Compost C:N ratio calculator
PROWeighted C:N ratio of your compost mix. Target 25–30:1.
Short answer: Mix C:N = Σ(weight × material C:N) ÷ total weight. 60 lb browns (C:N 60) + 20 lb greens (C:N 15) = 48.75 : 1 (too many browns). Enter your measurements above and the compost c:n ratio calculator returns the quantity, unit conversions and an estimated cost instantly, in imperial or metric — no sign-up needed.
What do you need to measure?
What is the answer?
Mix C:N
48.8 : 1
target 25–30:1
Total weight
80 lb
% browns
75.00%
How does the compost c:n ratio calculator work?
Mix C:N = Σ(weight × material C:N) ÷ total weight.
What does a worked example look like?
60 lb browns (C:N 60) + 20 lb greens (C:N 15) = 48.75 : 1 (too many browns).
What do people ask most?
›Why 25–30:1?
Microbes decompose fastest in that range; higher = slow, lower = smelly.
Which garden calculator should you use next?
Where can you learn more?
Read field notes on estimating and materials, or browse every calculator we make.
What should you read before you order materials?
Field notes from real jobs that explain the numbers behind this calculator.
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