Mushroom PF Tek Calculator

PF Tek (Perlite & Flour Technique, originally devised by Robert "Psylocybe Fanaticus" McPherson) is the most beginner-friendly substrate preparation method in amateur mycology. It uses a simple, two-ingredient substrate — Brown Rice Flour (BRF) and coarse Vermiculite — combined with water and sterilised inside mason jars.

The method gained legendary status in cultivation communities because it requires minimal equipment, produces reliable colonisation, and allows cultivators to observe mycelium growth through clear glass jars. Each inoculated jar becomes an independent "cake" that fruits on its own once colonised — making it an ideal entry point for anyone new to mushroom cultivation.

This calculator takes the guesswork out of preparation. Instead of estimating by eye or doing manual arithmetic for large batches, simply enter your jar count, size, and preferred ratio, then get exact measurements instantly — helping you minimise waste, prevent contamination from overly wet or dry substrate, and replicate successful batches every single time.

The calculator works in three sequential stages:

1. Volume calculation: It first determines the usable substrate volume per jar by multiplying jar capacity (ml) by your chosen fill percentage. This ensures adequate headspace for gas exchange during colonisation.
2. Ratio partitioning: The total substrate volume per jar is divided among BRF, Vermiculite, and Water according to your selected or custom ratio. Each ingredient's share is calculated as a proportion of the total ratio sum.
3. Batch scaling: Per-jar values are multiplied by your jar count to produce total batch quantities. Results are then converted into your preferred measurement unit — millilitres, tablespoons, cups, or grams.

The dry vermiculite casing layer (if enabled) adds an extra unmixed layer of dry vermiculite on top of the substrate inside each jar before pressure cooking or steam sterilisation. This layer acts as a physical barrier, absorbing surface moisture and blocking airborne contaminants from reaching the colonising mycelium during and after inoculation.

The core mathematics behind every calculation this tool performs:

Unit conversions used: 1 tbsp = 15 ml | 1 US cup = 240 ml | 1 ml BRF ≈ 0.53 g | 1 ml Vermiculite ≈ 0.12 g | 1 ml Water = 1 g

• Eliminates guesswork: Eyeballing ingredients introduces inconsistency across jars, leading to uneven colonisation speeds or failed cakes. Precise measurement removes this variable entirely.
• Contamination control: Substrate that is too wet creates a microenvironment that favours bacterial and mould growth over mycelium. This tool helps you stay within the safe moisture window for each ratio.
• Batch consistency: When jars are prepared identically, you can accurately attribute successes or failures to a single variable — making iterative improvement scientific rather than anecdotal.
• Time & material efficiency: Scaling up from 5 to 50 jars is instant. No spreadsheets, no pencil arithmetic, no wasted substrate from over-preparation.
• Beginner confidence: New cultivators can follow the calculator's output as a step-by-step recipe, removing the anxiety of "did I get the ratio right?" that often accompanies first attempts.
• Printable reference: Use the Print button to create a physical or PDF checklist you can keep at your workstation during preparation — keeping your phone or screen out of the sterile workspace.