Mushroom Growing Calculators
Free, no-signup calculators for gourmet and culinary mushroom cultivation. Each one shows the formula it uses and a worked example, so you can check the maths rather than trust a black box.
Biological Efficiency (BE) Calculator
Compare how much fresh mushroom a block returned against the dry substrate that went into it.
Open calculatorSpawn to Substrate Ratio Calculator
Work out spawn weight for a bulk substrate batch at your chosen ratio.
Open calculatorSubstrate Hydration Calculator
Mass-balance water calculation for hydrating coir, pellets, straw or soy hulls.
Open calculatorMushroom Growing Equipment Checklist
Pick your workflow and get a printable list of what is essential, useful and optional.
Open calculatorMushroom Fruiting Air Exchange Calculator
Size fresh-air ventilation for a fruiting chamber in CFM and m³/h from its dimensions.
Open calculatorMushroom Contamination Checker
Answer a few questions about what you can see and get cautious next steps. Not a diagnosis.
Open calculatorMaster's Mix Mushroom Substrate Calculator
Batch maths for 50:50 hardwood and soy hull substrate — per block and per batch.
Open calculatorMushroom Grow Bag Calculator
Scale a hydrated production block recipe across a whole batch of grow bags.
Open calculatorMushroom Substrate Selector
What should I grow it on? Choose a species and grow style for a sensible substrate starting point.
Open calculatorWant the numbers kept for you? Hyphae Fidelity is a free grow tracker that records every batch, check and harvest so figures like these come straight from your own logs.
How these calculators fit together
Most gourmet mushroom grows follow roughly the same sequence, and each calculator above covers one link in that chain. Start with a substrate choice suited to your species and grow style — straw for oysters, supplemented hardwood for lion's mane or shiitake. From there, use the hydration calculator (or the dedicated Master's Mix calculator for a 50:50 hardwood-and-soy-hull recipe) to work out how much water your dry ingredients need before mixing.
Once the substrate is hydrated and pasteurised or sterilised, the spawn ratio calculator tells you how much grain spawn to add for a given batch weight, or use the grow bag calculator to scale a whole recipe across a production run of bags. During colonisation, keep an eye on conditions with the contamination checker if anything looks off, and use the equipment checklist to make sure you have what your workflow needs.
Moving into fruiting, the fruiting air exchange calculator sizes the fresh-air ventilation a tent or room needs for its volume. Finally, once you have harvested, the biological efficiency calculator compares your fresh harvest weight against the dry substrate that went in, which is the standard way to judge how a batch actually performed and to compare recipes or species over time.
Each calculator links out to a paired explanatory guide in our full library of growing guides. If you are starting from scratch, the beginner's guide to growing mushrooms at home in the UK walks through the whole process end to end, with links back to the relevant calculator at each stage. Running a website of your own? You can embed any of these calculators directly on your own pages, free, with attribution.