Mushroom Biological Efficiency Calculator
Biological efficiency (BE) compares the fresh mushrooms a block produced against the dry weight of the substrate ingredients it was made from. Add each flush as you harvest it to see your running yield and BE %.
Learn the method behind this calculatorBE % = total fresh harvest weight ÷ dry substrate ingredient weight × 100
The denominator is the weight of your dry ingredients before water was added — not the hydrated block weight. Using the wet block weight makes BE look far lower than it is.
The combined dry weight of sawdust, hulls, straw, coir and any supplement, weighed before hydrating. Must be greater than zero.
Gourmet and culinary species only. This only labels your result — it does not change the maths.
Enter your dry substrate weight and at least one flush to see the biological efficiency.
What biological efficiency means
Biological efficiency is the standard way growers express mushroom yield relative to the substrate that produced it. Because fresh mushrooms are mostly water and dry substrate is not, a BE of 100% does not mean the fungus converted everything it was given — it simply means the block returned a fresh weight equal to its dry substrate weight. It is a comparison ratio, and it is only meaningful when everyone measures it the same way.
Worked example
A block is made from 1,000 g of dry ingredients — 800 g hardwood sawdust and 200 g soy hulls — then hydrated to around 2.5 kg. It produces 450 g on the first flush and 300 g on the second, so 750 g fresh in total. BE = 750 ÷ 1,000 × 100 = 75%. Note the denominator is 1,000 g, not the 2.5 kg hydrated block.
Why dry substrate weight is the denominator
Hydrated blocks vary enormously — the same recipe at 55% moisture and at 65% moisture gives very different wet weights from identical dry ingredients. Dividing by the wet weight would make your BE swing with how much water you happened to add, which tells you nothing about the grow. Dry ingredient weight is stable and repeatable, so it is what the industry uses. Weigh your ingredients dry, write the number on the bag, and you can compare every block you ever make.
Comparing grows fairly
- Count the same number of flushes in every block you compare.
- Weigh fresh, at the same point in development, on the same scales.
- Record the recipe, moisture target, spawn rate and species alongside the number.
- Change one thing at a time between batches, otherwise you cannot tell what caused a difference.
Frequently asked questions
Is this the same as a mushroom yield calculator?
Yes — it gives your total fresh yield and expresses it as a percentage of the dry substrate, which is how growers compare yields between blocks, recipes and species.
Should I use dried mushroom weight?
No. Standard BE uses fresh mushroom weight over dry substrate weight. Mixing dry over dry is a different measure and is not comparable to published figures.
What counts as a good BE?
There is no single answer, and we would rather not invent one. Reported figures vary widely by species, substrate, supplementation and how many flushes are counted. Use your own history as the baseline.
Do I include the supplement in the dry weight?
Yes — include every dry ingredient that went into the substrate, including bran or soy hull supplements. Do not include the water, the bag or the grain spawn unless you state that you are doing so.
Related calculators
- Grow bag / production block calculator — work out the dry ingredient weight this calculator needs.
- Master's Mix calculator — hardwood and soy hull batches.
- Spawn ratio calculator — spawn weight for a bulk substrate batch.
Track each flush in Hyphae Fidelity
Hyphae Fidelity is a free grow tracker for gourmet cultivation — log every batch, check, harvest and contamination, and see what actually works in your setup.