Tree CO₂ Sequestration Calculator
How much carbon dioxide a tree (or a planting) absorbs per year and over its life from trunk diameter or age and species type — with the biomass method, tonnes offset and equivalent car miles.
How it works
biomass = 0.4·π(d/2)²·h × wood density × 1.2 (roots); carbon = 50% of dry biomass; CO₂ = C × 44/12; planting: ~20–35 kg CO₂ per tree per year
A tree is roughly half carbon by dry weight, so estimating its wood volume gives the CO₂ it has pulled from the air (multiply carbon by 44/12). Mature trees hold a tonne or more; a new sapling absorbs almost nothing for years, then 20–35 kg a year through mid-life, which is why “plant a tree to offset a flight” claims need decades to come true. Uptake stops being an offset if the tree is cut and burned. Species, climate and soil move these numbers by a factor of two either way.
Worked example
A 30 cm, 15 m hardwood: volume 0.42 m³, dry mass 0.25 t (0.30 t with roots), 0.15 t carbon → 0.56 t CO₂ stored, about 15 kg absorbed per year — the emissions of 40 miles of driving.
Frequently asked questions
How many trees offset a person’s emissions?
At ~25 kg CO₂ per tree per year, a 5-tonne footprint needs about 200 growing trees — permanently.
Do forests keep absorbing forever?
Mature forests reach a rough balance where decay equals growth; the big uptake happens during the growing decades.
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This calculator is for educational purposes. Double-check important results before acting on them.