Worm Bin Calculator
Worm pounds and bin size from weekly food scraps.
What it does
Worm bins scale from the scrap bucket, not the bin catalog. One pound of red wigglers handles about half a pound of scraps a day in one square foot of shallow bin. A household scrapping 3.5 lb a week needs exactly that starter pound with a 1 square foot home.
The tool above runs Nebraska stocking math. Enter weekly scrap pounds and it prints worm pounds with headcount, bin surface, and the daily feed cap. Two outputs move together: double the scraps and both worms and area double.
University and federal sources agree. Nebraska Extension sets 1 lb per half-pound daily with a square foot per pound in 8 to 12 inch bins, Cornell describes shallow newspaper-bedded worm bins, and EPA counts a starter pound near 1,000 worms with moist-sponge bedding and 3 to 6 month harvests.
Bedding and temperature decide success after sizing. Fluffed shredded paper filled two-thirds, food buried under 2 inches, and 59 to 77 F keep the bin odorless. Start feeding slow; only add more after prior food disappears.
How to use
- Weigh a week of kitchen scraps.
- Enter the weekly pounds.
- Read worm pounds first, then bin area.
- Bed 2/3 full with moist shredded paper.
- Bury food under 2 in; feed after prior food goes.
- Harvest castings in 3 to 6 months.
Formula
- scraps
- Kitchen scraps in lb per week.
- worms
- Red wigglers at 1 lb per 0.5 lb daily.
- area
- Shallow bin surface at 1 sq ft per lb.
Nebraska Extension stocks 1 lb per half-lb daily with 1 sq ft per lb; EPA counts 1 lb as ~1,000 worms eating ~25 % daily at startup.
Worked example
Example: 3.5 lb scraps a week
Defaults: 3.5 lb of scraps a week.
- Input: 3.5 lb scraps a week.
- Daily: 3.5 / 7 = 0.5 lb a day.
- Worms: 0.5 x 2 = 1 lb (about 1,000).
- Bin: 1 x 1 = 1 sq ft, 8 to 12 in deep.
- Tool shows 1 lb worms, 1 sq ft surface, feed 0.5 lb/day max.
Reference table
| Scraps/day | Worms | Bin |
|---|---|---|
| 0.25 lb | 0.5 lb (~500) | 0.5 sq ft |
| 0.5 lb | 1 lb (~1,000) | 1 sq ft |
| 1 lb | 2 lb (~2,000) | 2 sq ft |
| 2 lb | 4 lb (~4,000) | 2 x 2 ft |
Limits
- Red wigglers only. Nightcrawlers differ.
- Planning ratios; appetites vary by temp.
- Ignores citrus, onion, and meat limits.
- Apartment rules and fruit flies unmanaged here.
Common mistakes
- Overfeeding before prior food clears.
- Deep bins past 12 inches.
- Dry or soggy bedding extremes.
- Meat and dairy in the bin.
- Judging bins in week one.
Try it yourself
Quick checks. Answers sit tucked under each question.
7 lb scraps a week?
Daily 7 / 7 = 1 lb. Worms 1 x 2 = 2 lb (~2,000). Bin 2 sq ft.
1.75 lb scraps a week?
Daily 1.75 / 7 = 0.25 lb. Worms 0.5 lb (~500). Bin 0.5 sq ft.
Questions
How many worms do I need?
Scraps a day times 2. Half a pound daily needs 1 lb of red wigglers (about 1,000).
How big a bin?
One square foot per pound of worms. One pound fits a 1 x 1 ft bin 8 to 12 in deep.
How much do worms eat?
About 25 % of body weight daily per EPA; Nebraska stocks 1 lb per half-pound of garbage a day.
What bedding works?
Moist shredded newspaper or cardboard, fluffed 2/3 full, covered 2 in over each feeding.
What temperature and harvest?
59 to 77 F active, surviving 32 to 95 with deep bedding. Harvest castings in 3 to 6 months.
Can I use nightcrawlers instead?
No. Red wigglers live in the top inches; nightcrawlers burrow deep and suit soil, not bins.
Sources
- Cornell Composting: Worm Composting Basics
- EPA: Composting at Home (vermicomposting)
- Univ. of Nebraska-Lincoln: Vermicomposting Guide