4.7K Resistor: Color Code & Pull-up Uses (Complete PCB Engineer Guide)

As someone who’s designed hundreds of PCB boards over the years, I can tell you that the 4.7 k ohm resistor is one of those components you’ll reach for again and again. Whether you’re building your first Arduino project or designing a professional I2C bus, understanding this workhorse resistor inside and out will save you hours of debugging time. In this guide, I’ll walk you through everything from reading the color bands to calculating optimal pull-up configurations—the practical stuff they don’t always teach in textbooks.

What is a 4.7 Kilo Ohm Resistor?

A 4.7 kilo ohm resistor (also written as 4.7kΩ, 4k7, or 4700Ω) is a passive electronic component with a resistance value of 4,700 ohms. The “k” stands for kilo, meaning 1,000, so 4.7k simply means 4.7 × 1,000 = 4,700 ohms.

This specific resistance value sits in a sweet spot that makes it incredibly versatile. It’s low enough to provide decent current flow and fast signal rise times, yet high enough to minimize power consumption. That balance is exactly why you’ll find the 4.7 k ohm resistor specified in countless reference designs and application notes, particularly for I2C pull-up applications.

Key Specifications of 4.7K Resistors

Parameter	Typical Value	Notes
Resistance	4,700Ω (4.7kΩ)	Nominal value
Common Tolerances	±1%, ±5%, ±10%	5% most common for general use
Power Rating (THT)	1/4W (0.25W), 1/8W	Match to your circuit requirements
Power Rating (SMD)	0402 to 2512 packages	Based on package size
Max Voltage (1/4W)	~34V	Calculated from P = V²/R
Temperature Coefficient	50-250 ppm/°C	Varies by resistor type

4.7K Ohm Resistor Color Code: How to Read It

Reading resistor color codes becomes second nature with practice, but even experienced engineers occasionally need a refresher. The 4.7 k ohm resistor uses a straightforward color band system that tells you everything you need to know at a glance.

4-Band Resistor Color Code for 4.7K

The most common through-hole 4.7kΩ resistors use four color bands:

Band Position	Color	Value/Meaning
1st Band	Yellow	First digit: 4
2nd Band	Violet (Purple)	Second digit: 7
3rd Band	Red	Multiplier: ×100
4th Band	Gold or Silver	Tolerance: ±5% or ±10%

Calculation: 47 × 100 = 4,700Ω = 4.7kΩ

The sequence Yellow-Violet-Red-Gold is what you’re looking for. I’ve trained myself to instantly recognize this pattern—it’s worth committing to memory since you’ll encounter it constantly.

5-Band Resistor Color Code for 4.7K (High Precision)

For tighter tolerance applications, 5-band resistors add an extra significant digit:

Band Position	Color	Value/Meaning
1st Band	Yellow	First digit: 4
2nd Band	Violet	Second digit: 7
3rd Band	Black	Third digit: 0
4th Band	Brown	Multiplier: ×10
5th Band	Brown	Tolerance: ±1%

Calculation: 470 × 10 = 4,700Ω = 4.7kΩ

The 5-band sequence is Yellow-Violet-Black-Brown-Brown for a 1% tolerance 4.7 kilo ohm resistor.

Quick Color Code Reference Table

Color	Digit Value	Multiplier	Tolerance
Black	0	×1	—
Brown	1	×10	±1%
Red	2	×100	±2%
Orange	3	×1,000	—
Yellow	4	×10,000	—
Green	5	×100,000	±0.5%
Blue	6	×1,000,000	±0.25%
Violet	7	×10,000,000	±0.1%
Gray	8	—	±0.05%
White	9	—	—
Gold	—	×0.1	±5%
Silver	—	×0.01	±10%

SMD Resistor Code for 4.7K

Surface mount resistors use numeric codes instead of color bands. For a 4.7k SMD resistor, the marking is 472:

• First two digits (47): Significant figures
• Third digit (2): Number of zeros to add, or multiplier (10²)
• Result: 47 × 10² = 4,700Ω

For high-precision 4-digit SMD codes, you might see 4701 (470 × 10¹ = 4,700Ω) on 1% tolerance parts.

Quick tip: When you see “472” on a tiny chip resistor, think “47 followed by 2 zeros” = 4,700.

Understanding Tolerance and Its Impact

The tolerance band determines how much the actual resistance can deviate from the stated value. Here’s what that means in practice for a 4.7 k ohm resistor:

Tolerance	Range (Ω)	Best For
±1%	4,653 – 4,747	Precision circuits, sensors, amplifiers
±5%	4,465 – 4,935	General purpose, pull-ups, current limiting
±10%	4,230 – 5,170	Non-critical applications, prototyping

For most pull-up resistor applications, a 5% tolerance 4.7 kilo ohm resistor works perfectly fine. The I2C spec allows for a fairly wide range of pull-up values, so the variation won’t cause issues. However, if you’re designing a precision voltage divider or sensor interface, spring for the 1% tolerance parts—the small cost difference is worth the predictability.

4.7K Resistor as a Pull-up Resistor

This is where the 4.7 k ohm resistor really shines. Pull-up (and pull-down) resistors are essential in digital circuits to ensure signal lines rest at a known logic state when not actively driven.

Why 4.7K is Ideal for Pull-ups

Pull-up resistors connect a signal line to VCC (usually 3.3V or 5V), ensuring the line reads HIGH when nothing else is driving it. The 4.7 kilo ohm resistor hits a practical sweet spot for several reasons:

1. Fast rise times: Lower resistance values charge bus capacitance more quickly, enabling sharper signal transitions
2. Reasonable current draw: At 5V, a 4.7kΩ pull-up draws about 1mA when pulled low—acceptable for most applications
3. Reliable logic levels: Provides strong enough pull-up to overcome noise and ensure clean HIGH states
4. Widely available: Stocked by every distributor, in every package size

I2C Pull-up Resistor Applications

The most common application for 4.7K pull-up resistors is on I2C (Inter-Integrated Circuit) communication buses. I2C uses an open-drain architecture where devices can only pull lines LOW—they rely on external resistors to pull lines back to HIGH.

Standard I2C configuration:

• One 4.7kΩ resistor on SDA (data line) to VCC
• One 4.7kΩ resistor on SCL (clock line) to VCC

This configuration works reliably for most I2C setups at standard (100kHz) and fast mode (400kHz) speeds with moderate bus capacitance.

Calculating Optimal Pull-up Values

The I2C specification provides formulas to determine the acceptable pull-up resistor range:

Minimum resistance (to avoid exceeding sink current):

Rp(min) = (VCC – VOL(max)) / IOL

For a 5V system: Rp(min) = (5V – 0.4V) / 3mA ≈ 1.5kΩ

Maximum resistance (for acceptable rise time):

Rp(max) = tr / (0.8473 × Cb)

Where tr = rise time (1000ns for standard mode) and Cb = bus capacitance.

For a typical setup with 100pF bus capacitance: Rp(max) ≈ 11.8kΩ

The 4.7 k ohm resistor falls comfortably within this range, making it a safe default choice.

Pull-up Resistor Selection Guide

I2C Speed Mode	Typical Capacitance	Recommended Pull-up
Standard (100kHz)	Up to 400pF	4.7kΩ – 10kΩ
Fast (400kHz)	Up to 400pF	2.2kΩ – 4.7kΩ
Fast Plus (1MHz)	Up to 550pF	1kΩ – 2.2kΩ
High Speed (3.4MHz)	Up to 100pF	Custom calculation

When to adjust from 4.7kΩ:

• Go lower (2.2kΩ – 3.3kΩ): Long wire runs, multiple devices, high-speed operation, noisy environments
• Go higher (10kΩ): Battery-powered devices where minimizing current draw is critical, single-device short traces

Other Common Applications for 4.7K Resistors

Beyond pull-ups, the 4.7 kilo ohm resistor serves many purposes in circuit design.

Voltage Dividers

A voltage divider with two resistors can scale down voltages for ADC inputs or level shifting. Pairing a 4.7kΩ resistor with a 10kΩ resistor creates approximately a 3:1 division ratio.

Example: Converting 5V logic to 3.3V tolerant levels using 4.7kΩ (top) and 10kΩ (bottom) creates a voltage divider that outputs approximately 3.4V—close enough for most 3.3V inputs.

LED Current Limiting

While not the most common choice for LEDs, a 4.7 k ohm resistor can limit current for indicator LEDs in low-power applications:

• At 5V with typical 2V LED forward voltage: I = (5V – 2V) / 4.7kΩ ≈ 0.64mA (dim but visible)
• At 3.3V with typical 2V LED forward voltage: I = (3.3V – 2V) / 4.7kΩ ≈ 0.28mA (very dim)

This works for status indicators where brightness isn’t critical, but you’ll want lower values (220Ω – 1kΩ) for standard brightness.

Transistor Biasing

The 4.7 k ohm resistor is commonly used in transistor biasing networks to set the operating point of BJT amplifiers, ensuring linear operation and minimizing distortion.

RC Timing Circuits

Combined with capacitors, a 4.7kΩ resistor creates predictable timing elements:

Capacitor	Time Constant (τ)	Use Case
1µF	4.7ms	Button debouncing
100nF	470µs	Filter circuits
10nF	47µs	High-frequency filtering

Comparing 4.7K vs 10K vs 47K Resistors

Engineers often debate whether to use 4.7kΩ, 10kΩ, or 47kΩ for pull-ups. Here’s a practical comparison:

Parameter	4.7kΩ	10kΩ	47kΩ
Current at 5V	1.06mA	0.5mA	0.1mA
Rise time	Faster	Medium	Slower
Noise immunity	Better	Good	Lower
Power consumption	Higher	Medium	Lower
Best for	I2C, fast signals	General pull-ups	Ultra-low power

My recommendation: Start with 4.7kΩ for I2C and signals where speed matters. Use 10kΩ for general-purpose pull-ups on slower digital inputs. Reserve 47kΩ for battery-powered applications where every microamp counts.

Common Mistakes and How to Avoid Them

After reviewing countless designs (including my own early mistakes), here are pitfalls to watch for:

Mistake 1: Using 10kΩ for Fast I2C

A 10kΩ pull-up often works at 100kHz but causes communication failures at 400kHz due to slow rise times. Use 4.7kΩ or lower for fast-mode I2C.

Mistake 2: Forgetting Multiple Pull-ups Add in Parallel

If multiple I2C devices each have their own pull-up resistors, they combine in parallel. Three devices with 4.7kΩ pull-ups each result in an effective pull-up of about 1.57kΩ, which might be too strong. Check your breakout boards and disable extra pull-ups when necessary.

Mistake 3: Ignoring Bus Capacitance

Longer I2C traces and more devices increase bus capacitance, requiring stronger (lower value) pull-ups. Measure with an oscilloscope to verify clean signal edges.

Mistake 4: Confusing 4.7K with 47K

The color codes are similar (Yellow-Violet-Red vs Yellow-Violet-Orange). Always double-check the multiplier band—a 47kΩ resistor where you intended 4.7kΩ can cause subtle, hard-to-debug issues.

Useful Resources and Tools

Here are tools and databases I regularly use when working with resistors:

Online Calculators

• DigiKey Resistor Color Code Calculator — Decodes 4, 5, and 6-band resistors
• DigiKey SMD Resistor Code Calculator — Converts 3-digit, 4-digit, and EIA-96 codes
• All About Circuits Resistor Calculator — Interactive tool with visual representation
• Calculator.net Resistor Calculator — Includes series/parallel calculations

Component Datasheets and Suppliers

• DigiKey — Extensive parametric search for resistors
• Mouser Electronics — Wide selection with datasheets
• LCSC — Cost-effective SMD resistors, especially for JLCPCB assembly
• Octopart — Cross-distributor search and comparison

Technical References

• Texas Instruments I2C Pull-up Calculation (SLVA689) — Detailed formulas for I2C pull-up sizing
• NXP I2C-bus Specification — The definitive I2C reference
• SparkFun I2C Tutorial — Beginner-friendly explanation of I2C and pull-ups
• Total Phase I2C Pull-up Guide — Practical pull-up selection guidance

Mobile Apps

• Search “Resistor Color Code Calculator” in your app store — Several free apps use your phone camera to identify resistor values

Frequently Asked Questions (FAQs)

What is the color code for a 4.7K ohm resistor?

The 4-band color code for a 4.7K ohm resistor is Yellow-Violet-Red-Gold (for 5% tolerance). Yellow represents the digit 4, violet represents 7, red is the multiplier (×100), and gold indicates ±5% tolerance. This gives you 47 × 100 = 4,700 ohms or 4.7kΩ. For 5-band precision resistors (1% tolerance), the sequence is Yellow-Violet-Black-Brown-Brown.

What is the difference between 4.7K and 47K resistors?

The main difference is the resistance value—4.7kΩ (4,700 ohms) versus 47kΩ (47,000 ohms). The 47K resistor has 10 times higher resistance, meaning it allows 10 times less current to flow for the same voltage. This affects their suitability for different applications. In color code terms, the 4.7K uses a red multiplier band (×100) while the 47K uses an orange multiplier band (×1,000). The 4.7 kilo ohm resistor is preferred for I2C pull-ups due to faster rise times, while 47K might be used for ultra-low power applications.

Why is 4.7K commonly used for I2C pull-up resistors?

The 4.7K resistor is popular for I2C pull-ups because it provides an excellent balance between signal rise time and power consumption. I2C buses use open-drain outputs that require external pull-ups to return to HIGH state. A 4.7kΩ resistor charges the bus capacitance fast enough for reliable 100kHz and 400kHz operation while drawing only about 1mA at 5V when the line is pulled low. It falls safely within the I2C specification’s recommended range (typically 1.5kΩ to 10kΩ for standard setups).

Can I use a 10K resistor instead of 4.7K for pull-ups?

Yes, in many cases a 10kΩ resistor works fine as a pull-up, especially for standard-mode (100kHz) I2C or general digital inputs. However, 10kΩ may cause issues with fast-mode I2C (400kHz) due to slower rise times, particularly with longer wire runs or multiple devices adding bus capacitance. The higher resistance also provides slightly weaker noise immunity. If you’re experiencing intermittent communication errors, switching from 10kΩ to 4.7kΩ often resolves the problem. For battery-powered devices where current consumption is critical, 10kΩ saves about half the quiescent current.

What does 472 mean on an SMD resistor?

The code “472” on an SMD (surface mount) resistor indicates a 4.7K ohm resistance value. The marking system works like this: the first two digits (47) are the significant figures, and the third digit (2) tells you how many zeros to add, acting as a multiplier (10²). So 472 means 47 × 10² = 47 × 100 = 4,700 ohms = 4.7kΩ. This 3-digit code system is standard for 5% tolerance SMD resistors. Higher precision 1% resistors may use a 4-digit code (4701) or the EIA-96 alphanumeric system.

Summary

The 4.7 k ohm resistor is a fundamental component that every electronics engineer and hobbyist should understand thoroughly. Its versatility in pull-up configurations, particularly for I2C buses, makes it an essential part of any component kit. Remember the Yellow-Violet-Red-Gold color code (or 472 for SMD), understand when to adjust values based on your specific application requirements, and always verify critical designs with an oscilloscope when possible.

Whether you’re building your first sensor project or designing production PCBs, having solid fundamentals with components like the 4.7 kilo ohm resistor will serve you well throughout your engineering career.