How many calories are in oats?

Dry vs. cooked

Oats absorb roughly three times their weight in water as they cook. So 50 grams of dry oats turn into roughly 150 to 180 grams of porridge. Since water contributes no calories, the total energy stays the same — only the calories per 100 grams of prepared porridge drop, to around 70 calories. If you weigh your portion after cooking, use that figure to avoid miscounting.

Nutrition per 100 grams dry

Old-fashioned, quick, or instant oats

According to the BLS (Germany’s national food composition database), the flake types barely differ in energy content. Old-fashioned rolled, quick, finely milled, and instant oats all fall between 370 and 385 calories per 100 grams dry. The real difference lies in the glycemic index: per Atkinson et al. (2021), old-fashioned rolled oats have a GI of around 55, while instant oats sit markedly higher at 79 and spike blood sugar faster.

Overnight oats and porridge compared

A classic porridge made with 50 grams of oats and 250 ml of whole milk delivers around 350 calories. The same base with low-fat milk (1.5%) comes to roughly 310 calories, and with unsweetened oat milk to about 260 calories. Toppings like banana, honey, and nuts add another 100 to 250 calories — in many cases, the full bowl ends up at 500 to 650 calories.

Oats and muscle growth

Oats rank among the most popular carbohydrate sources in strength training: they provide long-lasting energy at a moderate glycemic index and contain around 13 grams of protein per 100 grams. In its position stand on carbohydrate intake, the ISSN lists oats as a suitable base for pre-workout meals, especially two to three hours before training.