# 1k resistor is 1000 ohms

The 1,000Ω resistor (often referred to as 1k), is commonly seen in circuit schematics.

One nice thing about the 1,000 ohm resistor is that for every volt across it, one milliamp of current will flow through it. If you put 10 volts across a 1k resistor, then 10mA of current will flow through it.

12 volts is more than what you want to put across a 1k resistor that has a wattage rating of 1/4W (0.25W). Most resistors are rated for 1/4W. 12V/1,000Ω = 0.012A (12mA). 0.012A x 12V = 0.144W. That is more than 0.125W, which is half of 0.25W. It is generally recommended to stay below half of a resistors wattage rating.

However, you will often see 1k resistors in circuits power by 12 volts because other components that are in series with the 1k resistor drop or divide some of that 12V. A series red indicator LED drops about 2V of the 12V from the 1k resistor. That means that there is 10V/1,000Ω  = 0.01A (10mA) of current flowing through the 1k resistor (and LED). Which means that there is 0.01A x 10V = 0.1W (100mW) of power that the resistor must be able to dissipate. That’s below half of 1/4W (0.25W), which is recommended for a 1/4W resistor.

• 220Ω
• 470Ω
• 1,000Ω
• 10,000Ω