Mushrooms are one of the lowest-calorie foods you can eat. Most common varieties contain just 22 to 33 calories per 100 grams raw, which is roughly one cup of sliced mushrooms. That makes them lighter than almost any other whole food you’d put on a plate.
Calories by Mushroom Variety
Not all mushrooms are identical, but the calorie differences between varieties are small. Here’s what you get per 100 grams (about 3.5 ounces) raw:
- White button: 22 calories, 3.1g protein, 3.3g carbs, 0.3g fat
- Cremini (baby bella): 22 calories, 2.5g protein, 4.3g carbs, 0.1g fat
- Portobello: 22 calories, 2.1g protein, 3.9g carbs, 0.4g fat
- Morel: 31 calories, 3.1g protein, 5.1g carbs, 0.6g fat
- Maitake: 31 calories, 1.9g protein, 7g carbs, 0.2g fat
- Oyster: 33 calories, 3.3g protein, 6.1g carbs, 0.4g fat
White button, cremini, and portobello mushrooms are actually all the same species picked at different growth stages, which is why their calorie counts are nearly identical. Oyster and maitake mushrooms run slightly higher but still clock in under 35 calories per 100 grams. For practical purposes, you can treat any common mushroom as roughly 20 to 30 calories per cup.
Why Mushrooms Are So Low in Calories
Mushrooms are roughly 90% water by weight. Raw samples range from about 67% to 92% moisture depending on the variety. That water content means very little room for calorie-dense macronutrients. What remains is mostly a small amount of carbohydrate and protein, with virtually no fat. A full cup of sliced white mushrooms has fewer calories than a single tablespoon of olive oil.
Despite the low calorie count, mushrooms do contain meaningful fiber. Oyster mushrooms provide 2.3 grams per 100 grams, morels 2.8 grams, and maitake 2.7 grams. Mushroom fiber includes beta-glucans, a type of soluble fiber that can help you feel full longer.
How Cooking Changes the Numbers
When you cook mushrooms, they lose water and shrink. On average, 100 grams of raw mushrooms yield about 77 grams cooked. That means the cooked portion is more calorie-dense per gram, not because calories were added, but because water evaporated and the mushroom concentrated.
If you start with 100 grams of raw white button mushrooms (22 calories) and cook them in a dry pan, you’ll end up with roughly 77 grams that still contain 22 calories. The calorie count per gram goes up slightly, but the total stays the same. The real variable is cooking fat. A tablespoon of butter or oil adds 100 to 120 calories, which can easily quadruple the calorie content of a mushroom dish. If you’re tracking calories closely, sautéing in a small amount of broth or using a nonstick pan keeps things lean.
Micronutrients Worth Knowing About
Mushrooms punch well above their calorie weight when it comes to nutrients. Potassium is one standout: white button mushrooms contain 358 mg per 100 grams, comparable to a small banana. Oyster mushrooms provide 324 mg, and enoki mushrooms hit 359 mg.
B vitamins are another strength. Mushrooms are a solid source of niacin, with enoki providing 7 mg per 100 grams (nearly half the daily recommended intake of 16 mg). Oyster mushrooms deliver close to 6 mg. Riboflavin, pantothenic acid, and folate are also present in meaningful amounts across most varieties.
The Vitamin D Advantage
Mushrooms are the only non-animal whole food that naturally produces vitamin D, and they can produce a lot more with UV light exposure. Standard portobello mushrooms contain just 11 IU of vitamin D per 100 grams, which is negligible. But portobellos exposed to UV light for 15 to 20 seconds jump to around 446 IU per 100 grams. Some producers achieve even higher levels: USDA testing found UV-treated portobello samples ranging from 140 to 753 IU per 100 grams depending on the producer. One maitake mushroom producer using a proprietary UV method reached 2,242 IU per 100 grams.
Look for packaging that says “UV-treated” or “high in vitamin D” if this matters to you. You can also place store-bought mushrooms gill-side up in direct sunlight for 15 to 30 minutes to boost their vitamin D content yourself.
Mushrooms as a Meat Substitute for Fewer Calories
One of the most practical uses of mushrooms in a lower-calorie diet is swapping them in for ground meat. A cup of cooked ground beef contains roughly 230 to 300 calories. The same volume of cooked mushrooms has about 30 to 40 calories before any added fat. Even a partial swap makes a dent.
A year-long randomized clinical trial tested this directly, having participants replace meat with mushrooms in their regular meals. By the end of the study, those on the mushroom diet consumed an average of 123 fewer calories per day compared to participants eating their standard diet. That kind of modest daily reduction, sustained over months, is the type that leads to gradual weight change without the feeling of restriction. Mushrooms work well here because their texture is meaty and satisfying, especially portobellos, cremini, and oyster varieties.
Quick Calorie Reference by Serving
Since most people don’t weigh their mushrooms on a kitchen scale, here are some practical estimates:
- 1 cup sliced raw mushrooms (about 70g): 15 calories
- 1 medium whole white button mushroom (about 18g): 4 calories
- 1 whole portobello cap (about 85g): 19 calories
- 1 cup cooked mushrooms, no added fat (about 155g): 44 calories
These numbers are low enough that mushrooms are often considered a “free” food in many dietary plans. You can add them generously to omelets, stir-fries, salads, soups, and grain bowls without meaningfully changing the calorie total of the meal.