Calculation Result
Choose a mode, enter values, then calculate.
Calculation steps and assumptions
No calculation has been completed.
Formula Used
Material volume is converted into mass using bulk density. Dry mass then estimates carbon and nitrogen contributions. The weighted mixture ratio compares total carbon with total nitrogen.
Pile volume depends on the selected geometric shape. Finished yield applies the entered shrinkage percentage. Garden demand multiplies area by application depth.
Weighted C:N = Total estimated carbon ÷ Total estimated nitrogen Rectangular volume = Length × Width × Height Cylindrical volume = π × Radius² × Height Conical volume = (π × Radius² × Height) ÷ 3 Finished volume = Starting volume × (1 − Shrinkage fraction) Garden compost volume = Garden area × Application depth
How to Use
Select the calculation mode that matches your planning task. Enter realistic material, dimension, or moisture values. Review every warning before changing your compost recipe.
Use the example buttons to load practical ingredient mixtures. Adjust densities when your materials are tightly compacted. Export the final summary for later reference.
Example Compost Data
| Material | Type | Typical C:N | Typical moisture | Planning note |
|---|---|---|---|---|
| Fresh grass clippings | Green | 17:1 | 75% | Mix with bulky browns. |
| Vegetable scraps | Green | 15:1 | 88% | Drain excess liquids. |
| Dry leaves | Brown | 60:1 | 15% | Shred for faster breakdown. |
| Straw | Brown | 80:1 | 12% | Add water while mixing. |
| Sawdust | Brown | 350:1 | 10% | Use small quantities. |
Composting Guidance
A practical hot pile often targets about 25:1 to 30:1. Moisture should resemble a wrung-out sponge. Adequate air prevents unpleasant anaerobic conditions.
Avoid treated wood, glossy paper, oils, chemicals, pet waste, and diseased plants. Local composting rules may restrict additional materials. Always follow local safety guidance.
Frequently Asked Questions
What is a good compost C:N ratio?
Many active piles perform well near 25:1 to 30:1. Wider ratios can still decompose. They usually require more time.
Why does the calculator use moisture?
Fresh materials contain substantial water. Dry mass better represents available carbon and nitrogen. Moisture also affects microbial activity.
Can I enter materials by volume?
Yes, volume converts using an estimated bulk density. Loose materials vary greatly. Edit density when better data exists.
What happens when compost is too wet?
Air spaces can collapse inside the pile. Odours may develop quickly. Add dry, absorbent, bulky browns.
What happens when compost is too dry?
Microbial activity becomes slower. Add water gradually while turning. Avoid creating saturated pockets.
How accurate is the finished yield?
It is an estimate based on shrinkage. Materials decompose at different rates. Actual yield depends on management.
How large should a hot pile be?
A pile near one cubic metre often retains heat. Smaller piles can still compost. They may remain cooler.
Can this calculate bag quantities?
Yes, application mode calculates total volume. It divides demand by bag size. The result rounds upward.
Does turning always speed composting?
Turning usually improves oxygen distribution. Excessive turning may release heat. Balance aeration with moisture retention.
Limitations and Assumptions
Material values are typical planning estimates. Real composition changes with age and storage. Laboratory analysis gives more precise results.
Decomposition time is a practical estimate, not a guarantee. Climate and particle size matter greatly. Observe pile temperature and odour.