Potting Mix Worksheet
A part is any container, used the same way every time. Buy in DRY quarts - they are 16% bigger than liquid ones.
BFCBrilliance · bfcbrilliance.com/tools/potting-mix-ratio-calculator
The arithmetic and the units
- Cylinder volume
- 3.14159 x radius² x depth
- Real pot volume
- less than that — pots taper
- 1 US DRY quart
- 67.2006 cubic inches
- 1 US LIQUID quart
- 57.75 cubic inches
- ⚠ Dry is bigger by
- about 16.4% — mix is sold DRY
- 1 cubic foot
- 1728 cu in = 25.71 dry quarts
- 1 dry quart
- about 1.101 litres
- An ingredient's share
- its parts ÷ total parts
Your batch
- Date
- Plant or purpose
- Pot diameter
- Pot depth
- Taper allowance
- Number of pots
- MIX PER POT
- TOTAL MIX
- Base parts
- Aeration parts
- Compost parts
- Amendment parts
- TOTAL PARTS
Recipes that worked - keep the ones you like
| Plant or purpose | Base | Aeration | Compost | Amendment | How it did |
|---|---|---|---|---|---|
Mixing day
- Coir bricks soaked and broken up BEFORE measuring parts
- Peat and coir dampened - dry, they repel water
- One container used as the part, levelled the same way each time
- Buying in DRY quarts or cubic feet, not liquid quarts
- A little extra made - mix compresses and settles
- Pots filled without ramming
- Watered in, then topped up a week later
- Recipe written down with the plant it was for
A dry quart is not a liquid quart
67.2006 cubic inches against 57.75 - the dry quart is about 16.4% larger, and it is the one bagged mix is sold in. Convert a batch sized in liquid quarts and you over-buy by a sixth. Do it the other way round and you are short on the last pot, which is when you find out.
Measure parts the same way every time
A part is any container you like, but it has to be the same one, filled the same way. A heaped scoop of perlite against a struck scoop of compost is a different recipe from the one you wrote down - and it is the most common reason a mix that worked last year does not this year.