Mushroom Cultivation
PF Tek Substrate Calculator
Work out exactly how much vermiculite, brown rice flour and water to prepare for any number of PF Tek jars — scaled to your jar size, with metric weights and a dry-vermiculite top layer included.
Enter a whole number between 1 and 500.
Enter a whole number between 50 and 2000 mL.
Your substrate shopping list
| Ingredient | Volume (cups) | Volume (mL) | Approx. weight |
|---|
Overview
PF Tek (the Psilocybe Fanaticus Technique) is the classic beginner method for growing gourmet and research mushrooms on brown rice flour cakes in glass jars. It is popular precisely because it needs no expensive equipment — just jars, vermiculite, brown rice flour and water.
The hard part for most first-time growers is scaling the recipe. A single jar recipe is easy to remember, but the moment you prepare a batch of 6, 12 or 24 jars — or switch from half-pints to pints — the mental arithmetic gets error-prone, and getting the water ratio wrong is a leading cause of failed or contaminated cakes. This calculator does that scaling for you, in both cups and metric units, so every jar in the batch is mixed to the same reliable field-capacity moisture level.
How It Works
- Enter the number of jars you plan to fill.
- Pick your jar size — half-pint or pint — or choose Custom and type the jar's volume in millilitres.
- Press Calculate. You'll get the total vermiculite, brown rice flour and water for the whole batch, plus a per-jar reminder and the dry vermiculite you need for the top contamination layer.
- Mix the vermiculite and water first until evenly damp, then fold in the brown rice flour, fill jars to about ½ inch from the top, and finish with the dry vermiculite cap.
- Press Reset to clear everything and plan a different batch.
Formula Explanation
Every calculation scales from the standard PF Tek ratio for one half-pint (237 mL) jar:
The tool first works out a scale factor from your jar size, then multiplies each ingredient by the number of jars:
- Scale factor = your jar volume ÷ 237 mL (so a pint = 2.0, a 300 mL jar ≈ 1.27)
- Ingredient total = base amount × scale factor × number of jars
- Dry vermiculite top layer = ⅛ cup per half-pint, scaled the same way
Metric weights use practical bulk densities — roughly 0.10 g/mL for loose vermiculite, 0.55 g/mL for brown rice flour and 1.00 g/mL for water — so the gram figures reflect real kitchen scales rather than idealised values.
Practical Benefits
- Consistent moisture across the batch. Every jar gets the same water ratio, which is the single biggest factor in avoiding wet, contamination-prone cakes.
- Shop with confidence. Know how much vermiculite and brown rice flour to buy before you start, in both cups and grams.
- Scale without mistakes. Jump from 3 jars to 30, or from half-pints to pints, without redoing the maths by hand.
- Fewer wasted materials. Mix the right amount instead of guessing and throwing out leftover substrate.
Frequently Asked Questions
Disclaimer
This calculator is provided for general educational and informational purposes only. Ingredient quantities are estimates based on the standard PF Tek ratio and typical material densities; actual results vary with materials, technique and local conditions. Always follow the laws and regulations in your jurisdiction regarding mushroom cultivation.
