Select a resistor. Find a resistor that you want to find out the temperature coefficient of. It can be any resistor and have any resistance value. Preferably, use a resistor with a value of one thousand or ten thousand ohms. For this example, we'll assume a resistor of 1,000 ohms.
Measure and record the resistor value at a temperature of 85 degrees centigrade. For this example, the resistor value at 85 degrees centigrade is 1,010 ohms.
Measure and record the resistor value at a temperature of 0 degrees centigrade (place it in a refridgerator freezer to lower the temperature). For this example, the resistor value at 0 degrees centigrade is 990 ohms.
Calculate the change in resistor value. Subtract the resistor value measured at 85 degrees centigrade from the resistor value measured at 0 degrees centigrade. For this example, the resistor value measured at 85 degrees centigrade is 1,010 ohms and the resistor valued measured at 0 degrees Centigrade is 990 ohms. Since 1,010 minus 990 is 20 ohms, the change in resistor value is 20 ohms.
Calculate the change in temperature value. Subtract the higher temperature measurement from the lower temperature measurement. For this example, the higher temperature is 85 degrees centigrade and the lower temperature was 0 degrees centigrade. Since 85 minus 0 is 85, the answer is 85 degrees.
Calculate the value of the temperature coefficient. Divide the result of the resistor subtraction by the temperature subtraction. For this example, the result of the resistor subtraction is 20 ohms, and the result of the temperature subtraction is 85 degrees centigrade. Since 20 divided by 80 is .0.25, the temperature coefficient is 0.25. Or in other words, the value of the resistor changes 0.25 ohms for every one degree centigrade change.