Compost Ratio Calculator
Balance your greens and browns perfectly. Aim for a C:N ratio of 30:1 for the fastest compost.
Ingredients
PartsEnter materials to see the ratio
The Science of Rot
Composting isn't just throwing trash in a pile; it's farming microbes. These microscopic workers need a balanced diet of "Browns" (Carbohydrates for energy) and "Greens" (Protein for growth).
Get the balance right (30:1), and your pile will heat up to 140°F+, killing weed seeds and pathogens. Get it wrong, and you get a slimy, smelly mess.
Why Use This Calculator?
Perfect Balance
Hit the elusive 30:1 ratio every time for faster, hotter compost.
Custom Materials
Add your own unique ingredients like Seaweed or Sheep Manure.
Material Database
Pre-loaded C:N values for common items like Coffee, Straw, and Cardboard.
Problem Solver
Instantly diagnose if your pile is too Nitrogen-heavy (smelly) or Carbon-heavy (slow).
Save Recipes
Download your successful mix formulas to repeat next season.
Visual Gauge
See exactly where your mix falls on the spectrum from 'Rot' to 'Dry'.
How to Use the Calculator
- Inventory: Look at what waste you have. A bag of leaves? A bucket of kitchen scraps?
- Input Materials: Select the items from the dropdown lists. Use "Custom" if yours isn't there.
- Estimate Volume: Enter "Parts". This can be anything: Buckets, Shovels, or Wheelbarrows.
- Calculate: Click the button to see your C:N ratio.
- Adjust: If the gauge says "Too Green", add more Brown parts until it hits the blue zone.
Real-World Example
You mowed the lawn and have 2 bags of Grass Clippings (Green). You also have a pile of Dry Leaves (Brown). How many leaves do you need to balance the grass?
Common C:N Ratios
Frequently Asked Questions
Why is 30:1 the ideal ratio?
Composting bacteria need 30 parts Carbon for energy to consume 1 part Nitrogen for protein. This perfect balance allows them to work fastest, generating heat and breaking down material quickly.
What counts as a 'Green'?
Greens are Nitrogen-rich materials. Think: Vegetable scraps, fruit peels, fresh grass clippings, coffee grounds, tea bags, and animal manure (chicken/cow).
What counts as a 'Brown'?
Browns are Carbon-rich materials. Think: Dry leaves, cardboard, shredded newspaper, straw, sawdust, wood chips, and pine needles.
Can I compost citrus peels?
Yes, but in moderation. The acidity can slow down decomposition if you add too much at once. Chop them small and mix with plenty of browns.
Can I compost meat or dairy?
No, avoid meat, dairy, oil, and bones in standard backyard piles. They attract pests (rats/raccoons) and smell terrible. They require specialized high-heat systems.
Why does my compost smell bad?
It likely has too much Nitrogen (too many wet greens) and has gone anaerobic. Flip the pile to add air and mix in a large amount of dry Browns (leaves/cardboard) to absorb moisture.
How long does composting take?
With a perfect 30:1 ratio and frequent turning ('Hot Composting'), it can be ready in 3-6 months. Passive 'Cold Composting' (just piling it up) takes 6-12 months.
Is printed cardboard safe?
Most modern cardboard and newspaper use soy-based black inks which are safe. Avoid glossy, shiny magazine paper or plastic-coated cardboard.
Do I need a compost starter?
Not really. The bacteria are naturally present on the leaves and food scraps. A shovel full of garden soil or finished compost added to a new pile works just as well.
What if I don't know the exact C:N ratio of my material?
Use our 'Custom Material' feature! You can research the approximate C:N value online (e.g., 'C:N ratio of seaweed') and add it to get a more accurate calculation.
More Plant Care Tools
Master your indoor jungle with these essential calculators: