Monthly Castings
8.4 lbs/month
Capacity
3.5 lbs/wk
Annual
101 lbs
Savings
$76
Indoor bins are unaffected by seasonal changes
CAN HANDLE
Surplus: 0.5 lbs/week
3.5 lbs/wk capacity vs 3 lbs/wk waste
Monthly Output
8.4 lbs
Annual Output
101 lbs
Annual Savings
$76
Temp Factor
100%
Nitrogen (N)
1.5 lbs
Phosphorus (P)
1 lbs
Potassium (K)
1 lbs
Store castings avg $0.75/lb • Chemical fertilizer avg $0.15/lb equivalent
Inputs
Result
1 lb of red wigglers at 70°F (1.0 temp factor, 1.0 indoor) processes 0.5 lbs/day = 3.5 lbs/week. Surplus of 0.5 lbs/week. Monthly castings: 3.5 × 0.6 × 4 = 8.4 lbs. Annual output: 100.8 lbs, saving ~$76 vs store castings.
Inputs
Result
3 lbs at 75°F (1.0 factor) in summer (1.0 outdoor) processes 1.5 lbs/day = 10.5 lbs/week. Surplus of 3.5 lbs/week. Monthly castings: 10.5 × 0.6 × 4 = 25.2 lbs. Annual: 302 lbs at ~$227 value.
Inputs
Result
2 lbs of nightcrawlers at 45°F (0.25 factor) in winter (0.3 outdoor) processes 0.053 lbs/day = 0.37 lbs/week. Overloaded by 4.63 lbs/week. Monthly output: only 0.37 × 0.55 × 4 = 0.8 lbs. Move bin indoors or reduce feeding drastically.
Red wigglers eat about half their body weight per day under optimal conditions (60-80°F). For 3 lbs of weekly food waste, you need about 1 lb of worms (3 lbs / 7 days / 0.5 rate = 0.86 lbs). Start with 1 lb and let the population grow to match your waste output.
| Weekly Waste | Red Wigglers Needed | European Nightcrawlers | Bin Size |
|---|---|---|---|
| 2 lbs/week | 0.6 lbs | 0.8 lbs | Small (10 gal) |
| 3 lbs/week | 1 lb | 1.2 lbs | Medium (20 gal) |
| 5 lbs/week | 1.5 lbs | 2 lbs | Large (30 gal) |
| 7 lbs/week | 2 lbs | 2.9 lbs | XL (40 gal) |
Red wigglers convert about 60% of their food intake into castings. With 1 lb of worms processing 3.5 lbs per week, you get about 2.1 lbs of castings weekly, or 8.4 lbs monthly. Over a year at optimal conditions, that is roughly 100 lbs of finished vermicompost.
Vermicompost typically has NPK values of 1-2% nitrogen, 1% phosphorus, and 1% potassium. While lower in concentration than chemical fertilizers, castings provide slow-release nutrients, beneficial microorganisms, and improved soil structure that synthetic products cannot match.
| Nutrient | Vermicompost | Hot Compost | 10-10-10 Fertilizer |
|---|---|---|---|
| Nitrogen (N) | 1–2% | 0.5–1% | 10% |
| Phosphorus (P) | 1% | 0.5% | 10% |
| Potassium (K) | 1% | 0.5–1% | 10% |
| Microbes | Very High | Moderate | None |
The optimal range for red wigglers is 60-80°F, where they process food at full capacity. Below 50°F, worms become nearly dormant (25% activity). Above 90°F is dangerous and can kill the colony. European nightcrawlers prefer slightly cooler temps at 55-75°F.
Commercial worm castings cost $0.50-$1.00 per pound, while chemical fertilizer equivalents run about $0.15 per pound. A 1 lb worm bin producing 100 lbs of castings annually saves $50-$100 versus buying castings, plus you divert 180+ lbs of food waste from the landfill each year.
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Last Updated: Mar 9, 2026
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