diff --git a/modules/icing/pirep_goes.py b/modules/icing/pirep_goes.py
index dd86957e19936682589563fe5bbea86dc5926393..3083dcc7e154ecb84ed4176cddfd8f704c5f6f7f 100644
--- a/modules/icing/pirep_goes.py
+++ b/modules/icing/pirep_goes.py
@@ -946,7 +946,7 @@ def analyze2(filename, filename_l1b):
     precision = tp / (tp + fp)
     f1 = 2 * (precision * recall) / (precision + recall)
     mcc = ((tp * tn) - (fp * fn)) / np.sqrt((tp + fp) * (tp + fn) * (tn + fp) * (tn + fn))
-    acc = (tp + tn) / num_obs
+    acc = (tp + tn) / (tp + tn + fp + fn)
 
     print('Total (Positive/Icing Prediction: ')
     print('True icing:                         ', np.sum(true_ice))