2.2k Ohm Resistor Color Code — Fast I²C Pull-Up & Red-Band Trap
2.2 kΩ color code (Red-Red-Red-Gold): when 4.7 kΩ is too weak on a capacitive I²C bus, rise-time math, and the 220 Ω vs 2.2 kΩ brown-vs-red decade trap.
Decode band colors instantly
Full index: All resistor color code values
2.2 kΩ: the stronger I²C pull-up (three red bands)
Red · Red · Red · Gold → digits 2 · 2, multiplier ×100 → 2.2 kΩ. Three red bands before gold is a distinctive pattern — but easy to confuse with 220 Ω if you misread the multiplier.
4-band: Red · Red · Red · Gold → 22 × 100 = 2,200 Ω = 2.2 kΩ (±5%) · 5-band (±1%): Red · Red · Black · Brown · Brown → 220 × 10 = 2.2 kΩ (±1%)
This guide is fast-mode I²C pull-up engineering — companion to the 4.7 kΩ I²C page. For GPIO buttons see 10 kΩ; for LEDs see 220 Ω.
When 4.7 kΩ is too weak — use 2.2 kΩ
I²C rise time scales with $R × C$. A capacitive breadboard bus may need half the pull-up resistance:
| Pull-up | @ 200 pF $C_b$ → $t_r$ (order) | Typical fit |
|---|---|---|
| 4.7 kΩ | ~800 ns | Short PCB, 100 kHz |
| 2.2 kΩ | ~370 ns | Fast mode, jumpers, multiple devices |
| 1 kΩ | ~170 ns | Aggressive — check driver $I_{OL}$ |
Rounded edges on the scope → lower $R$, not higher. Use our I²C pull-up calculator for your bus.
3.3 V vs 5 V (same color code)
| Rail | Idle current per line @ 2.2 kΩ | Notes |
|---|---|---|
| 5 V | ~2.3 mA | Higher power — OK on USB-powered boards |
| 3.3 V | ~1.5 mA | ESP32 / STM32 modules — same Red-Red-Red-Gold bands |
Supply voltage changes power dissipation, not the color code.
220 Ω vs 2.2 kΩ — brown vs red (catastrophic swap)
| Value | Multiplier band | 4-band |
|---|---|---|
| 220 Ω | Brown (×10) | Red · Red · Brown · Gold |
| 2.2 kΩ | Red (×100) | Red · Red · Red · Gold |
Plugging 220 Ω on I²C lines over-pulls the bus (~23 mA @ 5 V) and can prevent proper signaling. Always verify red-red parts with a meter — see also 220 Ω LED guide.
vs 4.7 kΩ and 1 kΩ — pick by bus, not habit
| Scenario | Start here |
|---|---|
| Battery, slow 100 kHz, short traces | 4.7 kΩ guide |
| Breadboard, 400 kHz, scope shows slow rise | 2.2 kΩ (this page) |
| Many devices, long cable, still failing | Try 1 kΩ — 1 kΩ divider/pull guide |
FAQ
What is the 2.2k ohm resistor color code?
4-band (±5%): Red, Red, Red, Gold. 22 × 100 = 2.2 kΩ (±5%). Actual range: 2.09 kΩ – 2.31 kΩ.
What is the 2.2k ohm resistor colour code (5-band)?
Red · Red · Black · Brown · Brown → 220 × 10 = 2.2 kΩ (±1%). Range: 2.178 kΩ – 2.222 kΩ.
How do I read a 2.2k ohm resistor color code?
Read left to right: first bands are digits, then multiplier, then tolerance. For 2.2 kΩ: Red-Red-Red = significant digits & multiplier, Gold = tolerance. Use the color code calculator to verify.
Which end do I start reading a 2.2 kΩ resistor from?
Start from the grouped digit bands (left). The tolerance band (Gold) is on the right — gold and silver are almost always tolerance, not multipliers.
What is the difference between 4-band and 5-band for 2.2 kΩ?
4-band (Red · Red · Red · Gold) gives 22 × 100 = 2.2 kΩ (±5%) with typical ±5% gold tolerance. 5-band (Red · Red · Black · Brown · Brown) adds a third digit for ±1% precision: 220 × 10 = 2.2 kΩ (±1%) (2.178 kΩ – 2.222 kΩ).
2.2k vs 220 ohm color code?
220 Ω uses brown multiplier (×10). 2.2 kΩ uses red (×100).
Related guides (different topics)
- 4.7 kΩ color code — I²C rise time & bus capacitance
- 220 Ω color code — LED brightness vs 330/470 Ω on 5 V
- 1 kΩ color code — divider math & strong pull-ups
Topic cluster
More resistor color code guides
Learn the method in our beginner's guide · Decode instantly with the color code calculator