Pot & Potting Mix Calculator
Calculate the growing medium for one pot or a whole planting session. Deduct an existing root ball, divide your own blend into ingredients, and turn the result into a practical shopping list.
Measure inside the container at your planned soil level. Choose the shape, enter the dimensions, and calculate your plan.
Growing medium to prepare
19.44litres
17.65 US dry qt · 0.686 ft³
1 round pot · 30 cm diameter · 25 cm fill depth · 10% extra
- Fill volume per pot
- 17.67 L
- Root ball per pot
- 0 L
- New medium before extra
- 17.67 L
Prepare your materials
| Material | Recipe | Prepare |
|---|---|---|
| Selected base medium | 100% | 19.44 L |
Enter the actual bag size to calculate how many bags of base medium to prepare.
How this plan is calculated
Round-pot volume = π × radius² × fill depth. Deduct the root-ball volume, multiply by the number of containers, then add your chosen extra percentage.
Gather Your Potting Supplies
Bring the growing medium, containers and handling tools together for your next planting session.
All-purpose potting mix
Prepare the base medium for a suitable container-growing project.
View on Amazon →Indoor repotting mat
Keep loose medium together while filling and changing pots.
View on Amazon →Clear nursery pots
Prepare draining containers with visible growing medium.
View on Amazon →Long-spout watering can
Direct water towards the growing medium with a controlled spout.
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Practical Digital Guides
Build on your potting plan with practical growing methods, plant-care routines and your next container project.
Browse digital guides →Potting Mix Calculator FAQ
Which measurements should I enter?
Measure the inside of the container. Fill depth runs from the inside base to the soil line you plan to use. For tapered pots, enter the diameter at that soil line and the inside bottom diameter.
How does the root-ball deduction work?
The calculator subtracts the root ball and the medium you will keep around it from each pot's fill volume. Use the same estimated root-ball volume for each container in the batch, or calculate different containers separately.
Does this tool choose an ingredient recipe?
You choose the base medium and ingredient percentages. The calculator converts that recipe into preparation volumes. Leave custom blending off to calculate a single ready-made medium.
How are bag quantities calculated?
Enter the actual bag size and its labelled volume unit. The calculator divides the required base-medium volume by that bag size and rounds up to a whole bag. Other ingredients keep their own volume totals.
Why are dry and liquid quarts listed separately?
A US dry quart is about 1.101 litres; a US liquid quart is about 0.946 litres. Select the unit used on the package so the bag calculation uses the correct conversion.
Can I keep my plan for another session?
Use Save on this device to keep the inputs in this browser, then Restore saved plan when you return. Copy plan and Print create a portable record of the calculated quantities.
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