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    Biological efficiency calculator

    Biological efficiency (BE) is the fresh weight of every flush from a block divided by the block's dry substrate weight, times 100. Enter your harvest and your block. If you only know what the block weighed wet, the calculator takes the water out first.

    Biological efficiency calculator

    lb

    Weigh each flush right after picking, before you mist, and add them up.

    What do you know about the block?
    lb
    %

    Sawdust blocks are usually mixed to 55–67% water.

    Biological efficiency

    74.9%

    • 1.31 lb fresh ÷ 1.75 lb dry substrate × 100
    • Dry substrate: 5 lb × (1 − 65%) = 1.75 lb

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    How does the biological efficiency calculator work?

    • BE (%) = total fresh weight of all flushes ÷ dry substrate weight × 100
    • Dry substrate weight = wet block weight × (1 − moisture)

    For example: A 5-lb block mixed to 65% moisture holds 5 × (1 − 0.65) = 1.75 lb of dry substrate. If its flushes add up to 1.31 lb of fresh mushrooms, its BE is 1.31 ÷ 1.75 × 100, about 75%.

    • BE can pass 100% because fresh mushrooms are mostly water, while the substrate is weighed dry.
    • If you don't know a kit's moisture, sawdust blocks are usually mixed to 55–67% water, so the dry weight is roughly 33–45% of what the block weighs. Run both ends for a range, and treat it as a ballpark that runs high.
    • Use one unit for both weights. A block lost before it fruits scores 0%, so leave it out of your BE average.

    Where do the numbers come from?

    Every formula and figure on this page is from one of our grower guides, which cite their sources: extension services, farm trials and published studies.

    Common questions

    What is a good biological efficiency?

    It depends on the species. A UC Cooperative Extension guide gives oysters 100–200%, shiitake 50–145% and maitake 5–35%. Farm figures run lower than lab ones: five farms in a USDA SARE study averaged 0.88 lb per 5-lb block started, about 50% BE with lost blocks counted. Our biological efficiency guide lists published figures by species.

    Can biological efficiency be over 100%?

    Yes. Fresh mushrooms are mostly water, about 91% for oysters and 85% for shiitake in a UC Cooperative Extension deck, and the substrate is weighed dry. So a block can give more fresh weight than its dry weight.

    Does the spawn count in the dry substrate weight?

    We found no source that settles it. One oyster study divides by the dry substrate per bag before inoculation, which reads as leaving the spawn out. Pick one rule and keep it, so your own blocks compare fairly.

    Where does Hypha come in?

    Hypha doesn't calculate biological efficiency, and it has no dry substrate weight field. It keeps the harvest side: log each flush's fresh weight on a block, and the Grow Summary shows the block's total harvest. Write the block's dry substrate weight in its notes, then bring both numbers here when the block is finished. Flush logging is on the free plan.

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