How to use this calculator
- Enter or choose soil organic carbon.
- Enter or choose bulk density.
- Enter or choose layer depth.
- Enter or choose stones and gravel (optional).
- Enter or choose area.
- The carbon stock updates as you type. Use Copy result or Share to keep it.
Method
SOC stock (t C/ha) = SOC % × Bulk density (g/cm³) × Depth (cm) × (1 − Coarse fraction); CO₂e = C × 44 ÷ 12
- SOC %
- organic carbon by mass of fine soil
- Bulk density
- dry mass per volume of soil
- Coarse fraction
- stones and gravel share of the volume
- 44/12
- mass ratio of CO₂ to C
Worked example
- Stock = 1.2 × 1.35 × 30 × 0.95 = 46.17 t C/ha.
- CO₂e = 46.17 × 44 ÷ 12 = 169.29 t/ha; over 10 ha, 461.7 t C.
The top 30 cm holds about 46 t of organic carbon per hectare, equivalent to 169 t of CO₂.
What the result means
To compare stocks over time or between practices, sample to the same depth, or better, compare equal soil masses, because tillage and compaction change bulk density.
Assumptions and limits
- SOC and bulk density are averages for the whole layer.
- A single estimate is not a verified carbon credit; carbon schemes set their own sampling and measurement rules.
- If you only have organic matter %, a conversion factor is needed, and it varies between soils.
Questions
Why multiply by 44/12?
A CO₂ molecule weighs 44 units and its carbon atom 12, so 1 t of carbon corresponds to 3.67 t of CO₂.
Can I sum several layers?
Yes. Calculate each layer with its own carbon %, bulk density and depth and add the stocks.