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How to Calculate Degree Days

Updated February 21, 2017

Calculating degree days is important in calculating certain home or commercial heating or cooling requirements or calculating proper agricultural planting requirements. Regardless of the purpose of the calculation, the process for calculating degree days is the same. The general formula for calculating degree days is: Degree Days = Average daily temperature - Base temperature = (maximum + minimum) / 2 - Base temperature. For this example, assume a base of 10 degrees C with a minimum temperature of 7.22 degrees C and a maximum temperature of 21.1 degrees C.

Decide on the degree day base to use. This number will differ depending on, for example, the type of crop to be planted or the type of crop pest to be eradicated. For our example, we will use the arbitrary number of 50.

Calculate the average temperature by adding the maximum and minimum temperatures, then dividing by two. In this case, Average = 70 + 45 / 2, so Average = 57.7.

Calculate the degree days by subtracting the base from the average. Degree Days = 57.7 - 50. So, degree days = 7.7.

Use the degree days calculation to establish if the time is right for crop planting or pest eradication.

Tip

The degree day base you use will depend on what you want to establish. For example, the degree day base for one crop might be lower than for a crop that should be planted later in the season.

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About the Author

Although he grew up in Latin America, Mr. Ma is a writer based in Denver. He has been writing since 1987 and has written for NPR, AP, Boeing, Ford New Holland, Microsoft, RAHCO International, Umax Data Systems and other manufacturers in Taiwan. He studied creative writing at Mankato State University in Minnesota. He speaks fluent Mandarin Chinese, English and reads Spanish.