Mushrooms are one of the lowest-calorie foods you can add to a meal, but “calories per slice” is surprisingly variable. A thin mushroom slice can weigh under a gram, while a thick portobello slice can weigh 3 grams or more. This mushroom calories per slice calculator estimates calories using the specific variety and slice weight you choose.
Select a mushroom type, enter your number of slices, and set an approximate grams-per-slice value. The calculator then shows total calories, calories per slice, and a macro breakdown for your portion.
It is a handy tool for anyone tracking calories, building a salad, topping a pizza, filling an omelet, or writing a recipe with fresh mushroom ingredients.
🍄 Mushroom Calories Per Slice
Estimate calories and macros for fresh, raw mushrooms sliced your way.
Quick Start
To get a calorie estimate, start with the number of slices you plan to use, then choose the mushroom variety from the dropdown. Next, set a grams-per-slice value. Thin slices from small button mushrooms typically weigh about 1 g, medium slices often weigh 2 g, and thick slices or larger portobello slices can reach 3 g or more. If you have a food scale, weigh ten typical slices and divide by ten for a more accurate average instead of guessing. Press Calculate calories to view the total calories, the per-slice value, and the carbohydrate, protein, and fat totals for the whole portion.
How the Math Works
The engine behind this tool is simple proportional scaling. Every raw mushroom variety has published nutrition values per 100 g. If a variety supplies 22 kcal per 100 g, then a 1 g slice supplies 0.22 kcal. Multiply by your actual grams per slice and by the number of slices to get the full portion.
Total calories = calories per slice × number of slices.
The same scaling applies to carbohydrates, protein, and fat. Because raw mushrooms are roughly 90% water, the numbers per slice are small, but they accumulate quickly when you add 20–30 slices to a pizza, sandwich, or stir-fry.
Worked Examples
Example 1: 12 slices of white button mushroom at 2 g per slice. White button mushrooms have about 22 kcal/100 g, so each slice is 0.44 kcal and the whole portion is about 5.3 kcal. The macros are roughly 0.8 g carbs, 0.7 g protein, and 0.1 g fat.
Example 2: 6 fresh shiitake slices at 2.5 g per slice. Shiitake has about 34 kcal/100 g, so one slice is about 0.85 kcal and the six-slice portion comes to about 5.1 kcal.
Example 3: 8 portobello slices at 3 g per slice. At 22 kcal/100 g, each thick slice is 0.66 kcal, giving a total of about 5.3 kcal. This shows how similar the calorie counts are across different varieties when the portion size is comparable.
Why Slice Weight Varies
Two people slicing the same mushroom can end up with very different counts. A mushroom sliced thinly with a mandoline can produce slices under 1 g, while a thick hand-cut slice may weigh 3 g. Slice orientation also matters: slicing a large portobello cap across its curve versus along the stem produces different surface areas, which changes slice weight. The purpose of this calculator is not laboratory precision but practical consistency. If you always use the same knife and thickness, your daily tracking will be repeatable and reliable enough for meal planning.
Reference Values
The table lists approximate nutrition values per 100 g of raw fresh mushrooms, based on USDA FoodData Central. Actual values vary slightly by growing conditions, maturity, and moisture content.
| Variety | kcal | Carbs | Protein | Fat |
|---|---|---|---|---|
| White button / cremini | 22 | 3.3 g | 3.1 g | 0.3 g |
| Portobello, fresh | 22 | 3.9 g | 3.1 g | 0.3 g |
| Shiitake, fresh | 34 | 6.8 g | 2.2 g | 0.5 g |
| Oyster, fresh | 33 | 6.1 g | 3.3 g | 0.4 g |
| Enoki, fresh | 37 | 7.8 g | 2.7 g | 0.3 g |
Data source: USDA FoodData Central.
Accuracy and Limitations
Natural variability in fresh mushrooms can shift calorie values by roughly 10–20% in either direction, so treat the result as an estimate rather than an exact figure. This tool assumes raw mushrooms with no added oil, butter, or marinade. Cooking mushrooms without added fat changes their water content and concentration but not their total calories. If you sauté mushrooms in oil or butter, the added fat can contribute far more calories than the mushrooms themselves.
Tips for Consistent Tracking
- Weigh a handful of your actual slices on a kitchen scale to find a realistic grams-per-slice average instead of guessing.
- Write down the preset you use, such as “thin, 1 g” or “thick, 3 g”, so your future entries stay consistent.
- If you do not have a scale, use this rule of thumb: 1 g for delicate thin slices, 2 g for standard medium slices, and 3 g for thick chunks or large portobello slices.
- For mixed-mushroom recipes, calculate each variety separately and add the totals, since enoki and shiitake have noticeably higher calorie densities than button mushrooms.
Frequently Asked Questions
Do mushrooms have more calories when cooked? The mushrooms themselves do not gain calories from heating, but cooking in oil, butter, or a rich sauce adds fat and calories. Re-weigh after cooking and choose a cooked-food entry if you add fats.
Why does per-slice calorie count matter? For such a low-calorie food, tracking by slice is a convenient shorthand when a food scale is not available. The estimate is accurate enough for most meal planning, and it helps you compare portion sizes visually.
Can I use this for canned or dried mushrooms? Not directly. Canned mushrooms have different water and sodium content, while dried mushrooms are much more calorie-dense by weight. This calculator is designed for fresh, raw slices only.