1k Ohm Resistor Color Code — Voltage Divider & Pull-Up Strength

1 kΩ (1000 Ω): Brown · Black · Red · Gold

Digits 1 · 0, multiplier ×100 → 1 kΩ. This guide is about voltage dividers and pull-up strength — not I²C (see 4.7 kΩ I²C guide) or megohm circuits (1 MΩ guide).

4-band: Brown · Black · Red · Gold → 10 × 100 = 1,000 Ω = 1 kΩ (±5%) · 5-band (±1%): Brown · Black · Black · Brown · Brown → 100 × 10 = 1 kΩ (±1%)

Worked voltage divider (identify two 1 kΩ parts, get 2.5 V from 5 V)

Use two 1 kΩ ±5% resistors in series — equal values → equal split:

Node	Ideal	With ±5% worst case
Top to mid	2.5 V	2.38 – 2.63 V
Mid to GND	2.5 V	same

Formula: $V_{out} = V_{in} × R_2 / (R_1 + R_2)$. For equal 1 kΩ: half the supply.

Critical: divider output sags under load. If an ADC input draws current, recalculate with load resistance in parallel — use our voltage divider calculator.

Pull-up strength: why choose 1 kΩ over 10 kΩ?

Pull-up R	@ 5 V idle current	Rise time (short trace)	Best for
1 kΩ	5 mA	Fast	Buttons, fast open-drain, short wires
4.7 kΩ	1.1 mA	Medium	I²C on short bus
10 kΩ	0.5 mA	Slower	Default GPIO, low power

Stronger pull-ups waste power but fight noise — weak pull-ups save battery but need clean PCB layout.

The 5-band 1 kΩ trap (read this before sorting reels)

Reel label	Bands	Actual value
1 kΩ ±1%	Brown · Black · Black · Brown · Brown	100 × 10 = 1 kΩ
100 Ω ±1%	Brown · Black · Black · Black · Brown	100 × 1 = 100 Ω

The fourth band is the multiplier on 5-band parts — not the third. Mixing these reels breaks divider ratios.

FAQ

1k vs 1000 ohms?

Same value. Color code: Brown-Black-Red-Gold (4-band).

Can 1 kΩ replace 10 kΩ on I²C?

Only on very short, slow buses — see the dedicated 4.7 kΩ I²C page for rise-time limits.

Related guides (different topics)

• 10 kΩ color code — button pull-ups & NTC dividers

• 4.7 kΩ color code — I²C rise time & bus capacitance

• 220 Ω color code — LED brightness vs 330/470 Ω on 5 V

• Values hub — pick by application

• How to read any resistor (method)

• Decode bands online