Calculators
Four bits of arithmetic that come up in every grow. All of it runs in your browser — nothing is sent anywhere.
Spawn rate
Higher spawn rates colonise faster and resist contamination better, because your mycelium reaches the whole substrate before anything else can establish. 1:2 is fast and expensive; 1:4 is the usual compromise.
3.3 lb
of grain spawn needed
Substrate hydration
Field capacity is the target: a firm squeeze yields a few drops, not a stream. Most bulk substrates want roughly 60–65% moisture by total weight, which is more water than dry material.
7.5 lb
of water to add
Master's Mix
Equal parts hardwood fuel pellets and soy hull pellets by dry weight, hydrated to about 60%. The standard high-performance substrate for wood-loving species — and nutritious enough that it must be sterilised, never pasteurised.
6.0 lb
hardwood pellets
6.0 lb
soy hull pellets
18.0 lb
water
Biological efficiency
Fresh mushroom yield as a percentage of dry substrate weight. 100% means a pound of mushrooms from a pound of dry substrate. It is the only number that lets you compare a straw grow with a sawdust grow honestly.
80%
biological efficiency
Every figure here is a starting point, not a promise. Strain, supplementation and how well your chamber actually holds conditions move all of them.