Tumbler Capacity Calculator
Created by: Emma Collins
Last updated:
Estimate total and usable compost tumbler volume from dimensions and operational fill target. Plan throughput and batch timing from weekly input rates.
Tumbler Capacity Calculator
CompostingCalculate total and usable compost tumbler volume
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What is a Tumbler Capacity Calculator?
A tumbler capacity calculator estimates internal volume and recommended usable fill for compost tumblers. It helps you understand how much material your system can process while preserving aeration and rotation efficiency.
Capacity planning is essential for avoiding overfill, scheduling feedstock intake, and deciding whether one chamber is enough for your weekly waste stream.
Tumbler Capacity Formulas
Cylindrical volume: π × r² × length
Unit conversion: 1 cubic foot = 7.48 gallons
Usable fill: Total Volume × Fill Percentage
Recommended fill range: 60% to 75%
Example Calculation
For a tumbler 30 inches diameter and 28 inches long at 70% fill:
- Total volume ≈ 11.4 ft³ (about 85 gallons)
- Usable volume ≈ 8.0 ft³ (about 60 gallons)
- If weekly input is 10 gallons, fill time ≈ 6 weeks
- Recommended operation: keep headspace for tumbling efficiency
Common Applications
- Equipment selection: Compare tumbler models by usable capacity.
- Workflow planning: Match weekly inputs to chamber volume.
- Dual-chamber scheduling: Alternate active and curing sides.
- Troubleshooting: Diagnose poor mixing from overfilled chambers.
Tips for Better Tumbler Performance
- Keep fill below the maximum line for reliable rotation.
- Balance wet kitchen scraps with dry browns to avoid clumping.
- Rotate consistently on schedule rather than sporadically.
- Use a second chamber or staging bin for continuous input systems.
Frequently Asked Questions
How do I calculate compost tumbler capacity?
For cylindrical tumblers, capacity is based on π × radius² × length. Convert that internal volume into cubic feet or gallons for practical planning. This calculator also estimates a recommended max fill level, since tumblers should not be filled to 100% if you want effective tumbling and aeration.
What is the best fill level for a compost tumbler?
Many tumblers work best around 60% to 75% full. Lower fill can reduce mixing efficiency, while overfilling limits movement and airflow. A controlled fill level gives better oxygen transfer, more consistent moisture distribution, and easier rotation.
Why does overfilling a tumbler slow composting?
Overfilling reduces free space needed for material turnover and oxygen exchange. It can create compact, wet zones where decomposition slows or turns anaerobic. Keeping space for movement helps maintain microbial activity and more even decomposition across the batch.
Can this calculator help with weekly feed planning?
Yes. By estimating usable fill volume and weekly input, you can approximate fill duration and decide whether you need a dual-chamber or multi-tumbler setup. This helps prevent bottlenecks where one chamber is full before prior material is cured.
Do dual-chamber tumblers need separate capacity calculations?
Yes. Each chamber should be calculated and managed independently unless the product specifies true shared internal volume. This calculator can be run per chamber so your feed and turning schedule stays realistic for each side of the system.
Sources and References
- Composting equipment guides for tumbler operation and fill levels.
- Extension composting resources on aeration and container management.
- Practical composting manuals for rotational systems and throughput planning.