Tree CO2 Sequestration Calculator
Trees remove carbon dioxide from the air through photosynthesis and store the carbon in their wood, leaves and roots. This calculator estimates how much carbon dioxide a given amount of tree biomass represents. The method follows the standard carbon accounting chain: take the oven-dry biomass, multiply by the carbon fraction (about half of dry wood is carbon) to find the stored carbon, then multiply by the ratio of the molecular weight of carbon dioxide to carbon, 44 divided by 12, to find the carbon dioxide that was pulled from the atmosphere. You enter the dry biomass, the carbon fraction and the conversion factor, and the tool returns the stored carbon and the sequestered carbon dioxide, computed deterministically from the formula shown below, never estimated, so the worked example reconciles exactly with the figures on screen. The carbon fraction and the molecular ratio are left editable so you can use species-specific values. Keep in mind that dry biomass is the weight after moisture is removed, much less than a living tree's green weight, and that this figure measures carbon held in the biomass you enter, not a full life-cycle benefit. Use this tool to estimate the carbon stored in a tree or stand.
Sequestered carbon dioxide is dry biomass x carbon fraction x (44 / 12). For 1,000 kg of dry biomass at a carbon fraction of 0.5, the tree stores 500 kg of carbon, equal to 1,833.35 kg of carbon dioxide.
Carbon sequestration formula
carbon = dry biomass x carbon fraction
CO2 = carbon x (44 / 12)
carbon fraction = about 0.5 of dry biomass
44 / 12 = ratio of CO2 to carbon molecular weight (about 3.667)
Multiplying dry biomass by the carbon fraction gives the carbon locked in the tree. Scaling that carbon by 44 divided by 12 converts it to the mass of carbon dioxide removed from the atmosphere, because each carbon atom captured came from one carbon dioxide molecule.
Worked example
A tree holds 1,000 kg of dry biomass, with a carbon fraction of 0.5.
- Carbon stored = 1,000 x 0.5 = 500 kg
- CO2 = 500 x 3.6667 = 1,833.35 kg (using the default ratio of 3.6667; the exact 44 / 12 gives 1,833.33 kg)
The biomass represents about 1,833.33 kg of carbon dioxide stored. These are the calculator's default inputs, so the result above matches the widget exactly.
Tree CO2 sequestration: frequently asked questions
How does a tree sequester carbon dioxide?
Through photosynthesis a tree pulls carbon dioxide from the air and locks the carbon into wood, leaves and roots as biomass. About half of a tree's dry weight is carbon. When that carbon is multiplied by the ratio of the molecular weight of carbon dioxide to carbon, you get the mass of carbon dioxide removed from the atmosphere.
Why multiply carbon by 44 over 12?
Carbon has an atomic weight near 12, and carbon dioxide has a molecular weight near 44 (one carbon plus two oxygen atoms). Each unit of carbon stored corresponds to 44 divided by 12, about 3.667, units of carbon dioxide that were removed from the air. That ratio converts stored carbon into sequestered carbon dioxide.
What carbon fraction should I use?
A widely used default is that carbon makes up about 50 percent of a tree's oven-dry biomass. The exact fraction varies a little by species and tissue, so this calculator leaves it editable. If you have a species-specific value, enter it; otherwise 0.5 is a reasonable general estimate.
Is dry biomass the same as the weight of the tree?
No. Dry biomass is the weight after moisture is removed. A living tree contains a large amount of water, so its green weight is considerably higher than its dry weight. Carbon accounting uses oven-dry biomass, which is why this tool asks for dry weight rather than fresh weight.
Is this an exact measure of climate benefit?
It is an estimate of carbon stored in the biomass you enter, not a full life-cycle figure. Real sequestration depends on growth rate, decay, soil carbon and what eventually happens to the wood. Treat the result as an order-of-magnitude guide and use measured inputs for serious accounting.
Official sources
- Carbon cycle and carbon dioxide reference: US National Oceanic and Atmospheric Administration (NOAA). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.