The question “Which nut has the fewest calories?” has a clear outlier: chestnuts. They provide roughly 200–250 calories and only a few grams of fat per 100 g, versus about 718 calories and 76 g fat in macadamias.
Calories per 100 g and per ounce
| Nut | Approx. kcal/100 g | Approx. kcal/1 oz |
|---|---|---|
| Chestnuts | ~200–250 | ~56–70 |
| Cashews | ~553 | ~155 |
| Pistachios | ~560 | ~157 |
| Almonds | ~579 | ~162 |
| Hazelnuts | ~628 | ~176 |
| Walnuts | ~654 | ~183 |
| Pecans | ~691 | ~193 |
| Macadamias | ~718 | ~201 |
Preparation and moisture shift the exact number. Still, the roughly 158-calorie gap between pistachios and macadamias per 100 g becomes only about 44 calories per ounce.
Chestnuts are nutritionally an outlier
Roasted chestnuts can land around 200–250 calories per 100 g with only a few grams of fat. Macadamias are about 718 calories and 76 g fat per 100 g. That is a difference of more than 450 calories per 100 g.
So “chestnuts are the lowest-calorie nut” is true, but not always the comparison someone intends when choosing among almonds, walnuts, pistachios, and other high-fat nuts.
Among fatty nuts, the differences are much smaller
Cashews and pistachios sit around 550–560 calories per 100 g; almonds are around 579. One ounce of pistachios and one ounce of almonds differ by only about 5 calories.
Serving size changes the practical result
One ounce of pistachios is roughly 157 calories; two ounces are about 314. That 157-calorie increase from portion size is much larger than the difference between many nut types.
Per-100-g values are excellent for standardized comparison. They are not a suggestion that 100 g is the appropriate serving.
Lower calorie does not automatically mean nutritionally better
Walnuts are about 654 calories/100 g versus roughly 560 for pistachios, but walnuts also stand out for ALA omega-3. Almonds and pistachios bring different combinations of fiber, vitamin E, magnesium, protein, and potassium.
How to compare nuts without letting calorie tables mislead you
Chestnuts sit apart because they contain far less fat than the nuts people usually snack on by the handful. Once chestnuts are removed from the comparison, the calorie differences among almonds, pistachios, cashews, walnuts, pecans, hazelnuts, and macadamias become much less dramatic in a normal serving. A gap that looks large per 100 grams can shrink to a modest difference per ounce. For someone trying to manage energy intake, weighing or portioning a serving is often more useful than switching repeatedly between nuts based on a small ranking advantage.
Preparation can matter as well. Dry-roasted nuts may remain close to raw nuts in energy density, while oil-roasted versions can pick up additional fat depending on the process. Sweet coatings, chocolate, honey, or sugar can move the calorie count further, and salted products change sodium rather than calories in a major way. Nut butters deserve the same portion awareness because they are easy to eat quickly and do not look like a large volume of food even when they contain the equivalent of many nuts.
Calories are only one reason to choose a nut. Different varieties provide different balances of unsaturated fats, protein, fiber, minerals, and other plant compounds. Walnuts are notable for plant omega-3 ALA, almonds are commonly valued for vitamin E, and several nuts contribute magnesium and other minerals. That means the lowest-calorie option is not automatically the most useful choice for every diet. A person may reasonably prefer a slightly higher-calorie nut because it fits a nutrient goal, a recipe, or simply makes a portion more satisfying.
The most practical strategy is to separate two questions: “Which nut is lowest in calories?” and “Which nut works best for this snack or meal?” Chestnuts answer the first question clearly, but for ordinary fatty nuts, portion size usually dominates the difference. Choosing a small, deliberate serving of a nut you enjoy can be easier to sustain than chasing the lowest number while ignoring taste, texture, and how the food is actually eaten.
Buying format can quietly determine how many calories are eaten. Nuts taken from a large open bag are easy to pour generously, whereas a small bowl or pre-portioned container makes the serving visible. Chopped nuts spread flavor through oatmeal, yogurt, salads, or vegetables with less quantity than eating them as a standalone handful. Chestnuts, meanwhile, are used more like a starchy seasonal food than a concentrated nut snack. That difference in eating pattern is one reason their low calorie density should not be interpreted as evidence that every recipe should substitute chestnuts for other nuts.
The useful takeaway
Chestnuts are clearly the lowest-calorie option but are a different nutritional case. Among typical fatty nuts, cashews and pistachios are near the lower end. Once you compare realistic one-ounce servings, however, many of the calorie differences become fairly small.
Sources
- USDA FoodData Central — Food composition per 100 g and variation by food form, preparation, and product.