Resistor
Limits current and divides voltage. Its value is printed in colored bands.
How it works
A resistor restricts how much current flows for a given voltage (Ohm's law: V = I × R). In maker projects they limit LED current, act as pull-up/pull-down resistors on inputs, and form voltage dividers.
Resistors are not polarized — they work either way around. The resistance value is read from the colored bands (see below), and the tolerance band (usually gold = ±5%) tells you how accurate it is.
Resistor color code
Read the bands from the grouped end: first two are digits, the third is the multiplier, and the last (gold/silver, slightly separated) is the tolerance.
220 Ω
Red · Red · Brown · Gold
330 Ω
Orange · Orange · Brown · Gold
1 kΩ
Brown · Black · Red · Gold
10 kΩ
Brown · Black · Orange · Gold
Band values
Black0 · ×1
Brown1 · ×10
Red2 · ×100
Orange3 · ×1k
Yellow4 · ×10k
Green5 · ×100k
Blue6 · ×1M
Violet7 · ×10M
Grey8 · —
White9 · —
Tolerance: Gold ±5%, Silver ±10%.
At a glance
- Common values
- 220 Ω, 330 Ω, 1 kΩ, 4.7 kΩ, 10 kΩ
- Tolerance
- Gold ±5%, Silver ±10%
- Power rating
- ¼ W (0.25 W) is standard for hobby use
Tips
- 220–330 Ω is the go-to LED current-limiting resistor at 5 V.
- 10 kΩ is the typical pull-up/pull-down value.
- Read the bands from the end with bands grouped closest; the tolerance band is on the far end.