Band (±5%) | Brown (1) | Black (0) | Yellow (×10,000) | Gold (±5%) | N/A | I2C pull-ups, LED limits, general prototyping |
| 5-Band (±1%) | Brown (1) | Black (0) | Black (0) | Orange (×1,000) | Brown (±1%) | Op-amp feedback, precision voltage dividers |
| 6-Band (±1%) | Brown (1) | Black (0) | Black (0) | Orange (×1,000) | Brown (±1%) + Red (50ppm/°C) | High-stability analog sensor circuits |
What each row means in practice: In the 4-band format, the first two bands form the base number (10), and the third band is the multiplier (104), yielding 10 × 10,000 = 100,000Ω. In the 5-band format, the first three bands form the base number (100), and the fourth band is the multiplier (103), yielding 100 × 1,000 = 100,000Ω. The final band always indicates the manufacturing tolerance.
Complete IEC 60062 Reference Table & Standard Variants
While electrical wiring colours fracture across borders (e.g., US NEC black/red/white vs. IEC 60446 brown/black/grey vs. old UK BS 7671 red/yellow/blue), electronic component marking is highly unified. The global standard is IEC 60062. However, if you are salvaging older equipment or buying military surplus, you may encounter legacy variants.
| Colour | Digit Value | Multiplier | Tolerance (4-Band) | Tolerance (5/6-Band) |
|---|---|---|---|---|
| Black | 0 | ×1 (100) | — | ±1% (Note: Brown is standard 1%) |
| Brown | 1 | ×10 (101) | ±1% | ±1% |
| Red | 2 | ×100 (102) | ±2% | ±2% |
| Orange | 3 | ×1,000 (103) | — | ±0.05% |
| Yellow | 4 | ×10,000 (104) | — | ±0.02% |
| Green | 5 | ×100,000 (105) | ±0.5% | ±0.5% |
| Blue | 6 | ×1,000,000 (106) | ±0.25% | ±0.25% |
| Violet | 7 | ×10,000,000 (107) | ±0.1% | ±0.1% |
| Grey | 8 | ×100,000,000 (108) | ±0.05% | ±0.01% |
| White | 9 | ×1,000,000,000 (109) | — | — |
| Gold | — | ×0.1 (10-1) | ±5% | — |
| Silver | — | ×0.01 (10-2) | ±10% | — |
Standard Variants to Watch For:
- IEC 60062 (Global/Commercial): The current universal standard. If you buy a Vishay or Bourns resistor today, it follows this exact chart.
- EIA/RS-279 (Legacy US): The older Electronic Industries Alliance standard. The colour mappings are identical to IEC 60062, but older documentation may use different tolerance letter suffixes printed on the body alongside the bands.
- MIL-PRF-55342 (US Military): Military-spec surface mount and leaded resistors often abandon colour bands entirely in favour of 3-digit or 4-digit stamped alphanumeric codes (e.g., "104" for 100k) to survive harsh conformal coating and solvent washes. Do not confuse a 3-band military resistor with a standard commercial 3-band resistor.
Rows People Get Wrong & Faded Band Recovery
Even experienced engineers misread resistors under poor bench lighting or when dealing with aged components. Here are the most common pitfalls and how to resolve them.
1. The Multiplier Confusion (Yellow vs. Orange)
This is the #1 cause of reading a 100k resistor as a 10k resistor. On many cheap carbon film resistors, the yellow multiplier band is printed with a slightly greenish or brownish tint, making it look orange. Rule of thumb: If the resistor is 4-band and the third band is distinctly reddish, it is Orange (10k). If it looks like mustard or pale brown, it is Yellow (100k). Always verify the tolerance band spacing to ensure you are reading left-to-right.
2. Reading Direction (Where is the Tolerance Band?)
The tolerance band (usually Gold or Silver for 4-band, Brown or Red for 5-band) is often separated from the value bands by a slightly wider gap. Furthermore, Gold and Silver never appear as the first digit band. If you see Gold on the far left, you are holding the resistor backwards.
3. Safe Interpretation of Faded Markings
Older carbon composition and early carbon film resistors degrade under thermal stress. Red bands frequently fade to a pale orange, and yellow bands can bleach out to look like faded green or white. If you are salvaging parts from a 1980s audio amplifier and the bands are ambiguous:
Safe Interpretation and Multimeter Verification
The only way to safely interpret a questionable 100k resistor colour code is to verify it with a digital multimeter (DMM). However, how you measure it matters just as much as the colour code itself.
Expected Measurement Ranges:
A 100k resistor with a Gold (±5%) tolerance band should measure between 95,000Ω and 105,000Ω. A 100k resistor with a Brown (±1%) tolerance band should measure between 99,000Ω and 101,000Ω. If your DMM reads 112kΩ on a 5% resistor, the component has drifted due to thermal aging or moisture ingress and should be discarded.
The In-Circuit Measurement Trap:
If you probe a 100k resistor while it is still soldered into a PCB, you are not measuring the resistor alone; you are measuring the resistor in parallel with the rest of the circuit. Because parallel resistance always results in a value lower than the smallest individual resistor, an in-circuit 100k resistor might read as 45kΩ if there is a parallel IC input or another trace path. Always lift one leg of the resistor out of the PCB pad before measuring to isolate it from parallel circuit paths.
By combining the IEC 60062 table with proper DMM isolation techniques, you can confidently identify, verify, and deploy 100k resistors in any prototype or repair scenario without relying on guesswork.
