The standard 1 ohm colour code for a 4-band resistor is Brown, Black, Gold, Gold. For a 5-band precision resistor, the sequence is Brown, Black, Black, Silver, Brown. Because 1Ω is a very low resistance, the multiplier band drops to Gold (×0.1) or Silver (×0.01), which is where most reading errors happen on the bench.
The 1 Ohm Resistor Color Code Reference Table
Resistor colour codes are globally standardized under IEC 60062. Unlike wiring standards, there are no regional variations for component bands. Below is the exact breakdown for the two most common 1Ω resistor formats you will encounter in power supplies, current-sense circuits, and audio crossovers.
| Band Position | 4-Band (1Ω ±5%) | 5-Band (1Ω ±1%) | Numeric Value / Meaning |
|---|---|---|---|
| Band 1 (Digit 1) | Brown | Brown | 1 |
| Band 2 (Digit 2) | Black | Black | 0 |
| Band 3 (Digit 3) | N/A | Black | 0 (5-band only) |
| Multiplier | Gold | Silver | ×0.1 (4-band) / ×0.01 (5-band) |
| Tolerance | Gold (±5%) | Brown (±1%) | Acceptable deviation range |
| Calculation | 10 × 0.1 = 1.0Ω | 100 × 0.01 = 1.0Ω | Final Resistance | |
Standard Variants: IEC Resistor Codes vs. NEC/IEC Wire Colors
A common point of confusion for DIYers searching for a 'colour code' is mixing up component identification with mains wiring identification. If you are looking for the '1 ohm wire colour code', that is a category error: wire colours denote voltage, phase, and grounding, not resistance. However, because search intents frequently cross wires, here is the regional breakdown for mains wiring standards to ensure you do not apply component logic to a breaker panel.
| Function | IEC 60446 (EU/UK/AU - Harmonized) | NEC Article 200/210 (US/Canada) | Old UK (Pre-2004) |
|---|---|---|---|
| Live / Hot (Single Phase) | Brown | Black (or Red for 2nd hot) | Red |
| Neutral | Blue | White (or Grey) | Black |
| Earth / Ground | Green/Yellow Stripe | Bare, Green, or Green/Yellow | Green |
Rows People Get Wrong & Faded Marking Protocols
When you are troubleshooting a blown power supply or building a low-side current shunt, misreading a 1Ω resistor can lead to catastrophic overcurrent. Here are the specific bands that cause field failures and how to handle them.
The Multiplier Band: Gold vs. Silver
The most frequent bench mistake is misidentifying the multiplier on a 5-band resistor. A 4-band 1Ω resistor uses a Gold multiplier (×0.1). A 5-band 1Ω resistor uses a Silver multiplier (×0.01). Under harsh fluorescent lighting or when coated in conformal coating, Silver looks nearly identical to Gold. If you read a 5-band Silver multiplier as Gold, you will calculate the resistor as 10Ω instead of 1Ω, completely invalidating your current-sense math.
Brown vs. Red in the First Digit
Carbon film resistors baked by years of heat in a power supply often shift in hue. A Red first band (2) can easily look like Brown (1) when the epoxy body is scorched. If the first band is Red, the 4-band code is Red-Black-Gold-Gold, which is 2.0Ω, not 1.0Ω.
Safe Interpretation of Faded or Missing Markings
When the paint is entirely gone or the resistor is burnt to a crisp, do not guess. Use this protocol:
- De-energize and Isolate: Remove power. Discharge all filter capacitors. Desolder at least one leg of the resistor from the PCB to prevent parallel circuit paths from skewing your reading.
- Zero Your Meter: Touch your multimeter probes together. A standard test lead set will read between 0.1Ω and 0.3Ω. If your meter has a 'REL' (Relative) button, press it to zero out the lead resistance. If not, note the shorted value and subtract it manually.
- Measure and Verify: A healthy 1Ω resistor should read between 0.95Ω and 1.05Ω (for a 5% tolerance part). If it reads open (OL) or significantly higher (e.g., 4.7Ω), the carbon track has fractured from thermal stress and the part must be replaced.
Frequently Asked Questions
What is the exact 1 ohm colour code for a 5-band precision resistor?
The exact sequence is Brown, Black, Black, Silver, Brown. This translates to 1 (Brown), 0 (Black), 0 (Black), multiplied by 0.01 (Silver), with a 1% tolerance (Brown). This yields exactly 1.00Ω. You will typically see this format in metal film resistors used for precision current sensing in bench power supplies and digital multimeters.
Can I use a standard 1/4W 1 ohm resistor as a current shunt?
Generally, no. The limiting factor is not the resistance, but the power dissipation. Using Ohm's law (P = I²R), passing just 0.5A through a 1Ω resistor generates 0.25W of heat, which is the absolute maximum limit for a standard 1/4W carbon or metal film resistor. At 1A, it will dissipate 1W and instantly burn up. For current shunts, you must use a dedicated 1Ω power resistor (usually rated for 2W, 3W, or 5W) or a dedicated milliohm shunt (e.g., 0.01Ω) paired with an op-amp or dedicated current-sense IC like the INA219.
Why does my multimeter read 1.4 ohms on a brand new 1 ohm resistor?
You are measuring the resistance of your multimeter's test leads and the contact resistance of the probes against the component legs. Standard copper test leads and internal fuse connections easily add 0.2Ω to 0.4Ω to a measurement. To get an accurate reading on low-value resistors (anything under 10Ω), you must short the probes together, note the baseline resistance (e.g., 0.3Ω), and subtract that from your final reading (1.4Ω - 0.3Ω = 1.1Ω). Alternatively, use the 'Relative' (REL) or 'Zero' function on your multimeter before measuring.
