A 2k (2,000 ohm) resistor uses the color code Red-Black-Red for standard 4-band components, and Red-Black-Black-Brown for precision 5-band components. The tolerance band is typically Gold (±5%) or Brown (±1%). If you are holding a through-hole resistor and need to verify its value immediately, read the bands from left to right, stopping before the wider, separated tolerance band on the right.
The 2k Resistor Color Code: Direct Answer & Reference Table
Below is the complete IEC 60062 reference table. The top section breaks down the exact bands for a 2k resistor across 4-band, 5-band, and 6-band formats. The bottom section provides the universal color-to-digit mapping used to decode any resistor on your bench.
| Format | Band 1 (Digit) | Band 2 (Digit) | Band 3 (Digit/Mult) | Band 4 (Mult/Tol) | Band 5 (Tol) | Band 6 (Temp Co) |
|---|---|---|---|---|---|---|
| 4-Band (5%) | Red (2) | Black (0) | Red (×100) | Gold (±5%) | - | - |
| 5-Band (1%) | Red (2) | Black (0) | Black (0) | Brown (×10) | Brown (±1%) | - |
| 6-Band (1%) | Red (2) | Black (0) | Black (0) | Brown (×10) | Brown (±1%) | Red (100ppm) |
| Universal Color Code Reference (IEC 60062) | ||||||
| Color | Digit Value | Multiplier | Tolerance | Temperature Coefficient | ||
| Black | 0 | ×1 (10^0) | - | - | ||
| Brown | 1 | ×10 (10^1) | ±1% | 100 ppm/°C | ||
| Red | 2 | ×100 (10^2) | ±2% | 50 ppm/°C | ||
| Orange | 3 | ×1k (10^3) | - | 15 ppm/°C | ||
| Yellow | 4 | ×10k (10^4) | - | 25 ppm/°C | ||
| Green | 5 | ×100k (10^5) | ±0.5% | - | ||
| Blue | 6 | ×1M (10^6) | ±0.25% | 10 ppm/°C | ||
| Violet | 7 | ×10M (10^7) | ±0.1% | 5 ppm/°C | ||
| Gray | 8 | - | ±0.05% | - | ||
| White | 9 | - | - | - | ||
| Gold | - | ×0.1 | ±5% | - | ||
| Silver | - | ×0.01 | ±10% | - | ||
Standard Variants: IEC 60062 vs. SMD and Mil-Spec
A common point of confusion for makers transitioning from home wiring to electronics is the assumption that resistor colors have regional variants like wire insulation (e.g., NEC vs. IEC 60446 vs. old UK colors). They do not. Through-hole resistor color codes are universally governed by IEC 60062 globally. A Red-Black-Red resistor reads as 2k in Tokyo, Berlin, and Chicago.
However, you will encounter different packaging and precision standards that change how a 2k value is marked:
- IEC 60062 (Through-Hole): Uses the color bands detailed above. Universal for leaded components.
- EIA-96 / JIS (SMD Chip Resistors): A 2k SMD resistor will not have colors. For standard 5% tolerance, it will be marked 202 (20 × 10²). For 1% precision, it will be marked 2001 (200 × 10¹).
- MIL-PRF-55342 (Military/Aerospace): Uses a 5-band system but adds a distinct failure rate band (e.g., a Yellow band at the far right indicating a 0.001% failure rate per 1000 hours). The core 2k value remains Red-Black-Black-Brown.
Rows and Bands People Get Wrong on 2k Resistors
When reading a 2k resistor on the bench, three specific misidentifications cause the most troubleshooting headaches. Understanding these edge cases prevents swapping a 2k for a 3k or a 20-ohm resistor.
1. The Multiplier Trap: Red Digit vs. Red Multiplier
In the 4-band system, the third band is the multiplier. Because Red represents the digit '2', beginners often read Red-Black-Red as '2-0-2', calculating 202 ohms or 20.2 ohms. Remember that the multiplier band represents zeros added or powers of ten. Red in the multiplier position means ×10² (add two zeros). Therefore, 2-0 + two zeros = 2,000 ohms.
2. Bench Lighting: Red vs. Orange
Under warm 2700K LED bench lamps or in direct sunlight, the Orange band (Digit 3) can easily look Red (Digit 2). If you misread an Orange-Black-Red resistor as Red-Black-Red, you will think you have a 2k resistor when you actually have a 3k resistor. Always verify suspect bands under a 5000K daylight LED or use a digital multimeter (DMM).
3. Reading Backwards on 5-Band Resistors
On a 5-band 2k resistor (Red-Black-Black-Brown-Brown), the spacing between the multiplier and tolerance band is often too subtle to see on small 1/8W resistors. If you read it backwards, you get Brown-Brown-Black-Black-Red, which translates to 1-1-0-×1 (110 ohms). Rule of thumb: The tolerance band (Gold, Silver, or Brown) is almost always physically separated from the other bands by a slightly wider gap and is positioned on the right when the component leads point outward.
Decision Path: Identifying and Replacing Faded 2k Resistors
Carbon composition and older carbon film resistors degrade over time. Heat from the PCB or environmental humidity can cause the beige body to darken, turning Black bands into muddy Browns and Red bands into unreadable smudges. Use this decision tree to safely identify and replace a faded 2k resistor.
| Condition | Action Required | Expected Outcome |
|---|---|---|
| Bands are visible but colors are ambiguous (e.g., Red vs Orange). | Measure with DMM in Ohms mode. Ensure component is out of circuit or at least one leg is desoldered to avoid parallel path errors. | DMM reads between 1.9k and 2.1k (for a 5% part). Confirms 2k. |
| Bands are completely burned off or body is charred. | Do not trust the physical component; it has likely drifted due to thermal overload. Check the schematic or measure a known-good identical channel on the board. | Identify original design value. If schematic says 2k, discard the burned part. |
| Component is in-circuit and cannot be desoldered. | Use DMM. If reading is higher than 2k, the resistor is open or drifted. If reading is lower than 2k, you are measuring a parallel circuit path, not the resistor itself. | DMM reads ≤ 2.0k. If it reads 1.2k, the 2k resistor is likely fine, but paralleled with other board traces/components. |
| Need to order a modern, reliable replacement. | Upgrade from carbon film to metal film for better thermal stability and lower noise. | Select exact part: Vishay MRS25000C2001FCT00 (2.00kΩ, 1%, 0.4W, Metal Film). |
Practical Application: Where 2k Resistors Are Used
Understanding the 2k value goes beyond reading the bands; it requires knowing why a designer chose 2,000 ohms over 1k or 4.7k. Here are the three most common applications for a 2k resistor in modern electronics:
1. I2C Pull-Up Resistors (3.3V Systems)
In I2C communication, the SDA and SCL lines require pull-up resistors. For a 3.3V logic system running at standard mode (100 kHz), a 2k resistor provides an ideal balance. Using Ohm's Law (I = V/R), the sink current when the line is pulled low is 3.3V / 2000Ω = 1.65mA. This sits perfectly within the standard 3mA I2C sink limit while providing a fast enough RC rise time for bus capacitances up to ~200pF. (For deeper bus protocol hardware analysis, refer to All About Circuits' I2C primer).
2. BJT Base Current Limiting
When driving a standard NPN transistor (like a 2N2222 or BC547) from a 5V microcontroller GPIO, you must limit the base current. Assuming a Vbe drop of 0.7V, the voltage across the base resistor is 4.3V. A 2k resistor yields a base current of 2.15mA (4.3V / 2000Ω). With a typical hFE (gain) of 100, this allows the transistor to switch up to 215mA at the collector—more than enough to drive a small relay or high-power LED without overloading the microcontroller's 20mA GPIO limit.
3. LED Indicator Current Limiting (5V Supply)
For a standard red indicator LED (Vf ≈ 2.0V) on a 5V rail, a 2k resistor limits the current to exactly 1.5mA ((5V - 2V) / 2000Ω). While 20mA is the absolute maximum for most 3mm/5mm LEDs, 1.5mA to 2mA is the practical sweet spot for modern high-efficiency LEDs used as status indicators. It provides plenty of brightness while keeping power dissipation and heat generation negligible.
When stocking your lab, skip the loose, unsorted carbon film kits. Purchase a dedicated strip of Vishay MRS25 metal film resistors in 1% tolerance. The 1% tolerance ensures your 2k resistor is actually between 1.98k and 2.02k, eliminating the guesswork and drift associated with older 5% carbon components.
