In this article, I’ve put together an ultimate guide with charts so you can quickly work out the exact weights and calories of various portions and types of edible mushrooms.
I’ve also done research into how much mushrooms shrink during the cooking process and I’ve recorded my findings below.
Button (Closed Cup) Mushroom Weights
The most common variety of mushrooms which we eat is the button or closed cup mushroom and these are widely available in stores and supermarkets.
Button mushrooms are the smaller version of an open cup flat mushroom which have not been allowed to grow open and flat. They are also sold as ‘baby’ mushrooms and these simply button mushrooms which are picked early when they’re very small.
I did some research and weighed a large selection of raw baby button mushrooms along with mixed-sized standard button mushrooms to get some average weights and found the following.
A baby button mushroom weighs around 5-10g/0.18-0.35oz, a medium-sized button mushroom weighs around 20-25g/0.7-0.88oz and a large button mushroom weighs around 50-60g/1.76-2.12oz.
Use the chart below to find the weight conversions for various sizes of button (closed cup) mushrooms:
| Small (baby) button mushroom weight | Medium button mushroom weight | Large button mushroom weight |
| 5-10g | 20-25g | 50-60g |
| 0.18-0.35oz | 0.7-0.88oz | 1.76-2.12oz |
| 0.005-0.01kg | 0.02-0.025kg | 0.05-0.06kg |
| 0.01-0.02lb | 0.04-0.06lb | 0.1-0.13lb |
Flat Mushroom (Open Cup) Weights
A large flat mushroom is the same as a button mushroom, but it’s been allowed to grow to a bigger size and has opened out, which is something mushrooms do before they spore.
Large flat mushrooms are the most common type of large mushroom and are becoming increasingly popular in vegan and vegetarian dishes.
I weighed a number of raw flat mushrooms that were bought from a supermarket to get an average weight and the results were as follows:
An average medium-sized flat (open cup) white mushroom weighs around 60-70g/2.12-2.5oz, smaller flat mushrooms weigh around 50-60g/1.76-2.12oz and large flat mushrooms weigh 70g/2.5oz plus.
Use the chart below to find the weight conversions for various sizes of flat white (open cup) mushrooms:
| Small flat white mushroom weight | Medium flat white mushroom weight | Large flat white mushroom weight |
| 50-60g | 60-70g | 70g plus |
| 1.76-2.12oz | 2.12-2.5oz | 2.5oz plus |
| 0.05-0.06kg | 0.06-0.07kg | 0.07kg plus |
| 0.01-0.13lb | 0.13-0.15lb | 0.15lb plus |
Flat Portobello Mushroom Weights
Like flat white mushrooms, Portobello mushrooms are open cup mushrooms that have been allowed to grow to a bigger size and open out.
Portobello mushrooms are also known as brown mushrooms and can be cooked in the same way as a large flat white mushroom.
An average medium-sized flat (open cup) Portobello (or brown) mushroom weighs around 60-70g/2.12-2.5oz, smaller flat mushrooms weigh around 50-60g/1.76-2.12oz and large flat mushrooms weigh 70g/2.5oz plus.
Use the chart below to find the weight conversions for various sizes of flat Portobello/brown (open cup) mushrooms:
| Small flat Portobello/brown mushroom weight | Medium flat Portobello/brown mushroom weight | Large flat Portobello/brown mushroom weight |
| 50-60g | 60-70g | 70g plus |
| 1.76-2.12oz | 2.12-2.5oz | 2.5oz plus |
| 0.05-0.06kg | 0.06-0.07kg | 0.07kg plus |
| 0.01-0.13lb | 0.13-0.15lb | 0.15lb plus |
Chestnut (Brown) Mushroom Weights
Chestnut or brown mushrooms are similar to button mushrooms, but they have a nutter flavor and a brown outer skin.
Chestnut mushrooms are closed cup and have not grown enough that they’ve started to open out to become a ‘flat mushroom’.
I did some research and weighed a large selection of mixed-sized closed cup chestnut (or brown) mushrooms to get some average weights and found the following:
A small chestnut mushroom weighs around 5-10g/0.18-0.35oz, a medium-sized chestnut mushroom weighs around 10-20g/0.35-0.71oz and a large button mushroom weighs around 20-40g/0.71-0.09oz.
Use the chart below to find the weight conversions for various sizes of chestnut (or brown) mushrooms:
| Small (baby) button mushroom weight | Medium button mushroom weight | Large button mushroom weight |
| 5-10g | 10-20g | 20-40g |
| 0.18-0.35oz | 0.35-0.71oz | 0.71-0.09oz |
| 0.005-0.01kg | 0.01-0.02kg | 0.02-0.04kg |
| 0.01-0.02lb | 0.02-0.04lb | 0.04-0.01lb |
Oyster Mushroom Weights
Oyster mushrooms come in various sizes and are generally sold in a cluster because they grow on one main stalk.
The average weight of a cluster of oyster mushrooms when they’re sold in a cluster is 150g/5.29oz.
How Much Do Mushrooms Shrink When Cooked?
If you’ve ever cooked any variety of mushrooms, you’ll know that they shrink in size quite considerably during the cooking process.
It’s useful to know how mush foods shrink while cooking if you’re trying to work out portion sizes for recipe planning or for calorie counting.
I did research and cooked ordinary white button mushrooms in only their ow juices to see how much they weighed after cooking and here are the results:
I cooked 200g of sliced button mushrooms in a pan and gently sweated them down in their own juices until they’d shrunk down and once drained the mushrooms weighed 150g. This was a reduction of 25% of the original raw mushroom weight.
To work out how much your portion of mushroom will shrink during cooking, use this simple equation:
Raw mushroom weight minus 25% = cooked mushroom weight
How Many Mushrooms are in a Serving?
A serving of mushrooms is equal to one cup or 70g/2.5oz of raw chopped mushroom of any type.
A serving of this size contains 15 calories (in kcal) and will reduce in weight to around 53g/1.87oz when cooked and drained.
Mushroom Weight and Calorie Chart
Use the chart below to find more mushroom serving weights and calories, these figures are based on generic raw mushroom types and should work for all varieties.
Button mushroom weights use an assumption of an average medium mushroom weighing 20g/0.7oz each and for flat mushrooms, I’ve used an averaged medium-sized mushroom weight of 60g/2.12oz.
| Mushroom Serving Size | Average Raw Weight | Calories (in kcal) |
| 1 average button mushroom | 20g/0.71oz | 4 |
| 2 average button mushrooms | 40g/1.41oz | 9 |
| 3 average button mushrooms | 60g/2.12oz | 13 |
| 4 average button mushrooms | 80g/2.82oz | 18 |
| 5 average button mushrooms | 100g/3.53oz | 22 |
| 6 average button mushrooms | 120g/4.23oz | 26 |
| 7 average button mushrooms | 140g/4.94oz | 31 |
| 8 average button mushrooms | 160g/5.64oz | 35 |
| 9 average button mushrooms | 180g/6.35oz | 39 |
| 10 average button mushrooms | 200g/0.71oz | 44 |
| 1 average flat mushroom | 60g/2.12oz | 13 |
| 2 average flat mushrooms | 120g/4.23oz | 26 |
| 3 average flat mushrooms | 180g/6.35oz | 39 |
| 4 average flat mushrooms | 240g/8.47oz | 53 |
| 5 average flat mushrooms | 300g/10.58oz | 66 |
| 6 average flat mushrooms | 360g/12.7oz | 79 |
| 7 average flat mushrooms | 420g/14.82oz | 92 |
| 8 average flat mushrooms | 480g/16.93oz | 105 |
| 9 average flat mushrooms | 540g/19.05oz | 118 |
| 10 average flat mushrooms | 600g/21.16oz | 131 |
| 25g of mushroom | 25g/0.88oz | 5 |
| 50g of mushroom | 50g/1.76oz | 11 |
| 75g of mushroom | 75g/2.65oz | 16 |
| 100g of mushroom | 100g/3.53oz | 22 |
| 1oz of mushroom | 28g/1oz | 6 |
| 2oz of mushroom | 57g/2oz | 12 |
| 3oz of mushroom | 85g/3oz | 19 |
| 4oz of mushroom | 113g/4oz | 25 |
More Mushroom Weight FAQs
Based on an average medium-sized button mushroom weighing around 20g/0.71oz, there are around 5 average-sized button (or closed cup) mushrooms in 100g.
Based on an average medium-sized button mushroom weighing around 20g/0.71oz, there are around 23 average-sized button (or closed cup) mushrooms in a pound.
Based on an average medium-sized button mushroom weighing around 20g/0.71oz, there are around 50 average-sized button (or closed cup) mushrooms in a kilogram.
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