Vermiculite/Perlite Add-in Calculator Guide
Use this vermiculite and perlite add-in calculator to find how much aeration amendment to blend into potting soil. Enter total mix volume in liters or quarts and desired add-in percentage to improve drainage and root oxygen.
How to use the vermiculite/perlite calculator
Enter total soil or potting mix volume in liters or quarts. Set desired vermiculite or perlite percentage (typically 10–30% for containers).
The result is add-in volume in the same unit — choose vermiculite for moisture retention or perlite for maximum drainage.
Add-in volume formula
Add-in volume = Total mix volume × (Percentage ÷ 100). The percentage is of final blended volume, not just the base soil component.
- Add-in = total volume × (pct / 100)
- Perlite: best drainage and aeration; floats when overwatered
- Vermiculite: holds moisture and nutrients; compacts over time
- Common range: 15–25% for general containers
Worked example
Improving 10 liters of store-bought potting mix with 20% perlite: Add-in = 10 × 0.20 = 2 liters of perlite.
Blend evenly before filling containers — final mix volume is approximately 10 liters of amended media.
Perlite vs vermiculite
Perlite is expanded volcanic glass — lightweight, excellent aeration, ideal for succulents, seed starting, and heavy-feeding vegetables. Vermiculite is layered silicate that holds more water — better for germination and moisture-loving plants.
Do not use both at full rate simultaneously unless following a tested recipe.
Mixing tips
Wear a dust mask when handling dry perlite or vermiculite. Pre-moisten mix after blending. See potting mix recipe calculator for full multi-component blends from scratch.
- 20% perlite is a common upgrade for bagged potting soil.
- Seed mixes often use 30–50% perlite or vermiculite.
- Avoid inhaling fine dust — wet ingredients when possible.
- Pair with bottom watering estimator for container irrigation timing.