A 4-band resistor color code converts four painted bands into a resistance value in ohms and a tolerance range. The value is used when checking a component against a schematic, selecting a replacement resistor, reviewing a voltage-divider network, or confirming the resistance used in an Ohm’s Law calculation.
The four-band method reads, in order:
- First significant digit
- Second significant digit
- Multiplier
- Tolerance
The first two bands establish the base number. The third band moves the decimal point by applying a power-of-ten multiplier. The separated band at the opposite end is normally the tolerance band and should be read last.
Band Direction and Tolerance
Start from the end where the first three bands are grouped closer together. On most axial resistors, the tolerance band has a larger gap before it and is often gold or silver.
A resistor marked with a gold tolerance band is commonly read as ±5%. A 150 Ω resistor with ±5% tolerance can measure anywhere from:
\(\displaystyle 150\ \Omega \times 0.95 = 142.5\ \Omega\)
to:
\(\displaystyle 150\ \Omega \times 1.05 = 157.5\ \Omega\)
Tolerance is not another digit in the resistance value. It defines the permitted manufacturing variation around the marked nominal resistance.
Four-Band Color Code Formula
The resistance calculation is:
\(\displaystyle R = (10A + B) \times M\)
Where:
- (A) is the first digit band
- (B) is the second digit band
- (M) is the multiplier from the third band
- The fourth band supplies the tolerance
For the examples below, brown represents 1 and green represents 5. Those first two bands form the number 15. Changing only the multiplier creates 150 Ω, 1.5 kΩ, or 150 kΩ.
| Band position | Function | 150 Ω example |
|---|---|---|
| First band | First digit | Brown = 1 |
| Second band | Second digit | Green = 5 |
| Third band | Multiplier | Brown = ×10 |
| Fourth band | Tolerance | Gold = ±5% |
150 Ohm Resistor Color Code
A 150 Ω resistor with ±5% tolerance is:
Brown – Green – Brown – Gold
The calculation is:
\(\displaystyle 15 \times 10 = 150\ \Omega\)
This value appears in low-voltage control circuits, LED current-limiting applications, signal conditioning, pull-up or pull-down networks, and basic electronics troubleshooting. The resistor’s wattage rating must also be suitable for the circuit power dissipation:
\(\displaystyle P = I^2R\)
or
\(\displaystyle P = \frac{V^2}{R}\)
Resistance value alone does not establish whether a replacement is acceptable. Confirm resistance, tolerance, wattage, voltage rating where applicable, and component construction.
For a value-specific breakdown, see 150 Ohm Resistor Color Code.
1.5 kOhm Resistor Color Code
A 1.5 kΩ resistor is the same base digits, 15, with a larger multiplier:
Brown – Green – Red – Gold
Red is a multiplier of ×100:
\(\displaystyle 15 \times 100 = 1{,}500\ \Omega\)
\(\displaystyle 1{,}500\ \Omega = 1.5\ \text{k}\Omega\)
The first two bands did not change. Brown and green still equal 15. Only the third band changed from brown, ×10, to red, ×100.
A 1.5 kΩ resistor may be used where a circuit needs less current than a 150 Ω value would permit. For example, in a 5 V circuit with the resistor treated as the only load:
\(\displaystyle I = \frac{V}{R} = \frac{5}{1{,}500} = 0.00333\ \text{A}\)
That is approximately 3.33 mA. Actual circuit current depends on all connected components and voltage drops, not just the resistor value.
See 1.5 kOhm Resistor Color Code for the full color-band reference.
150 kOhm Resistor Color Code
A 150 kΩ resistor again begins with brown and green:
Brown – Green – Yellow – Gold
Yellow is a multiplier of ×10,000:
\(\displaystyle 15 \times 10{,}000 = 150{,}000\ \Omega\)
\(\displaystyle 150{,}000\ \Omega = 150\ \text{k}\Omega\)
Higher resistance values such as 150 kΩ are common in sensing, timing, biasing, voltage-divider, and high-impedance signal circuits. A meter reading can be affected by parallel circuit paths, capacitors, semiconductor junctions, contamination, or measuring the resistor while it remains connected in the circuit.
For a dedicated reference, use 150 kOhm Resistor Color Code.
Multiplier Comparison
| Nominal resistance | Color bands | Base digits | Multiplier calculation |
|---|---|---|---|
| 150 Ω | Brown – Green – Brown – Gold | 15 | \(15 \times 10\) |
| 1.5 kΩ | Brown – Green – Red – Gold | 15 | \(15 \times 100\) |
| 150 kΩ | Brown – Green – Yellow – Gold | 15 | \(15 \times 10{,}000\) |
The multiplier band controls the order of magnitude:
- Brown multiplier: ×10
- Red multiplier: ×100
- Yellow multiplier: ×10,000
A wrong multiplier can create a substantial circuit error. Replacing 150 kΩ with 150 Ω changes the resistance by a factor of 1,000, which can alter current, voltage drop, timing behavior, and component heating.
Resistor Color Code Calculator
Use the Resistor Color Code Calculator to select the four band colors and confirm the nominal resistance and tolerance. The calculation follows the same sequence: two significant digits, multiplier, then tolerance.
Use the Ohm’s Law Calculator after identifying the resistance value when reviewing voltage, current, resistance, or power in the circuit.
For example, after confirming a resistor is 1.5 kΩ, an Ohm’s Law review can estimate current through that resistance at a known voltage. That result supports component-level circuit verification; it does not replace a complete analysis of connected loads, source limitations, or branch-circuit protection.
Field Verification
A four-band color code applies to conventional resistors with two digit bands, one multiplier band, and one tolerance band. Verify separately when any of the following conditions apply:
- The resistor has five or six bands.
- Paint is faded, burned, contaminated, or physically damaged.
- The component is a surface-mount resistor with printed markings rather than color bands.
- The part uses a nonstandard package or manufacturer-specific marking system.
- An in-circuit meter reading differs from the marked value because other components create parallel paths.
Disconnect power before resistance testing. For reliable resistance measurement, isolate at least one resistor lead when the surrounding circuit can affect the reading.
For additional references, see the Resistor Color Code Chart for 150 Ohm, 1.5 kOhm, and 150 kOhm and Resistor Tolerance Bands Explained.