Potting Mix Recipe Calculator Guide
Use this potting mix recipe calculator to blend peat or coco coir, perlite, and compost at custom percentages. Enter total volume in liters or quarts and adjust component sliders (must sum to 100%) to get exact volumes for each ingredient.
How to use the potting mix recipe calculator
Enter total mix volume in liters or quarts. Adjust peat/coco, perlite, and compost percentages on the sliders — all three must sum to exactly 100%.
Results show volume of each component to measure and blend.
Potting mix blend formula
Component volume = Total volume × (Component % ÷ 100). Apply separately for peat/coco, perlite, and compost. Percentages must sum to 100% before calculating.
- Peat/coco vol = total × (peat% / 100)
- Perlite vol = total × (perlite% / 100)
- Compost vol = total × (compost% / 100)
- Default 50/25/25 is a balanced starting recipe
Worked example
Mixing 20 liters at 50% peat/coco, 25% perlite, 25% compost: Peat/coco = 20 × 0.50 = 10 liters.
Perlite = 20 × 0.25 = 5 liters. Compost = 5 liters. Blend thoroughly before filling containers.
Choosing a potting mix ratio
Peat or coco coir retains moisture. Perlite improves drainage and aeration. Compost adds nutrients and biology. Seed-starting mixes often use higher perlite (40–50%); mature containers tolerate more compost.
Coco coir is a peat-free alternative with similar water-holding capacity — pre-hydrate compressed bricks before measuring.
Mixing and storage tips
Moisten mix before seeding — it should hold together when squeezed without dripping. Store unused dry components sealed; prepared mix is best used within a few weeks unless pasteurized.
- Add slow-release fertilizer per label for long-season containers.
- Sterilize reused mix or replace for disease-sensitive seedlings.
- See raised bed soil compost ratio for in-ground blends.
- 1 US quart ≈ 0.946 liters for cross-unit planning.