🪨 Soil Mix Ratio Calculator
Scale any potting soil recipe (like '3 parts soil : 2 parts perlite : 1 part bark') to whatever total batch size you need.
Parts to actual quantities
Every ingredient takes its share of the batch in proportion to its parts:
ingredient volume = (its parts ÷ total parts) × batch sizeThe default 3 : 2 : 1 recipe is six parts in all, so a 12 quart batch works out as 6 quarts of potting soil, 4 of perlite and 2 of orchid bark. Parts accept halves, so 2.5 parts perlite is fine. The unit you pick is only a label — the batch and every result carry it, and no conversion between quarts, litres, gallons and cups happens.
Building the recipe
| Plant type | Common blend | Why |
|---|---|---|
| Aroids (monstera, philodendron) | 1 soil : 1 perlite : 1 bark | Chunky, drains fast, roots get air |
| General foliage | 3 soil : 2 perlite : 1 bark | Holds moisture without staying sodden |
| Cacti and succulents | 1 soil : 2 coarse sand or pumice | Mostly mineral, dries within days |
Add rows for coco coir, worm castings, charcoal or whatever else the recipe calls for. Setting an ingredient to 0 parts leaves it in the list but gives it none of the batch.
Frequently asked questions
What does “3 parts soil to 1 part perlite” mean?
A ratio, not a fixed amount. Four parts in total means the soil is three quarters of the batch and the perlite one quarter, whether you are mixing a cup or a wheelbarrow.
How much perlite should I add to potting soil?
Between a quarter and a half by volume for most houseplants, and more for aroids that want air around their roots. Ordinary bagged potting soil on its own compacts and holds water longer than many indoor plants tolerate.
How much mix do I need for a 6 inch pot?
Around 3 quarts, less the space the root ball takes up. A 6 in wide, 6 in deep pot is about 170 cubic inches and a quart is 57.75, so a 12 quart batch fills roughly four of them.