Calculate spawn, substrate, and water needed for your mushroom grow — then see expected yield per flush, total harvest across all flushes, and annualized production. Covers oyster, shiitake, lion's mane, king oyster, and reishi in bags, logs, or buckets.
Biological efficiency (BE) is the ratio of fresh mushroom weight harvested to the dry weight of the substrate used, expressed as a percentage. If you start with 5 lbs of dry hardwood sawdust and harvest 5 lbs of fresh oyster mushrooms across all flushes, your BE is 100%. This is the standard metric in commercial mushroom cultivation, and it's the calculation this calculator uses under the hood.
Oyster mushrooms on hardwood sawdust or supplemented blocks regularly hit 75–100% BE in a home or small farm setting, which is why they're the most popular beginner species — the economics are simply favorable. Shiitake runs lower, typically 40–60% BE on hardwood sawdust bags and 30–50% on logs over their productive lifespan. Lion's mane achieves 50–70% on sawdust. Reishi is a medicinal species with low culinary yield; it's grown for dried fruiting bodies and won't make economic sense as fresh food at typical growing scales.
Master's Mix — a 50/50 blend of hardwood fuel pellets (HWFP) and soy hulls — was developed by the commercial cultivation community to push BE higher, and it delivers roughly a 20% improvement over plain sawdust for most species. The tradeoff is that Master's Mix is "hot" and nutrient-dense enough to require full sterilization (15 PSI for 2.5+ hours) rather than pasteurization — skipping sterilization on Master's Mix almost guarantees contamination from Trichoderma and other competitor molds. Straw is the opposite: low-nutrient, easy to pasteurize with boiling water or a lime-bath soak, but it only works well for oyster mushrooms and produces lower total yield than sawdust.
This is the single most important contamination-prevention decision in substrate preparation. Pasteurization heats substrate to 160–185°F for 1–2 hours. This kills most competing molds and bacteria but leaves heat-resistant endospores alive. It works fine for straw and coffee grounds because those substrates are low enough in nutrients that fast-colonizing oyster spawn outcompetes whatever wakes up from the endospores. For hardwood sawdust, pasteurization is sometimes adequate — many growers use the "field capacity" cold water lime soak (raising pH to 12 kills most competitors) — but sterilization gives more reliable results.
Sterilization uses a pressure cooker or autoclave at 15 PSI (250°F) for 2.5–3 hours, which kills endospores. It's required for any substrate supplemented with nitrogen sources (bran, soy hulls, cottonseed meal), for Master's Mix, and for any grain spawn master culture work. Without sterilization on high-nutrient substrate, Trichoderma (green mold) will colonize the block before your mycelium can. Once green mold appears in a block, there is no recovery — the block is finished and should be removed from your grow space to prevent spore spread.
Practical contamination prevention breaks down to: correct hydration (field capacity — a handful squeezed hard should drip just 1–2 drops, not stream), thorough sterilization or pasteurization appropriate to your substrate, inoculation in still air or under a still air box or laminar flow hood, clean spawn with no visible contamination before use, and maintaining humidity and fresh air exchange during fruiting without creating stagnant wet air that promotes mold. The biggest single beginner mistake after contaminated substrate is excess moisture sitting on fruiting surfaces — wipe condensation off your tent walls and keep air moving.
Oyster (Pleurotus ostreatus, P. pulmonarius, P. eryngii): 55–75°F for blue/pearl oyster; 70–85°F for pink and yellow oyster. Humidity 85–95%. High CO2 tolerance during colonization but fruiting requires fresh air exchange — elevated CO2 causes elongated stems and stunted caps. Fruiting is triggered by a temperature drop, high humidity, and light (indirect, ambient light is fine). Pin sets appear quickly — oyster can go from pinning to harvest-ready in 3–7 days at warm temperatures.
Shiitake (Lentinula edodes): 55–75°F for fruiting. Blocks require a "cold shock" trigger — soak the colonized block in cold water (50–60°F) for 8–24 hours. This mimics seasonal rain and temperature changes that trigger natural fruiting. Log-grown shiitake are dunked in cold water for 24 hours to trigger fruiting cycles. Shiitake is slower to colonize than oyster (3–8 weeks on blocks, 6–18 months on logs) but the resulting mushrooms command higher market prices and have a longer shelf life when properly dried.
Lion's Mane (Hericium erinaceus): 65–75°F. Humidity 85–95%. Very sensitive to CO2 — high CO2 causes the signature "teeth" to elongate into icicle-like formations rather than the dense pom-pom shape that sells at market. Keep fresh air exchange high during fruiting. Lion's mane is one of the fastest-growing mushrooms from pinning to harvest and is extremely popular at farmers markets for its culinary and medicinal reputation, but it's also the most contamination-sensitive species on this list.
King Oyster / Trumpet (Pleurotus eryngii): 55–65°F for fruiting — the coolest of the common gourmet species. It grows slowly and produces thick, meaty stems with small caps that have an excellent shelf life compared to other oysters. King oyster performs best in bags without side holes — the substrate block is exposed from the top and fruiting bodies push up vertically, developing the characteristic elongated stem. CO2 management matters here too: elevated CO2 encourages longer stems (which some markets prefer) while higher FAE produces fatter, shorter mushrooms.
Reishi (Ganoderma lucidum): 70–80°F. Long colonization time (4–8 weeks). Fruiting bodies develop slowly over 3–5 months and are harvested dried. Unlike the species above, reishi is not harvested fresh — the woody fruiting bodies are dried and used for tea, tincture, or powdered supplements. Yield by fresh weight is low but market price for quality dried reishi is high. Antler-form reishi (elevated CO2) vs. cap-form reishi (full FAE) — antler form is often preferred for aesthetics and is easier to achieve in a controlled environment.
Bag/block cultivation is the fast-return method. You can inoculate a 5 lb sawdust block today and be harvesting mushrooms in 4–6 weeks. Blocks are completely controllable — you manage temperature, humidity, and fruiting timing. The downsides are upfront investment in a pressure cooker (or purchasing pre-sterilized blocks), the need for clean inoculation technique, and the limited productive lifespan of each block (typically 2–4 months before the substrate is exhausted). For commercial production at any scale, bags and blocks are the standard.
Log cultivation is the long-game method. You drill holes in a freshly cut hardwood log (oak, maple, and alder work best), hammer in wooden plug spawn, seal the holes with cheese wax, and wait. The logs colonize over 6–18 months depending on species, log size, and climate. Once colonized, a single 4-foot shiitake log can produce mushrooms for 4–6 years with proper care. The yield per season is lower than bags on a per-substrate-pound basis, but the labor input drops dramatically once logs are inoculated — you just soak, wait, and harvest. Logs are ideal for homesteaders who want a low-maintenance perennial system and have access to fresh-cut hardwood.
The main limitation of logs is the 1–2 year wait for first production. This also means you cannot adjust anything once the log is inoculated — if you cut your logs at the wrong time (when sap is running hard in spring, bringing competing organisms into the wood), or use wood with too high a moisture content, you wait a year to find out the batch failed. Best practices: cut logs in fall or winter (dormant season), use logs 3–8 inches in diameter (surface area to volume ratio for efficient colonization), and inoculate within 1–4 weeks of cutting before the log dries out excessively or competing fungi establish.
Spawn rate is expressed as a percentage of dry substrate weight. Most species do well at 10–15% spawn rate — this calculator uses 15% as the standard rate for all species except oyster on straw, where 20% is common because straw is a more competitive substrate. Higher spawn rates (20–25%) colonize faster and reduce contamination risk but cost more. Grain spawn (rye, wheat, oat) is the most common form for bags and blocks. Plug spawn is used exclusively for logs. Sawdust spawn can be used for both but is less common for log work. Order spawn from a reputable supplier and use it fresh — stored spawn (even refrigerated) loses viability after a few months and is a common cause of failed grows.
Field capacity is the target hydration level for mushroom substrate — typically 60–65% moisture content by weight. At field capacity, a handful of substrate squeezed as hard as you can should produce just 1–2 drops of water, not a stream. If water pours out freely, the substrate is too wet; mycelium will suffocate and anaerobic bacteria will take over. If no water comes out at all, the substrate is too dry; colonization will be slow and incomplete, and fruiting will be poor. To hit field capacity from dry hardwood sawdust, add roughly 1.6 lbs of water per lb of dry substrate (this calculator shows the exact amount). Different substrate materials have different starting moisture levels, so always go by the squeeze test rather than formula alone.
Mushrooms are the fruiting bodies of mycelium networks. When a colonized block fruits for the first time, the mycelium has had weeks to accumulate energy reserves throughout the entire substrate. The first flush draws on all of those reserves simultaneously, producing the heaviest harvest. After the first flush, the mycelium needs to rebuild its nutrient stores from the remaining substrate before fruiting again. Each successive flush draws from a smaller nutrient pool — the substrate is gradually exhausted — so yields decline with each flush. Typical decline is 30–50% per flush for bags and blocks. Logs decline more slowly because they fruit seasonally and the wood decomposes gradually over years. A common commercial practice is to discard or compost bags after the second flush, since the labor and space cost of maintaining a third and fourth flush often exceeds the value of the additional mushrooms.
Spent mushroom substrate is one of the most underrated garden amendments. After your blocks are done fruiting, the substrate is partially broken down by mycelium into a form that plants can access more readily than raw wood chips or sawdust. Mix spent substrate into compost, use it as a mulch, or incorporate it directly into garden beds at 10–20% by volume. The mycelium in spent substrate also inoculates your soil with beneficial fungi that improve water retention and nutrient cycling. Oyster mushroom SMS is particularly valued because Pleurotus species are also documented lignin degraders that can help break down heavy metals in contaminated soil — they are used in bioremediation research for this property. The only caution: if your substrate had a contamination problem (visible green, black, or pink mold), compost it hot before using it in the garden, or simply bury it deep away from your grow space.
Oyster mushrooms — specifically blue/grey oyster and pink oyster depending on your climate — offer the fastest return. Colonization in 2–3 weeks, first flush 1–2 weeks after that, and oyster mushrooms command $10–18/lb at farmers markets in most regions. The limiting factor is usually shelf life: fresh oyster mushrooms are delicate and last only 5–7 days refrigerated, so you need a local market within 1–2 days of harvest. Lion's mane has similar turnaround times and often commands even higher prices ($15–25/lb) because of its culinary novelty and medicinal reputation, but demand is more variable. Shiitake has a better shelf life (10–14 days fresh, easily dried for longer storage) and steady demand at $8–15/lb, making it a more reliable commercial species if you can accept slower colonization and the cold-shocking process.