When looking for calorie counts of grains, I often come across dry and cooked values. Often times a source will provide a value for a 1/4 cup grain, stating that this is equivalent for 1 cup cooked. This doesn’t seem reliable, since some grains might expand more than others. Is there a reliable source for calorie values, preferably in cups, for intact grains like wheat and rye berries, oat groats, etc?
The only accurate way to determine the calories for grains is to weigh and measure them dry. This is because the weight after cooking can vary based on how exactly you cooked the grain and how much water was absorbed during the cooking process. It’s also not accurate to measure by volume in general, because that can be effected by how tightly things are packed into a cup, etc.
For meal prepping purposes, I would recommend calculating the total calories of the dry grain based on weight prior to cooking, and then weigh your entire batch of cooked grains, and then calculate a ratio of cooked/dry weight (or vice versa), and then you can use that to calculate the calories in your cooked grain by weight.