What it does
A tree’s wood is about half carbon, which came out of the air as CO₂. Weighing a tree is impractical, so foresters use allometric equations: formulas, fitted by cutting and weighing sample trees, that predict dry biomass from easy measurements such as the trunk diameter at breast height (DBH, 1.3 m up) and the height. This tool applies the equation you choose to a list of trees and works out:
- above-ground dry biomass from the equation;
- roots, as a root-to-shoot ratio times the above-ground biomass;
- carbon, as the carbon fraction of the total dry biomass;
- CO₂ equivalent, carbon × 44/12;
- yearly uptake, from the change since an earlier measurement, or by growing each trunk at a DBH growth rate for one year.
How to use it
- Trees. Paste or open one row per tree: a name (optional), DBH now in cm, height now in m, and if you have them the DBH and height at an earlier measurement. Give the years between the two measurements.
- Growth rate. For trees with no earlier measurement, give a typical DBH growth in cm per year to estimate the yearly uptake (the height is kept the same).
- Equation. Choose a × DBH^b or a × (ρ × DBH² × H)^b, where ρ is the wood density in g/cm³, and type its coefficients. Use an equation published for your species, region and size range: equations vary a lot, and using one outside its range can be badly wrong.
- Root-to-shoot ratio and carbon fraction. Typical values sit around 0.2 to 0.3 for roots and 0.47 to 0.5 for carbon, but use values from your own guidance.
The default coefficients are made-up illustrations, not taken from any study and not for any real species.
Worked example
The eight made-up trees, from a 14 cm cherry to a 51 cm pine, were measured now and five years ago. With the illustrative equation biomass = 0.1 × DBH^2.4, a root-to-shoot ratio of 0.25 and a carbon fraction of 0.47, they hold 5.23 t of dry biomass (4.18 t above ground and 1.05 t in roots). That is 2.46 t of carbon, or 9 t of CO₂e. Comparing with the earlier measurements, they took up 346 kg of CO₂e per year. The biggest store is Pine 1, with 2.7 t CO₂e, 30 % of the total.
FAQs
Why is my result so different with another equation? Biomass grows steeply with diameter (b is often 2 to 2.7), so small changes in the coefficients change the result a lot. Always use an equation built for trees like yours.
Can I use this to sell carbon credits? No. Carbon credit standards set their own methods, sampling, uncertainty deductions and checks. This tool is for learning, planning and rough estimates.
Does it count dead wood, leaves or soil? It counts what your equation counts (usually stem, branches and leaves) plus roots. Dead wood, litter and soil carbon are not included.
Is my data uploaded? No. Everything runs in your browser.
Where the numbers come from
- Allometric biomass equations of the forms a·DBH^b and a·(ρ·DBH²·H)^b, root-to-shoot ratios and the carbon fraction of dry biomass: standard forest inventory methods. The tool has no built-in species equations; the default a, b, wood density, root-to-shoot ratio and carbon fraction are made-up illustrations.
- CO₂ from carbon by the ratio of molar masses, 44.01/12.01.
- Checked in the tests against an independent NumPy calculation. The example trees are made up.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-09.