Mycelocity
Biological efficiency, or BE, is the single most-quoted number in mushroom cultivation — and one of the most misread. It is the ratio of fresh mushroom yield to the dry weight of the substrate, expressed as a percentage:
BE 100% means one kilogram of dry substrate produced one kilogram of fresh mushrooms.
Because fresh mushrooms are roughly 90% water, a BE of 100% is genuinely strong performance, not a break-even point. It is normal — and profitable — to run well below 100%.
Why dry weight, not wet weight
BE is pinned to dry substrate weight precisely because moisture is so variable. Two growers could load identical bags of supplemented sawdust at very different hydration levels; quoting yield against wet weight would make the wetter bag look more “efficient” when nothing biological changed. Dry weight strips moisture out of the comparison so BE reflects how well the mycelium actually converted nutrition into fruit.
This is why hydration and BE travel together. Use the Substrate Moisture & Hydration calculator to recover dry weight from a wet sample, then feed that dry weight into the Biological Efficiency calculator.
Typical BE ranges by species
BE is species- and technique-dependent. As rough working figures:
- Oyster — 75–100%+, fast and forgiving
- Shiitake — 50–75%, slower but premium
- Lion’s Mane — 50–65%, sensitive to fruiting conditions
- King Oyster — 55–70%, fewer but heavier fruits
These are the defaults baked into the species presets. Treat them as a starting point and replace them with your own measured numbers as soon as you have a few flushes logged.
Flush distribution
Total yield does not arrive at once. Most of it comes in the first flush, with diminishing returns after that — a common pattern is something like 60% / 30% / 10% across three flushes. Knowing this matters for cash flow and labour planning: you harvest the bulk early, then decide whether the later, smaller flushes are worth the chamber time.
Putting it to work
- Weigh and dry-correct your substrate (see the hydration guide).
- Enter your dry weight and a realistic BE into the calculator.
- Read fresh yield per block in grams and pounds, split by flush.
- That per-block yield then flows into contamination, revenue and capacity downstream — it is the root of the whole model.
If your real-world yield consistently undershoots the BE you entered, the usual culprits are hydration, contamination losses, or fruiting conditions — not the formula. The next two guides cover the first two directly.