Mushroom Yield Estimator
Predict your fresh harvest from a batch — honest low / mid / high range by species and flush count.
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How the formula works
This is the inverse of the biological-efficiency calculator. The BE calc takes a finished grow (harvest → BE %); this one runs the math the other direction (substrate → predicted harvest) before you ever start a batch.
- Predicted fresh yield = dry substrate weight × BE ÷ 100
- Low / mid / high range uses the typical BE band for your chosen species — oysters trend high (100–185%), shiitake lower (75–125%), reishi lowest (50–100%)
- Dry weight estimate ≈ fresh × 0.10. Mushrooms are ~90% water
The flushes don't arrive evenly. The first flush is the largest and yields decline from there:
- 1 flush total: 100%
- 2 flushes: ~62% / 38%
- 3 flushes: ~50% / 32% / 18%
- 4 flushes: ~45% / 28% / 17% / 10%
Worked example
Target: 1 kg (1000 g) of dry CVG substrate, growing oysters, planning for 2 flushes.
- Oyster BE band: low 100%, mid 145%, high 185%
- Total fresh range: 1000 g – 1850 g (mid 1450 g)
- Estimated dry weight (mid): 1450 g × 0.10 ≈ 145 g
- Flush 1 (~62% of mid): ~899 g
- Flush 2 (~38% of mid): ~551 g
That's a single 6-quart monotub's worth of substrate. If your actual harvest comes in at 800 g, you landed in the “below average” band; 1.6 kg and you're in “exceptional” territory. Run the BE calc on the finished grow to see exactly where you fell.
When to use this calculator
Why a range, not a single number:mushroom yield is wildly variable. Two growers with the same substrate, same species, and identical-looking conditions can land 30–50% apart. Strain genetics, humidity stability, fresh air exchange, light, water content of the substrate, casing technique, harvest timing — all of it stacks. Anyone promising you a single “X grams from Y substrate” figure is selling you a fantasy. The honest answer is a band, and the band is what we show.
The flush decline curve:the first flush is always the biggest, often half or more of total yield. Each subsequent flush is smaller as the substrate runs out of nutrients. Past the third flush you're usually getting diminishing returns — the substrate is spent and the contamination risk climbs the longer it sits in the fruiting chamber. Most home growers plan for 2–3 flushes per batch.
How to use this for batch sizing:work backwards from your goal. Want roughly 1 kg of fresh oysters? At an oyster mid of 145%, that's about 700 g of dry substrate (1 kg ÷ 1.45). Want 500 g of fresh shiitake? Shiitake mids around 100%, so plan on roughly 500 g of dry substrate — and pad it because shiitake variance is wide.
This is a planning tool, not a guarantee.Pair it with the BE calculator after the grow finishes: did you hit the predicted range? If not, the BE calc tells you which band you actually landed in, which feeds back into next batch's plan. That feedback loop — plan, grow, measure, adjust — is how you tighten your numbers over time.
Frequently asked questions
Why is the predicted range so wide?
Because mushroom yield genuinely is that variable. Strain, hydration, FAE, humidity, casing depth, harvest timing, and substrate freshness all move the needle. A tight 10% range would be dishonest — even experienced growers see 30–50% variation between otherwise-identical batches. The wide band is the truth, not a hedge.
How many flushes should I plan for?
Most home growers plan for 2–3 flushes per batch. The first flush is the largest (roughly half of total yield), the second is smaller, and the third is usually a token harvest. After three flushes the substrate is spent and contamination risk rises sharply — most experienced growers cut their losses and start a fresh batch rather than chasing a fourth flush.
Can I trust this for commercial planning?
Use it as a starting point, not a contract. Commercial planning needs your own historical batch data — your specific strain, your specific environment, your specific technique. Run a few batches, log every harvest into First Flush, and your actual BE numbers will be more accurate than any species-average band. This calculator is the right tool for hobby planning and for sanity-checking your first few commercial batches against typical bands.
What's a 'good' yield for my species?
For oysters: 100% BE is solid, 150% is great, 185%+ is exceptional. For shiitake: 75% is solid, 100% is the sweet spot, 125%+ is exceptional. For lion's mane: 90% solid, 115% great, 140%+ exceptional. Reishi runs lower across the board (50–100% is the full range). See the species database for typical BE bands for every species we track.
Related resources
- Biological efficiency calculator — After harvest, calculate your actual BE and see which band you landed in.
- CVG substrate calculator — Mix the right amount of bulk substrate for the batch size you're planning.
- Spawn-to-bulk calculator — Match grain spawn weight to your bulk substrate.
- Species database — Typical BE bands and growing parameters per species.
Want to log every batch and let First Flush do this math automatically? Create a free account or see what comes with First Flush Pro.