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.