How to calculate how much carbon dioxide your tree has taken from the atmosphere

Posted by Jason Ramsdale on 9 December 2015 at 2:05 pm

The amount of mass that is carbon within a tree is approximately 50%. To calculate how much CO2 this represents, times your carbon by 3.6. Now to the hard bit - WARNING - this involves maths!

Calculating the amount of carbon sequested by a tree is a tricky business - the species, location and age of the tree all play a part. That said, there is a way to estimate how much carbon is stored in a tree.

The following is a step by step guide to calculating how much carbon is stored in a tree. The figures [in brackets] are from Ecometrica's one tonne tree example.

1. Measure around the circumference of the tree’s stem (trunk) 1.3 metres up from the ground [1.63 m].

2. Divide the circumference by Pi (π = 3.142) to get the diameter [0.52 m].

3. Half the diameter to get the base radius (b) [0.26 m].

4. Measure or estimate the radius at the top of the stem (t) [0.2 m].

5. Estimate the height of the stem (h) [12 metres]. There are several fun (and safe!) ways to do this here.

6. Once we have these measurements we can work out the volume (v) of the stem using this calculation [We show how we used this calculation at the bottom]:

So for our example tree the volume of the stem would equal around 2 m3.

7. To work out the mass of the stem, multiply the volume by the density. For our example tree the density is 620 kg/m3. So, the mass of the stem is around 1.243 kg or 1.2 tonnes.

8. To work out the mass of the rest of the tree we use the ratio given by Ecometrica. The stem = 62% of the tree. So, 1.2 tonnes ÷ 62 × 100 gives a total mass of the tree at approximately 2 tonnes.

9. The amount of mass that is carbon within a tree is approximately 50%. So for our example tree we have 1 tonne of carbon locked up.

10. To calculate how much CO2 this represents we just need to know that each atom oxygen weighs roughly 33% more than each carbon atom and for each carbon atom we need two oxygen atoms. So roughly, carbon x 3.6 = CO2.

Our example tree has taken 3.6 tonnes of carbon dioxide from the atmosphere.

Working out stem volume:

Image: Ecometrica.

Need help with any Jargon?