A 1.5 kOhm resistor has a nominal resistance of 1,500 ohms. In a standard four-band resistor color code, the value bands are brown, green, and red:
\(\displaystyle 15 \times 100 = 1{,}500\ \Omega = 1.5\ \text{k}\Omega\)
The resistor value may be used in a voltage-divider network, a transistor base circuit, an LED current-limiting calculation, a pull-up or pull-down circuit, or another branch-circuit control or signal application. The color bands identify nominal resistance; they do not by themselves establish the resistor’s wattage, maximum working voltage, temperature behavior, or suitability for the connected load.
Resistance Value and Unit Conversion
Ohms and kilohms express the same electrical resistance on different scales:
\(\displaystyle 1\ \text{k}\Omega = 1{,}000\ \Omega\)
Therefore:
| Value in ohms | Value in kilohms | Nominal resistor value |
|---|---|---|
| 1,500 Ω | 1.5 kΩ | Same value |
| 150 Ω | 0.15 kΩ | Different value |
| 150,000 Ω | 150 kΩ | Different value |
Changing the displayed unit from 1,500 Ω to 1.5 kΩ does not change the required resistor color code. The significant digits remain 1 and 5, and the multiplier remains \(\times 100\).
Four-Band Color Code
For a conventional four-band 1.5 kOhm resistor:
| Band position | Color | Meaning |
|---|---|---|
| First significant digit | Brown | 1 |
| Second significant digit | Green | 5 |
| Multiplier | Red | \(\times 100\) |
| Tolerance | Separate band | Allowed resistance variation |
The value calculation is:
\(\displaystyle \text{Resistance} = 15 \times 100 = 1{,}500\ \Omega\)
A common example is:
Brown – Green – Red – Gold
Gold is a common tolerance band and represents ±5% tolerance. With that tolerance, the actual measured resistance may fall within:
\(\displaystyle 1{,}500\ \Omega \times 0.05 = 75\ \Omega\)
\(\displaystyle 1{,}500\ \Omega - 75\ \Omega = 1{,}425\ \Omega\)
\(\displaystyle 1{,}500\ \Omega + 75\ \Omega = 1{,}575\ \Omega\)
So a nominal 1.5 kΩ resistor with a gold tolerance band may measure from 1,425 Ω to 1,575 Ω under appropriate measurement conditions.
Five-Band Resistor Identification
A five-band resistor uses three significant digits rather than two. Do not apply the four-band brown-green-red sequence to a five-band component without first identifying the band count and reading direction.
For example, a five-band 1.5 kΩ resistor may use a three-digit sequence that resolves to 150 followed by a multiplier that produces 1,500 Ω. The tolerance band is still read separately, normally at the end of the sequence and often spaced farther from the value bands.
Read the resistor from the end where the bands are grouped more closely. The tolerance band is commonly separated by a larger gap, although paint wear, body shape, and manufacturer marking practices can make visual identification less certain.
Voltage Divider Example
A 1.5 kΩ resistor is often used as one leg of a voltage divider. For two series resistors, the output voltage across the lower resistor is:
\(\displaystyle V_{out} = V_{in} \times \frac{R_2}{R_1 + R_2}\)
With a 12 V source, a 1.5 kΩ upper resistor, and a 1.5 kΩ lower resistor:
\(\displaystyle V_{out} = 12 \times \frac{1.5\ \text{k}\Omega}{1.5\ \text{k}\Omega + 1.5\ \text{k}\Omega}\)
\(\displaystyle V_{out} = 6\ \text{V}\)
The matching resistor values produce an unloaded midpoint voltage of 6 V. A connected load can change the actual output because the load becomes part of the circuit resistance. Resistor tolerance also affects the divider ratio.
Use the Resistor Color Code Calculator to confirm the band sequence and nominal value. Use the Voltage Divider Calculator to calculate the divider output after the resistor values are established.
Circuit Current and Resistor Power
Resistance alone does not establish whether a resistor is suitable for a circuit. Circuit current and power dissipation must be checked against the component rating.
Ohm’s law gives the current through a resistor:
\(\displaystyle I = \frac{V}{R}\)
For 12 V applied across a 1.5 kΩ resistor:
\(\displaystyle I = \frac{12}{1{,}500} = 0.008\ \text{A}\)
\(\displaystyle I = 8\ \text{mA}\)
Resistor power is:
\(\displaystyle P = \frac{V^2}{R}\)
\(\displaystyle P = \frac{12^2}{1{,}500} = 0.096\ \text{W}\)
The calculated dissipation is 0.096 W. The selected resistor must have a suitable wattage rating for the actual circuit voltage, expected loading, ambient temperature, enclosure conditions, and manufacturer specifications. A 1.5 kΩ value can appear on a low-voltage control circuit, but it is not automatically appropriate for a particular branch circuit, feeder control system, or electronic assembly.
Use the Ohm’s Law Calculator to check voltage, current, resistance, and power relationships before energizing the circuit.
Field Verification
Verify the resistor body and circuit requirements before installation or replacement:
- Confirm whether the component has four, five, or six color bands.
- Read the tolerance band separately from the significant-digit and multiplier bands.
- Check the measured resistance with a meter when circuit conditions allow accurate testing.
- Confirm the resistor wattage, voltage rating, package style, and temperature characteristics.
- Review the manufacturer data when the circuit has precision, heat, surge, safety, or reliability requirements.
- Isolate the resistor from parallel circuit paths when an in-circuit resistance measurement produces an unexpected reading.
Brown-green-red identifies a 1,500 Ω nominal resistance when used as the first two digits and \(\times 100\) multiplier. Final component approval requires the correct band count, tolerance, wattage, and manufacturer data—not color decoding alone.