300 Ohm Resistor: Complete Guide to Color Code, Specifications & Applications

As someone who has spent years designing PCBs and troubleshooting circuits, I can tell you that the 300 ohm resistor is one of those components that shows up in more designs than most engineers realize. Whether you’re limiting current to an LED, matching antenna impedance, or building audio circuits, understanding this specific resistance value is essential for any electronics project.

In this guide, I’ll walk you through everything you need to know about the 300 ohm resistor—from reading the color bands correctly to selecting the right type for your application.

What is a 300 Ohm Resistor?

A 300 ohm resistor is a passive electronic component that provides exactly 300 ohms of electrical resistance. This value sits comfortably in the E24 standard resistor series, making it widely available from virtually every electronics supplier.

The primary job of any resistor is to oppose current flow, and at 300 ohms, this component offers a moderate level of resistance suitable for many common circuit applications. When you apply Ohm’s Law (V = IR), a 300 ohm resistor will limit current to approximately 16.67mA when connected across a 5V supply—perfect for many indicator LED circuits.

300 Ohm Resistor Color Code

Reading resistor color bands correctly is a fundamental skill that saves hours of troubleshooting. Here’s how to identify a 300 ohm resistor across different band configurations:

4-Band 300 Ohm Resistor Color Code

The most common through-hole resistors use four color bands. For 300 ohms:

Band Position	Color	Value
1st Band (First Digit)	Orange	3
2nd Band (Second Digit)	Black	0
3rd Band (Multiplier)	Brown	×10
4th Band (Tolerance)	Gold	±5%

Reading: 3, 0, ×10 = 300Ω ±5%

With a ±5% tolerance, the actual resistance can range from 285Ω to 315Ω.

5-Band 300 Ohm Resistor Color Code

Precision resistors often use five bands for tighter tolerances:

Band Position	Color	Value
1st Band	Orange	3
2nd Band	Black	0
3rd Band	Black	0
4th Band (Multiplier)	Black	×1
5th Band (Tolerance)	Brown	±1%

Reading: 3, 0, 0, ×1 = 300Ω ±1%

6-Band 300 Ohm Resistor Color Code

For applications requiring temperature stability, six-band resistors add a temperature coefficient:

Band Position	Color	Value
1st Band	Orange	3
2nd Band	Black	0
3rd Band	Black	0
4th Band (Multiplier)	Black	×1
5th Band (Tolerance)	Gold	±5%
6th Band (Temp Coefficient)	Black	250 ppm/K

Quick Color Code Reference Chart

Resistance	4-Band Code	5-Band Code
300Ω	Orange-Black-Brown-Gold	Orange-Black-Black-Black-Gold
220Ω	Red-Red-Brown-Gold	Red-Red-Black-Black-Gold
330Ω	Orange-Orange-Brown-Gold	Orange-Orange-Black-Black-Gold
270Ω	Red-Violet-Brown-Gold	Red-Violet-Black-Black-Gold

Types of 300 Ohm Resistors

Not all resistors are created equal. The construction material significantly impacts performance characteristics:

Carbon Film Resistors

These are the workhorses of hobby electronics. Carbon film 300 ohm resistors offer decent stability at an affordable price point. They’re suitable for general-purpose applications where precision isn’t critical. Typical specifications include ±5% tolerance and power ratings from 1/8W to 1W.

Metal Film Resistors

When your circuit demands accuracy, metal film resistors deliver tolerances as tight as ±0.1%. They also exhibit better temperature stability and lower noise than carbon film alternatives. I typically spec these for analog signal paths and precision measurement circuits.

Wirewound Resistors

For power applications, wirewound 300 ohm resistors handle significant wattage—from 5W up to 300W in industrial versions. The trade-off is higher inductance, which makes them unsuitable for high-frequency circuits. You’ll find these in power supplies, load testing equipment, and motor control circuits.

SMD (Surface Mount) Resistors

Modern PCB designs favor surface mount components. SMD 300 ohm resistors use a numeric marking system:

SMD Code	Value
301	300Ω (3-digit)
3000	300Ω (4-digit)

Common package sizes include 0402, 0603, 0805, and 1206, with power ratings ranging from 0.03W to 0.5W.

Power Ratings and Selection Guide

Choosing the correct power rating prevents resistor failure. Use this formula:

P = I² × R or P = V² / R

For a 300 ohm resistor with 10mA current: P = (0.01)² × 300 = 0.03W

A 1/4W (0.25W) resistor provides adequate headroom for this application.

Common Power Ratings for 300 Ohm Resistors

Power Rating	Typical Applications
1/8W (0.125W)	Signal circuits, low-current LED indication
1/4W (0.25W)	General purpose, breadboard prototyping
1/2W (0.5W)	Moderate power circuits, multiple LEDs
1W	Power regulation, current sensing
5W+	Load testing, power dissipation, industrial

Practical Applications of 300 Ohm Resistors

LED Current Limiting

One of the most common uses for a 300 ohm resistor is protecting LEDs from overcurrent. Here’s the calculation:

With a 5V supply and a red LED (2V forward voltage, 10mA typical current): R = (5V – 2V) / 0.01A = 300Ω

This makes the 300 ohm resistor an excellent choice for many standard LED indicator circuits.

Antenna Impedance Matching

If you’ve worked with older TV antennas or FM dipoles, you’ve encountered 300 ohm twin-lead cable. This balanced transmission line matches the impedance of folded dipole antennas (approximately 275Ω). When connecting to modern 75Ω coaxial systems, a 4:1 balun performs the impedance transformation (300/75 = 4).

300 ohm impedance appears frequently in:

• FM radio antenna connections
• VHF/UHF television antennas
• Amateur radio dipole feedlines
• Professional audio balanced line impedance

Audio and Signal Circuits

In audio equipment, 300 ohms serves as a standard impedance value for:

• Headphone impedance matching
• Microphone input termination
• Line-level signal attenuation
• Balanced audio interface design

Voltage Dividers

A 300 ohm resistor paired with other values creates precise voltage division. Combined with a 100Ω resistor in a divider fed by 5V:

Vout = 5V × (100 / (300 + 100)) = 1.25V

Transistor Biasing

Setting the proper operating point for transistor amplifiers often requires specific resistance values. 300 ohms appears in base bias networks and emitter degeneration circuits where moderate current limiting is required.

How to Verify a 300 Ohm Resistor

Color codes can fade or be difficult to read under poor lighting. Always verify resistance values with a digital multimeter before installation in critical circuits:

1. Set your multimeter to the appropriate resistance range (typically 2kΩ)
2. Touch the probes to both resistor leads
3. Read the displayed value

A 300 ohm resistor with ±5% tolerance should measure between 285Ω and 315Ω.

300 Ohm vs. Similar Resistance Values

Understanding when to use 300 ohms versus nearby standard values helps optimize circuit design:

Value	Current at 5V	Best For
220Ω	22.7mA	Higher-brightness LEDs, heavier loads
270Ω	18.5mA	Slightly higher current than 300Ω
300Ω	16.7mA	Standard LED circuits, moderate loads
330Ω	15.2mA	Conservative LED current, lower power

The 300 ohm resistor provides a middle-ground option when 220Ω allows too much current and 330Ω restricts it excessively.

Calculating Resistor Combinations

If you don’t have a 300 ohm resistor on hand, combine other values:

Series Connection (adds resistance)

Two 150Ω resistors in series: 150 + 150 = 300Ω

Parallel Connection (reduces resistance)

Four 1.2kΩ resistors in parallel: 1200 / 4 = 300Ω

Combination	Configuration	Result
150Ω + 150Ω	Series	300Ω
100Ω + 200Ω	Series	300Ω
600Ω ∥ 600Ω	Parallel	300Ω
1.2kΩ ∥ 1.2kΩ ∥ 1.2kΩ ∥ 1.2kΩ	Parallel	300Ω

Useful Resources and Databases

Here are reliable sources for specifications, calculators, and purchasing:

Online Calculators

• DigiKey Resistor Color Code Calculator: digikey.com/en/resources/conversion-calculators/conversion-calculator-resistor-color-code
• Resistor Color Codes Reference: resistorcolorcodes.com
• Calculator.net Resistor Calculator: calculator.net/resistor-calculator.html

Component Suppliers

• DigiKey: Extensive selection with detailed datasheets
• Mouser Electronics: Wide range of specifications and tolerances
• Newark/Farnell: Industrial and precision components
• LCSC: Competitive pricing for volume orders

Technical Documentation

• IEC 60062: International standard for resistor color coding
• EIA Resistor Series: E12, E24, E48, E96 standard values

Frequently Asked Questions

What color bands identify a 300 ohm resistor?

A standard 4-band 300 ohm resistor displays Orange-Black-Brown-Gold bands, representing 3-0-×10-±5%. For 5-band precision versions, look for Orange-Black-Black-Black followed by a tolerance band.

Can I use a 330 ohm resistor instead of 300 ohm?

In most applications, yes. A 330Ω resistor provides 10% higher resistance, slightly reducing current flow. For LED circuits, this means marginally dimmer output but increased component lifespan. Always verify the substitution doesn’t violate minimum current requirements for your specific application.

What power rating should I choose for a 300 ohm resistor?

Calculate power dissipation using P = I²R, then select a resistor rated at least 50% higher than the calculated value. For most breadboard and low-power circuits, 1/4W (0.25W) resistors provide adequate margin. High-current applications may require 1/2W, 1W, or higher ratings.

Why is 300 ohm important for antenna systems?

300 ohms is the characteristic impedance of standard twin-lead transmission line, which naturally matches folded dipole antenna impedance (approximately 275Ω). This impedance matching minimizes signal reflection and power loss in FM radio, VHF television, and amateur radio installations.

How do I read the SMD marking for a 300 ohm resistor?

Surface mount 300 ohm resistors typically display “301” (3-digit code: 30 × 10¹ = 300Ω) or “3000” (4-digit code: 300 × 10⁰ = 300Ω). Some manufacturers use “R” to indicate a decimal point—”300R” means exactly 300.0Ω.

Conclusion

The 300 ohm resistor remains a staple component in electronics design, from simple LED indicators to professional antenna systems. Understanding its color code, specifications, and applications enables you to confidently specify the right component for your project.

Whether you’re building your first breadboard circuit or designing production PCBs, knowing how to identify, calculate, and apply 300 ohms of resistance is fundamental knowledge that serves you throughout your electronics journey.

Keep a stock of various tolerances and power ratings in your parts bin—the 300 ohm resistor has a habit of appearing exactly when you need it most.