Climate & Humidity Calculator
See the temperature, humidity, fresh air and CO₂ each mushroom wants at every phase — colonization, pinning and fruiting — pulled from the cultivation database.
Then enter what your own grow space reads, and the calculator works out the vapour pressure deficit, dew point and absolute humidity of your air, tells you whether you're on target, and names what to change. VPD and dew point are the professional metrics most hobby calculators skip — they're what separates consistent flushes from aborted pins.
Where you are
Pick a species and phase for the target, then enter what your grow space actually reads.
VPD (vapour pressure deficit) is how strongly the air pulls moisture from your mushrooms — fruiting wants it low. Dew point warns when surfaces get wet enough for bacterial blotch. Targets are literature-range: reconfirm for your strain.
How to use it
- Pick your species. Its temperature and humidity targets load from the database.
- Pick the phase. Colonization, pinning or fruiting — each wants different temperature, humidity and airflow.
- Enter your readings. Type the temperature and humidity your hygrometer actually shows.
- Read the verdict. VPD, dew point and absolute humidity, an on-target or adjust call, and concrete fixes — raise humidity by X, drop temperature by Y, add fresh air.
Questions
What is VPD for mushrooms?
Vapour pressure deficit — how strongly the air pulls moisture out of your mushrooms. Fruiting mushrooms want it low; too high and pins dry out and abort before they mature.
What humidity do mushrooms need to fruit?
Most gourmet species fruit at 85–95% relative humidity, with the exact target depending on species and phase. Pinning often wants the high end of that.
Why does my grow get condensation?
When the air sits near its dew point, moisture condenses on cool surfaces — a route in for bacterial blotch. Gentle airflow keeps surfaces dry.
What is fresh-air exchange (FAE)?
Swapping stale, CO₂-rich air for fresh air. Mushrooms breathe out CO₂; too little FAE gives long stems and small caps, too much dries them out.