Compost Bin Calculator

A 3×3×3 ft three-sided bin holds about 27 cubic feet (202 gallons) of compost and needs 4 posts and 9 slat boards — enter your bin's size to get capacity and a materials list.

Side length (ft)

Height (ft)

Slatted sides

Slat width (in)

Airflow gap (in)

Board stock length (ft)

Capacity

27 ft³

Posts

Boards

Corner posts (3.5ft)
4 pcs
per pc for Corner posts (3.5ft)
Slat boards (8ft)
18 slats total
9 boards
per board for Slat boards (8ft)
Corner brackets
4 pcs
per pc for Corner brackets

Enter your local prices to see an estimated cost.

How we calculate this

Capacity = side length² × height. Slats per side = bin height ÷ (slat width + airflow gap), rounded up, multiplied by your number of slatted sides to get total slats. We convert total slat length to boards using your stock board length, rounded up — you can always trim a board, never stretch one.

Estimates only. Check local codes and product labels. Read our full disclaimer.