The color code for a standard 1 Megaohm (1MΩ) resistor is Brown, Black, Green, Gold for 4-band (5% tolerance) components, and Brown, Black, Black, Yellow, Brown for 5-band (1% tolerance) precision components.
Critical Clarification: If your search intended 1 milli-ohm (1mΩ), standard axial color-banded resistors do not exist for that value. A 1mΩ component is a current shunt (usually a bare metal strip or specialized SMD) used for high-current sensing, not a standard signal resistor. The guide below strictly covers the 1 Megaohm (1,000,000 Ω) value, which is the standard intent behind this search query.
1MΩ Resistor Color Code Reference Table
| Band Position | 4-Band (5% Tolerance) | 5-Band (1% Tolerance) | Function / Meaning |
|---|---|---|---|
| Band 1 | Brown (1) | Brown (1) | 1st Significant Digit |
| Band 2 | Black (0) | Black (0) | 2nd Significant Digit |
| Band 3 | N/A | Black (0) | 3rd Significant Digit |
| Multiplier | Green (×100,000) | Yellow (×10,000) | Multiplier (Power of 10) |
| Tolerance | Gold (±5%) | Brown (±1%) | Tolerance Rating |
Decoding the Bands: What Each Row Means in Practice
Reading a resistor is a straightforward left-to-right process, provided you know which end is the start. For a 4-band 1MΩ resistor, the first two bands (Brown, Black) give you the base digits 10. The third band (Green) is the multiplier. Green represents 105, or 100,000. Multiplying 10 by 100,000 gives you 1,000,000 ohms (1MΩ). The final Gold band indicates the manufacturer guarantees the actual resistance will fall within ±5% of that target (between 950kΩ and 1.05MΩ).
For 5-band precision resistors, you get an extra significant digit. The first three bands (Brown, Black, Black) give you 100. The multiplier band is Yellow (104, or 10,000). Multiplying 100 by 10,000 again yields 1,000,000 ohms. The final Brown band denotes a tighter ±1% tolerance (990kΩ to 1.01MΩ).
Global Standards vs. Regional Variants
A common point of confusion for beginners transitioning from home wiring to electronics is the assumption that component colors vary by region. Unlike mains wiring—where you must navigate NEC (US black/white/green), IEC 60446 (EU brown/blue/yellow-green), and old UK (red/black) color codes—resistor band colors do not have regional variants.
Resistor color codes are universally governed by the IEC 60062 standard. A Brown-Black-Green-Gold resistor means 1MΩ whether you buy it in Tokyo, Berlin, or Chicago.
However, there are application-specific standard variants you should recognize:
- Commercial (IEC 60062): The standard color bands detailed in the table above. Typically painted on a beige or blue cylindrical body.
- Military (MIL-PRF-22684 / MIL-SPEC): Older military-spec resistors sometimes used a different physical layout. Instead of a distinct tolerance band on the far right, the body color itself indicated tolerance (e.g., a brown body meant ±1%, while a black body meant ±20%), and the bands were bunched toward one end. You will mostly see these in surplus or vintage avionics gear.
- SMD Equivalent (EIA-96): If you are moving from through-hole to surface mount, a 1MΩ 0603 or 0805 SMD resistor won't have color bands. Instead, it will be printed with 105 (for 5% tolerance: 10 × 105) or 1004 (for 1% tolerance: 100 × 104).
The 'Rows People Get Wrong' Notes
Even experienced technicians misread high-value resistors on the bench. Here are the specific failure modes and edge cases for 1MΩ components:
1. The Green vs. Blue Multiplier Trap
Under poor bench lighting, the green multiplier band (×100,000) can easily be mistaken for blue (×1,000,000). If you read Brown-Black-Blue-Gold, you are looking at a 10MΩ resistor, not 1MΩ. Always verify high-value resistors with a multimeter before soldering them into a high-gain feedback loop, as a 10x error will completely alter your circuit's gain or timing constant.
2. Reading Direction on 5-Band Resistors
On a 4-band resistor, the Gold or Silver tolerance band is visually distinct and always sits on the far right, making orientation obvious. On a 5-band 1% resistor, the tolerance band is Brown. Because Brown is also a valid significant digit (1) and multiplier (×10), you can easily read the resistor backward. The fix: Look for a slightly wider gap between the multiplier band and the tolerance band. If the spacing is uniform, use your multimeter to verify. A backward read of Brown-Yellow-Black-Black-Brown yields 1.4MΩ, which is close enough to 1MΩ to cause subtle debugging headaches.
3. The Body Resistance Measurement Error
This is the most common mistake when verifying a 1MΩ resistor. Human skin has a resistance ranging from 10kΩ (sweaty) to 100kΩ (dry). If you hold the metal leads of a 1MΩ resistor with your bare fingers while probing it with a multimeter, your body acts as a parallel resistor. The meter will read the parallel equivalent, often dropping the display to ~900kΩ or lower, leading you to falsely reject a perfectly good component. Always use alligator clips, a breadboard, or a dedicated component tester socket when measuring values above 100kΩ.
Frequently Asked Questions
How do I read a 1M resistor colour code if the paint is faded or burnt?
If a resistor has overheated, the brown and red bands often bake into a uniform, unreadable dark gray or black. If the bands are destroyed, you cannot visually decode it. You must desolder at least one leg of the resistor from the PCB to isolate it from parallel circuit paths, then measure it with a digital multimeter (DMM). If the DMM reads 'OL' (Open Loop), the resistive element has fractured internally and the component is dead. If it measures near 1MΩ, you can reuse it, but replacing it with a fresh 1% metal film unit is recommended for long-term reliability.
What is the exact difference between a 1MΩ and 1mΩ resistor?
The capitalization of the 'M' dictates a factor of one billion. 1MΩ (Megaohm) is 1,000,000 ohms, used for pull-up/pull-down networks, high-impedance op-amp feedback, and RC timing circuits. 1mΩ (milli-ohm) is 0.001 ohms, used almost exclusively as a current shunt to measure high amperage (e.g., measuring 50A across a 1mΩ shunt yields a 50mV drop). You will never find a 1mΩ axial component with standard IEC 60062 color bands; they are manufactured as thick metal strips, specialized SMD packages, or bare wire elements.
Why does my multimeter read 0.98 MΩ instead of exactly 1MΩ?
A reading of 0.98 MΩ (980,000 ohms) is perfectly normal and within spec. If you are using a standard 5% (Gold band) 1MΩ resistor, the acceptable factory tolerance range is 950kΩ to 1.05MΩ. Even if you are using a 1% (Brown band) precision resistor, the acceptable range is 990kΩ to 1.01MΩ. Furthermore, budget multimeters often have a basic DC accuracy of ±0.5% to ±1% on the Megaohm range. The combination of the resistor's manufacturing tolerance and your meter's internal accuracy easily accounts for a 2% deviation on the display.
Can I substitute a 1.2MΩ resistor if I don't have a 1MΩ on hand?
It depends entirely on the circuit function. In a digital logic pull-up resistor (e.g., on an I2C bus or a microcontroller GPIO pin), substituting 1.2MΩ for 1MΩ is usually fine, though it will slightly slow down the rise time of the signal edge. However, in an analog RC timing circuit (like a 555 timer astable mult oscillator) or an active op-amp filter, a 20% increase in resistance will directly cause a 20% shift in your cutoff frequency or oscillation period. In precision analog paths, never substitute values outside the specified tolerance band.
