Calculator Form
Use the responsive calculator grid below. Large screens show three columns, smaller screens show two, and mobile shows one.
Plotly Graph
The chart compares total media, vermiculite share, non-vermiculite share, and buy volume. Calculate first to update the graph with your values.
Example Data Table
| Example | Project details | Total media | Vermiculite % | Required vermiculite | Suggested purchase |
|---|---|---|---|---|---|
| Raised bed mix | 240 cm × 120 cm × 20 cm bed | 576.00 L | 20% | 126.72 L | 2 bags of 100 L |
| Round pot blend | 40 cm diameter × 35 cm height | 43.98 L | 25% | 12.09 L | 1 bag of 20 L |
| Seed tray start mix | 72 cells × 45 ml each | 3.24 L | 35% | 1.25 L | 1 small bag |
Formula Used
Volume formulas
Rectangular bed: Volume = Length × Width × Depth
Round pot: Volume = π × Radius² × Height
Seed tray: Volume = Cell Count × Volume per Cell
Custom volume: Use the total medium volume directly.
Vermiculite formulas
Effective media volume: Base Volume × Fill % × Compaction Factor
Base vermiculite: Effective Media Volume × Vermiculite %
Final vermiculite: Base Vermiculite × (1 + Wastage %)
Bag count: Ceiling(Final Vermiculite ÷ Bag Size)
All internal calculations are normalized to liters for consistent conversions, bag counts, and cost estimates.
How to Use This Calculator
- Select the project type that matches your gardening task.
- Enter the bed, pot, tray, or direct media volume values.
- Choose the percentage of vermiculite you want in the mix.
- Set fill percentage, wastage allowance, and compaction factor if needed.
- Enter bag size and bag price for purchase planning.
- Press Calculate Vermiculite to see the result above the form.
- Review the chart, conversions, and purchase estimate.
- Use the CSV or PDF buttons to save the result.
Frequently Asked Questions
1. Why would I add vermiculite to a garden mix?
Vermiculite improves water retention, air space, and nutrient holding capacity. It is especially useful in seed starting blends, potting media, and light raised-bed mixes that need better moisture management.
2. What vermiculite percentage works well for seed starting?
Many seed-starting mixes use about 20% to 40% vermiculite by volume. The right amount depends on watering habits, drainage needs, and how much compost, peat, or coco coir is included.
3. Is more vermiculite always better?
No. Too much vermiculite can hold excess moisture and reduce structural balance in the mix. A moderate ratio usually gives better performance for roots, especially when combined with compost and aeration materials.
4. Why does the calculator include a wastage allowance?
Wastage allowance helps cover spillage, measuring losses, settling, and slight overfilling. It makes your purchase estimate more practical, especially when you buy packaged bags instead of bulk material.
5. What does the compaction factor change?
Compaction factor adjusts for settling after mixing or watering. A value above 1.00 increases the effective medium estimate, while values near 1.00 suit loose, freshly blended growing media.
6. Can I use this for raised beds and containers?
Yes. The calculator supports rectangular beds, round pots, seed trays, and direct custom volume entries. That makes it useful for container gardeners, propagation work, and raised-bed planning.
7. Why does bag count round up?
Bags are whole purchase units. If the calculation needs 121 liters and each bag holds 100 liters, you still need two bags. Rounding up avoids underbuying and project delays.
8. What bulk density should I enter?
Use the product label when available. If you do not have one, enter your best estimate. Density mainly affects weight output, not the core volume calculation for vermiculite requirements.