Garden Soil Calculator
🌱 How to Calculate Garden Soil – Complete Guide
A soil calculator for raised garden beds eliminates guesswork and saves 40-50% on costs. Whether you’re using a potting soil calculator or calculating for vegetable gardens, accurate measurements are essential.
- 12-24 inches is ideal depth for most vegetables
- Soil settling reduces volume by 10-15% over 60 days
- Homemade mixes cost 40-48% less than store-bought
- Perfect soil mix = 40% topsoil, 30% compost, 20% cocopeat, 5% perlite, 5% vermiculite
📐 Basic Calculation Formula
Example: For a 4×8 ft bed at 12 inches deep:
- 4 ft × 8 ft × 1 ft = 32 cubic feet
- = 0.59 cubic yards
- = 905 liters
- = approximately 16-22 bags (40L bags)
| Garden Shape | Formula | Example |
|---|---|---|
| Rectangle | L × W × D | 4×4×1 ft = 16 cu ft |
| Circle | π × (D÷2)² × Depth | 4 ft diameter = 12.6 cu ft |
| Odd Shapes | Divide into rectangles | L-shaped = 2 rectangles |
🛍️ How Many Bags Do You Need?
| Bed Size | Depth | Volume | Bags (40L) |
|---|---|---|---|
| 2×4 ft | 12 in | 8 cu ft (226L) | 6 bags |
| 4×4 ft | 12 in | 16 cu ft (453L) | 12 bags |
| 4×8 ft | 12 in | 32 cu ft (905L) | 23 bags |
| 4×10 ft | 12 in | 40 cu ft (1,132L) | 28 bags |
💡 Pro Tip: Add 10-15% extra soil for settling, compaction, and future top-dressing.
🌍 Soil Mix Ratio Customizer
The Ultimate Mix (works for 90% of plants):
| Component | Percentage | Purpose | Per 100L |
|---|---|---|---|
| Topsoil | 40% | Structure & nutrients | 40L |
| Compost | 30% | Organic matter | 30L |
| Cocopeat | 20% | Water retention | 20L |
| Perlite | 5% | Drainage | 5L |
| Vermiculite | 5% | Moisture & roots | 5L |
Alternative Mixes
- High Drainage: 40% topsoil, 35% sand, 25% compost (for clay areas)
- Water Retention: 35% topsoil, 35% compost, 20% cocopeat, 10% vermiculite (dry climates)
- Budget Mix: 50% topsoil, 50% homemade compost (cost-effective)
🌱 Plant-Specific Soil Needs
| Plant | Depth | Best Mix Ratio | pH Goal | Volume/Plant |
|---|---|---|---|---|
| Tomatoes | 24 in | 40-30-25-5 | 6.2-6.8 | 18-20L |
| Garlic | 8 in | 50-25-15-10 | 6.0-7.0 | 10-12L |
| Herbs | 6 in | 30-35-25-10 | 6.5-7.0 | 8-10L |
| Root Vegetables | 12 in | 40-20-20-20 | 6.0-6.8 | 15-18L |
| Balcony Plants | 5-8 in | 30-25-30-15 | 6.5 | 5-10L |
💰 Cost Comparison – India vs USA
| Bag Size | India (₹) | USA ($) |
|---|---|---|
| 40L Soil | ₹180-220 | – |
| 50L Soil | ₹240-300 | – |
| 2 cu ft Soil | – | $3-5 |
| Bulk Soil/yard | ₹2,000-3,000 | $25-45 |
💡 Savings Hack: Buy bulk soil + make compost = 48% cheaper than bagged mixes.
🌍 Soil pH Calculator
Correct pH determines nutrient availability. Here’s what each crop needs:
| Plant | Optimal pH | Problem if Wrong |
|---|---|---|
| Tomatoes | 6.2-6.8 | Below 6.0 = Calcium deficiency (blossom end rot) |
| Garlic | 6.0-7.0 | Above 7.5 = Poor bulb development |
| Herbs | 6.5-7.0 | Below 6.0 = Nutrient lock, yellowing |
| Peppers | 6.0-6.8 | Above 7.0 = Aluminum toxicity |
How to Adjust pH
- To RAISE pH: Add dolomitic lime (1-1.5 lbs per 100 sq ft)
- To LOWER pH: Add elemental sulfur (0.5-1 lb per 100 sq ft)
- DIY Test: Mix soil with white vinegar. If it fizzes, pH is high.
📊 Water Retention Score
Formula: Base (6) + (Cocopeat % × 0.18) + (Vermiculite % × 0.07) − (Perlite % × 0.08)
| Score | Rating | What to Do |
|---|---|---|
| 1-3 | Very Poor | Add compost or cocopeat |
| 4-6 | Below Average | Reduce perlite, add organic matter |
| 7-8 | Good | Perfect for most vegetables |
| 9-10 | Excellent | Ideal for herbs & balcony plants |
🌍 Carbon Footprint – Eco-Friendly Gardening
| Method | CO₂ per 100L | Savings |
|---|---|---|
| Store-bought soil | 45 kg CO₂ | – |
| Homemade mix | 20 kg CO₂ | 25 kg (56% less) |
For a 500L garden: Homemade mix saves 125 kg CO₂ = planting 20 trees annually!
📉 Soil Settling Predictor
| Time Period | Settlement % | Action |
|---|---|---|
| Day 1-7 | 3-5% | Water thoroughly |
| Week 2-4 | 5-8% | Check depth |
| Month 2 | 10-12% | Begin top-dressing |
| Month 3 | 12-15% | Add 1-2 inches |
Formula: Settling % = 12 − (Cocopeat % ÷ 230)
❓ Quick FAQ
Q: How much soil for a 4×8 bed?
A: 32 cubic feet (905L) = 16-22 bags (40L) = ₹2,880-4,800 (India) or $35-70 (USA)
Q: Can I use potting soil in raised beds?
A: Not ideal. It’s too expensive and moisture-retentive. Use custom 40-30-20-5-5 mix instead.
Q: How often replace soil?
A: Every 3-5 years, OR maintain by adding 1-2 inches compost yearly + crop rotation + soil testing.
Q: Cocopeat vs Peat Moss?
A: Choose cocopeat: renewable, eco-friendly, lower cost, better for sustainability.
Q: Should I add extra soil for settling?
A: YES. Order 10-15% extra. Soil settles 10-15% over 60 days.
🚀 Start Calculating Now!
Use the Garden Soil Calculator above to:
- ✅ Calculate exact soil volume needed
- ✅ Get plant-specific mix recommendations
- ✅ Estimate total cost (India & USA pricing)
- ✅ Check water retention scores
- ✅ See carbon footprint savings
- ✅ Predict soil settling
- ✅ Export PDF report
- ✅ Print shopping list
Perfect calculations = Healthier plants + 40-50% cost savings + Zero waste