Open the Excel file (GDD Calculator)

In this file you will find maximum and minimum temperatures for Castana, IA from the last spring 32°F (0° C) to first fall 32° F (0° C). Let's calculate the total season GDDs.

In cell G2 enter:
==IF(E2 > 86, 86, E2)

(This tells Excel to check if the value in cell E2 is greater than 86° F. If the statement is true, then the value in G2 is set to 86. If the statement is false then G2 is set to the maximum temperature for the day.)

In cell H2 enter:
==IF(F2 < 50, 50, F2)

(This performs the same function in testing the minimum temperature to be greater than 50° F.)

In cell I2 enter:
= (G2+H2)/2-50

(This calculates the daily contribution of GDDs)

In cell J2 enter:
= Sum($I$2:I2)

(This will sum the daily values in the I column from I2 to the current cell.

To calculate the whole table, drag the mouse to highlight cells G2 to J2. A small box will appear in the lower right hand corner of cell J2. Click your mouse on this box and drag down to fill out the rest of the growing season.