The 150 ohm color code for a standard 4-band through-hole resistor is Brown, Green, Brown, Gold. For a precision 5-band resistor, the sequence is Brown, Green, Black, Black, Gold (or Brown for 1% tolerance). If you are working with surface-mount (SMD) components, the 3-digit marking is 151.
Because 150Ω is a base value in the E12 and E24 standard decade series, it is one of the most common resistors you will find in a bench kit, frequently used for 5V LED current limiting and I2C pull-up networks. Below is the exact breakdown of how to read, verify, and replace this component across different packaging standards.
The 150 Ohm Color Code Reference Table
The table below maps the physical bands to their numeric equivalents. Read the bands from left to right, keeping the tolerance band (usually Gold or Silver) on the far right.
| Band Position | 4-Band (5% Tol) | 5-Band (1% Tol) | Numeric Value | Function |
|---|---|---|---|---|
| 1st Band | Brown | Brown | 1 | 1st Significant Digit |
| 2nd Band | Green | Green | 5 | 2nd Significant Digit |
| 3rd Band | Brown | Black | 0 (5-band) / x10 (4-band) | 3rd Digit OR Multiplier |
| 4th Band | Gold | Black | x1 (5-band) / ±5% (4-band) | Multiplier OR Tolerance |
| 5th Band | N/A | Brown (or Gold) | ±1% (or ±5%) | Tolerance |
Math check (4-band): 1 (Brown) and 5 (Green) = 15. Multiplier is 10 (Brown). 15 × 10 = 150Ω. All About Circuits provides a deeper dive into the E-series math that dictates why 150 is a standard value while 140 or 160 are not.
Standard Variants: IEC 60062, MIL-SPEC, and Wiring Confusion
A frequent point of confusion for makers transitioning from household wiring to electronics is mixing up component color codes with mains wiring standards. Regional wiring codes—such as NEC (US: black/hot, white/neutral, green/ground), IEC 60446 (EU: brown/hot, blue/neutral, green-yellow/ground), and the Old UK standard (red/hot, black/neutral)—apply strictly to cables, conductors, and terminal blocks. They do not apply to resistors.
Resistor color codes are universally governed by IEC 60062. Whether you purchase a Vishay, Yageo, or Panasonic resistor, the IEC standard dictates the band colors. However, there are two specific variant standards you will encounter on the bench:
- MIL-PRF-55342 (Military Spec): Adds a 6th band to indicate the failure rate (reliability) per 1,000 hours. If your 5-band 150Ω resistor has a Yellow 6th band, it denotes a 0.001% failure rate. Brown=1%, Red=0.1%, Orange=0.01%.
- SMD EIAJ Markings: Surface mount resistors use a 3-digit or 4-digit code. For 150Ω, the 3-digit code is 151 (15 × 10¹). Do not confuse this with "150", which on an SMD resistor means 15Ω (15 × 10⁰).
Bands People Get Wrong (and Faded Marking Recovery)
Even experienced technicians misread resistors under poor lighting or when components have been thermally stressed. Here are the specific rows and bands that cause errors with the 150Ω value:
1. The Multiplier vs. 3rd Digit Trap
When reading a 5-band 150Ω resistor (Brown-Green-Black-Black-Brown), beginners often treat the 3rd band (Black/0) as a multiplier instead of a significant digit, or they misread the 4th band (Black/x1) as a digit. If you accidentally read it as a 4-band code, you might calculate 15 × 0 = 0Ω, or 150 × 10 = 1500Ω. Rule of thumb: If the 4th band is Black, it is a 5-band resistor, because Black is never used as a tolerance band.
2. Faded Green vs. Blue
Carbon film resistors placed in high-heat zones (like near a voltage regulator or in a snubber circuit) suffer from thermal fading. The Green (5) band can oxidize and shift toward Blue (6) or Grey (8). If you read a faded resistor as Brown-Blue-Brown (160Ω), you can immediately catch the error: 160 is not a standard E12 or E24 value. The resistor is almost certainly a faded 150Ω or a 180Ω (Grey).
3. Safe Interpretation of Destroyed Markings
If a resistor is burnt to the point where the bands are illegible, do not guess based on the schematic alone; the previous repair technician may have substituted a value.
Decision Path: Sourcing the Exact 150Ω Replacement
Use this decision tree to select the correct 150Ω replacement part based on your specific circuit requirements. Do not default to whatever is closest on the bench; wattage and tolerance matter.
| If Your Application Is... | Then Choose This Specification | Concrete Part Pick |
|---|---|---|
| Standard 5V LED current limiting (up to 20mA) | 1/4W, 5% tolerance, 4-Band Carbon or Metal Film | Brown-Green-Brown-Gold (e.g., Yageo CFR-25JR-52-150R) |
| ADC voltage divider or precision op-amp feedback | 1/4W or 1/8W, 1% tolerance, 5-Band Metal Film | Brown-Green-Black-Black-Brown (e.g., Vishay PR02000201500JR500) |
| I2C Pull-up on a 3.3V bus (ESP32/Raspberry Pi) | 0603 or 0805 SMD, 1% or 5%, 1/10W | SMD marked "151" (e.g., Panasonic ERJ-3EKF1510V) |
| High-current dummy load or power supply bleed | 1W to 2W, 5% tolerance, Metal Oxide or Wirewound | Physical size scales up; bands remain Brown-Green-Brown-Gold |
| Markings are completely burnt/missing | Desolder one leg, measure, replace with nearest E24 value | Default to 1/4W 5% Metal Film unless DMM reads >1W dissipation |
Final Default Recommendation: If you are prototyping on a breadboard and need a 150Ω resistor but only have 5% carbon film and 1% metal film in your kit, always pick the 1% metal film (5-band). The 1/4W metal film resistors are physically more robust against soldering heat, their leads are typically thicker and grip breadboard contacts better, and the tighter tolerance ensures your LED brightness or bias voltages remain consistent across multiple builds.
