The Calculation Chain
| Step | Calculation |
|---|---|
| 1. Stem biomass | Volume (m³/ha) × wood density (t/m³) |
| 2. Above-ground biomass | Stem biomass × biomass expansion factor (branches, bark, foliage) |
| 3. Below-ground biomass | Above-ground × root-to-shoot ratio |
| 4. Total biomass | Above-ground + below-ground |
| 5. Carbon | Total biomass × carbon fraction (IPCC default 0.47) |
| 6. CO₂ equivalent | Carbon × 44/12 (the mass ratio of CO₂ to C) |
Every step carries uncertainty, and they compound. Wood density varies within a species; expansion factors vary with age and stocking; root-to-shoot ratios are among the least well-measured numbers in forestry.
Choosing the Inputs
| Input | Typical range | Note |
|---|---|---|
| Wood density (oven-dry) | 0.35 – 0.75 t/m³ | Eucalyptus ~0.55, pine ~0.45, teak ~0.60, light hardwoods lower |
| Biomass expansion factor | 1.15 – 1.6 | Higher in young, branchy stands; lower in closed, well-formed ones |
| Root-to-shoot ratio | 0.20 – 0.30 | Higher on dry sites where trees invest in roots |
| Carbon fraction | 0.45 – 0.50 | IPCC default 0.47 |
What This Number Is Not
Four things it cannot do
- It is not a carbon credit. Credits require an approved methodology, a validated baseline, additionality, permanence, leakage accounting and independent verification.
- It is a stock, not a flow. It estimates carbon standing now — not annual sequestration, and not net of what the land held before.
- It ignores soil carbon, litter and deadwood, which can be a large share of a forest's total.
- It ignores what happens at harvest. Carbon in a pole that becomes a fence post behaves differently from carbon in firewood.
If you are being offered a carbon deal on the strength of a number like this one, read carbon credit eligibility first — particularly the section on red flags.
Frequently Asked Questions
How much CO2 does a hectare of trees store?
It depends on standing volume, species density and stand age, so there is no single figure. A young plantation stores a fraction of what a mature one does.
The chain is: volume × wood density gives stem biomass; expansion factors add branches, bark and roots; multiply by 0.47 for carbon; multiply by 44/12 for CO₂e. Use the calculator above with your own volume figure.
Is this the same as a carbon credit?
No, and this distinction matters. A credit requires an approved methodology, a validated baseline, demonstrated additionality, permanence arrangements, leakage accounting and independent third-party verification.
This calculator estimates carbon standing in biomass. It is for planning and education only and must never be used to claim, sell or offset carbon.
Why do I need a biomass expansion factor?
Because merchantable volume only counts the stem. Branches, bark, foliage and roots also hold carbon, and the expansion factor scales stem biomass up to the whole tree.
It varies with age and stocking — young branchy stands have higher factors than closed, well-formed ones.
What carbon fraction should I use?
0.47 is the IPCC default and a reasonable choice for most species. Values in the literature generally sit between 0.45 and 0.50.
The uncertainty in this parameter is small compared with the uncertainty in volume, density and expansion factors.
Does the calculator include soil carbon?
No. It covers above-ground and below-ground biomass only. Soil organic carbon, litter and deadwood are excluded, and in some forest types soil carbon exceeds biomass carbon.
That omission is one reason this number should not be used for any accounting purpose.