The color code for a standard 150 ohm resistor with a 5% tolerance is Brown, Green, Brown, Gold. If you are using a precision 1% tolerance resistor (5-band), the sequence is Brown, Green, Black, Black, Brown.
Unlike mains wiring, where you must navigate NEC vs. IEC vs. old UK regional color codes, through-hole resistor banding is globally harmonized. However, interpreting the bands correctly requires understanding the multiplier mechanics, recognizing legacy military variants, and knowing how to verify components when heat has destroyed the paint. Below is the complete reference data for the 150Ω value.
Decoding the 150 Ohm Resistor Color Code (Reference Tables)
The global baseline for resistor color coding is IEC 60062. This standard dictates that the bands are read from left to right, ending with a physically separated tolerance band on the right. For a 150 ohm value, the mathematical breakdown relies on combining the significant digits (1 and 5) with the correct decimal multiplier.
4-Band Standard (5% Tolerance)
The 4-band format is the most common for general-purpose carbon and metal film resistors (like the classic Vishay PR02 or Yageo CFR-25 series). It uses two significant digits and one multiplier.
| Band Position | Color | Function | Numeric Value |
|---|---|---|---|
| Band 1 (Left) | Brown | 1st Significant Digit | 1 |
| Band 2 | Green | 2nd Significant Digit | 5 |
| Band 3 | Brown | Multiplier | ×10 (10¹) |
| Band 4 (Right) | Gold | Tolerance | ±5% |
Calculation: 15 × 10 = 150Ω.
5-Band Precision (1% Tolerance)
For metal film precision resistors (common in op-amp feedback loops and ADC voltage dividers), a third significant digit is added. Because 150 is a clean three-digit number, the third digit is zero.
| Band Position | Color | Function | Numeric Value |
|---|---|---|---|
| Band 1 (Left) | Brown | 1st Significant Digit | 1 |
| Band 2 | Green | 2nd Significant Digit | 5 |
| Band 3 | Black | 3rd Significant Digit | 0 |
| Band 4 | Black | Multiplier | ×1 (10⁰) |
| Band 5 (Right) | Brown | Tolerance | ±1% |
Calculation: 150 × 1 = 150Ω.
Standard Variants: MIL-SPEC, SMD, and EIA-96 Equivalents
While IEC 60062 governs modern commercial through-hole resistors, you will encounter different marking standards depending on the era and package type of your component.
Legacy US MIL-PRF-22684 (Military Spec)
If you are repairing vintage US military or aerospace equipment, you may find a 5-band or 6-band resistor where the final band does not indicate tolerance. Under the older MIL-PRF-22684 standard, the first four bands represent the value (identical to the 4-band IEC table above), but the 5th band indicates reliability (failure rate) per 1,000 hours of operation.
- Yellow 5th Band: 0.1% failure rate (Mil-spec 150Ω)
- Red 5th Band: 0.01% failure rate
- Brown 5th Band: 1.0% failure rate
Note: Tolerance on these older MIL-spec parts was often assumed to be ±5% unless otherwise stamped on the packaging.
SMD (Surface Mount) Equivalents
When transitioning from through-hole to SMD footprints (like 0805 or 0603 packages), color bands are replaced by printed numeric codes. For a 150 ohm SMD resistor, look for these markings:
- 3-Digit Code (5%):
151(15 × 10¹ = 150Ω) - 4-Digit Code (1%):
1500(150 × 10⁰ = 150Ω) - EIA-96 Code (1%):
18A(18 is the lookup code for 150; A is the multiplier for ×1)
A 3-digit SMD code of
151 means 150 ohms. However, a code of 000 or a simple black band across an SMD package indicates a 0Ω jumper, not a shorted 150Ω resistor. Always verify SMD values with a micro-probe DMM if the silkscreen is ambiguous.
Bands People Get Wrong and Reading Faded Components
Even experienced bench technicians misread resistors. The errors rarely stem from not knowing the color chart; they stem from environmental factors, manufacturing variances, and thermal degradation.
The 'Rows' (Bands) People Get Wrong
- Red vs. Brown in Warm Lighting: Under standard 2700K warm-white bench lighting, the red band (digit 2) and brown band (digit 1) look nearly identical. A 150Ω resistor (Brown-Green) misread as Red-Green becomes a 250Ω resistor. Fix: Always inspect color codes under a 5000K daylight-balanced LED task lamp or near a north-facing window.
- The Multiplier Trap (Brown as ×10 vs. Digit 1): In the 4-band 150Ω sequence, the third band is Brown. Novices often see Brown and instinctively write down '1', resulting in a calculation of 151Ω instead of 15 × 10. Remember: the third band in a 4-band system is always a multiplier (number of zeros), never a standalone digit.
- Reading Backwards: If your sequence appears to be Gold-Brown-Green-Brown, you are holding the component backward. Gold and Silver are exclusively used for tolerance (±5% and ±10%) and are never used as significant digits or multipliers. They physically sit slightly separated from the main cluster of bands.
Safe Interpretation When Markings are Faded or Burned
Resistors in power supplies, LED drivers, and linear voltage regulators often overheat. A 150Ω current-limiting resistor that has cooked at 150°C for a few thousand hours will experience paint darkening, turning the green band black and the brown bands indistinguishable.
When visual identification fails, you must measure the resistance. However, never measure a resistor while it is fully soldered into a live or unpowered circuit.
If you place your multimeter probes across a 150Ω resistor still soldered to a PCB, you are measuring the entire parallel network connected to those traces. A 150Ω resistor in parallel with a 300Ω IC pull-up network will read exactly 100Ω on your DMM, leading you to falsely conclude the resistor has drifted or failed.
The Correct Verification Procedure:
- De-energize the circuit and discharge all bulk capacitors.
- Use a soldering iron to lift one leg of the resistor completely out of the PCB pad.
- Measure across the lifted component. A healthy 150Ω 5% resistor will read between 142.5Ω and 157.5Ω.
- If the reading is wildly off (e.g., 400Ω or OL/Open), the carbon track has fractured internally due to thermal stress, and the component must be replaced.
For a comprehensive cross-reference of standard E12/E24 values and further testing methodologies, the All About Circuits resistor reference guide remains an excellent bench companion alongside your DMM.
