Compost Bin Volume Calculator

Example data table

Formula used

• Rectangular: V = L × W × H_eff
• Cylindrical: V = π × r² × H_eff
• Tapered rectangular (frustum): V = (H_eff/3) × (A_top + A_bot + √(A_top×A_bot))
• H_eff = max(0, H − freeboard)
• Total = V × fill% × (1 − settling%) × bins

How to use this calculator

1. Select the bin shape that best matches your compost container.
2. Choose the unit you used to measure the bin dimensions.
3. Enter inside measurements for better accuracy.
4. Set freeboard to keep turning space and prevent spills.
5. Adjust fill level and settling to match your compost style.
6. Press Calculate Volume to see totals and download reports.

Planning capacity with real measurements

Compost systems work best when bin capacity matches your expected inputs. Measure internal length, width, and height so the calculated space reflects usable volume, not exterior lumber thickness. Adding freeboard prevents overfilling and leaves room for turning, aeration, and moisture checks during active decomposition. For indoor buckets or kitchen caddies, small errors add up quickly, so recheck measurements after fitting liners or screens. Record values so you can replicate sizing when upgrading later easily.

Choosing the right shape model

Many backyard bins are rectangular, while tumblers and barrels are cylindrical. Some manufactured bins taper toward the base to improve stability and drainage. Selecting the correct geometry helps you avoid underestimating capacity, especially when the bottom area is much smaller than the opening. If your bin has rounded corners, the rectangular option still works when you measure the span and accept a small safety margin.

Understanding fill level and settling

Fresh scraps and dry browns create voids that collapse as material breaks down. Fill level represents how full you typically load the bin, while settling reduction represents early shrink during heating. Using both parameters produces a practical working capacity for weekly additions and turning cycles. Higher settling values are common when you shred inputs, add water, or compress layers, while lower values fit coarse yard waste and chunky bulking agents.

Interpreting outputs across common units

The calculator reports totals in liters, cubic meters, cubic feet, cubic yards, and US gallons. Liters help compare standard composters, cubic feet align with garden bed planning, and cubic yards support bulk amendment estimates. Use the converted table to match how you buy materials locally each season.

Using results to improve compost performance

Aerobic composting benefits from adequate mass, balanced carbon and nitrogen, and consistent moisture. If capacity is too small, piles cool quickly and require frequent attention. If capacity is too large, mixing becomes difficult. Use the computed volume to scale inputs, select tools, and plan a two-bin rotation.

FAQs

1) Should I measure inside or outside dimensions?

Use inside dimensions whenever possible. Outside measurements include wall thickness, which can overstate capacity and affect turning space, aeration volume, and realistic weekly loading.

2) What is a good freeboard setting?

A small freeboard, often 5–10 cm or 2–4 in, keeps material from spilling while turning and allows room for mixing, moisture checks, and adding fresh inputs.

3) How do I choose settling reduction?

Start with 10–20%. Use higher values for shredded, wetter, or compressed mixes. Use lower values for coarse leaves, wood chips, or bulky materials that hold structure longer.

4) Why does the calculator ask for fill level?

Most bins are not filled to the brim in real use. Fill level models your typical loading so the reported capacity matches your working routine.

5) Can I use this for multiple bins?

Yes. Set the number of bins to get a combined capacity. This helps plan two-bin rotations, curing space, and seasonal input surges.

6) Which unit should I use for garden planning?

Use cubic feet for bed amendments and mulch estimates, liters for standard composters, and cubic yards for bulk deliveries. The conversions table lets you switch quickly.