Calculating typical soil requirements for your grow


Indoors we recommend 8L to 10L of Soil for every 100w of light - Per plant for water only runs.


A simple formula to calculate soil use is:

Light Wattage / Plant Number / 100w X 8L to 10L


For example a 1 plant system: 

600w / 1plant = 600w / 100w X 10L = 60L


Another example using smaller plants indoors under one light:

1000w / 4plants = 250w / 100w X 8L = 20L Per Plant.

Outdoors or in Greenhouse use we recommend 8L to 10L Per Plant - Per week of growth. 


A simple formula to calculate outdoor and greenhouse use is:

Weeks of growth X 8L to 10L X Plant number



16 weeks X 8L X 1plant = 128L

We recommend using this much soil to ensure adequate root space and nutrition for the entire length of the crop.


This calculation is based on a well lit garden with good air flow and space for plants.


Smaller grows with less light or cramped conditions can get away with less soil. 


Because the soil contains all the required fertilizer for the grow it is important to ensure enough soil capacity for the length of the cycle. Plants also grow better, more compact and healthier when their roots have room to move freely.


A larger bio-mass means more bacterial and fungal life and a more active soil-food-web.

If you are using less soil, or one of our Basic blends it is advisable to apply some top dressings and liquid boosters or compost tea at regular points throughout the grow to keep everything humming.


For example the optimal amount of soil for a 10 week grow (2 Weeks Grow / 8 Weeks Flower)  is between 80L and 100L. A 24Gal Grow Pot is perfect.