How long would one tree need to grow?
Type in an amount of CO₂. You get back the time a single tree needs, on average, to take it out of the air again.
One tree would need about 4 weeks to bind this.
0.08 tree years · 0.8 kg CO₂ ÷ 10 kg per tree yearTake it with you
Show the tree wherever the CO₂ number appears. The badge carries its icon and style inside and loads nothing from anywhere.
Why count in years instead of kilograms?
Nobody has ever held a kilogram of CO₂. Is that a shoebox full? A whole house? Is it a lot or almost nothing? CO₂ is a gas we never touch in daily life, so a number in kilograms or tonnes stays abstract. We read it and move on.
Time is different. Everyone knows what a month feels like, or twenty years. And when a single tree would need longer than a human life, you start to ask whether the damage can be undone within your own lifetime at all.
That is the whole idea. Tree Years translates a number you cannot picture into a span of time you already know.
A few everyday examples
| What | CO₂ | Tree years | One tree would need |
|---|
The unit
One tree year is the amount of CO₂ a single tree binds in one year. We use a round 10 kg. Real trees bind more or less depending on species, age, location and season, so this is a reference value for understanding, the way a horsepower is.
Use it anywhere. On a product page, in a travel app, in a report, in a post.
const treeYears = kgCO2 / 10;
Free to use, no permission or credit needed. Dedicated to the public domain under Creative Commons CC0 1.0 Universal.
Why a straight line
A young tree binds almost nothing. For years it is small, without protective bark, easy to eat or trample. Then it gains strength and grows, and every year it adds more wood than the year before. A large tree can add as much mass in one year as a whole small tree weighs.1 Growth means taking CO₂ out of the air.
A typical beech, 23 metres tall, binds about one tonne of CO₂ in trunk and roots over roughly 80 years.2 The average of its curve is simple: total CO₂ divided by years. 1,000 kg in 80 years is 12.5 kg a year. In its early years the real tree binds less than that average, later more. Over its whole life the two meet.
Tree Years rounds down to 10 kg and draws a straight line, because people think in straight lines.
How much a tree binds depends on many things:
- species
- age
- location
- soil
- water
- climate
- season
- neighbouring trees
Foresters estimate it from trunk diameter and height. That gives the dry mass of the tree. About half of it is carbon, and every kilogram of carbon was once 3.67 kg of CO₂ in the air.
Where the 10 kg comes from
Published figures for one tree range from about 6 kg a year for a young city tree to more than 20 kg for a mature one. 10 kg sits between them, a little below the lifetime average of a beech.
We round down on purpose. That way Tree Years never overstates what a tree can do. If anything, a tree in your forest is faster than the unit says.
The Tree Years badge
Wherever a CO₂ figure appears, put the tree next to it. Set your amount in the calculator at the top and copy the code. It contains everything, the icon included, and loads nothing from anywhere. The badge links back to treeyears.org, so others can find the unit too.
Prefer plain text? Just write the sentence. Change the number, keep the tree.
0.8 kg CO₂ = 4 weeks of tree growthThe Tree Years icon is free to use under CC0 1.0. Download the icon as SVG.
And what happens to the tree afterwards?
We were asked this every time we talked about trees and CO₂. It is the right question. A tree holds its carbon only as long as its wood exists.
It falls and rots
Dead wood decomposes and most of the CO₂ goes back into the air, slowly, over years or decades. Part of the carbon stays in the forest soil.
It burns
Fire, or a stove, releases the stored CO₂ within minutes.
It becomes a house
Wood used in buildings and furniture keeps its carbon for as long as the building stands, often a hundred years or more.
Forests can tip
Between 2017 and 2022, drought and bark beetles made the German forest a net source of carbon for the first time in decades.3 More was lost than grew back.
Whether a tree needs 2 days or 2.2 days does not change how it feels.
All of this is real and all of it matters. Tree Years is not meant to be an exact measure. It is a simplified unit with some blur on purpose, so you can develop a feeling for an amount of CO₂ and for what everyday emissions mean.
What Tree Years is, and what it is not
A way to understand
Tree Years makes an amount visible. It is not a way to buy yourself free. Planting trees does not cancel out emissions, and many offset schemes promise more than they deliver.
One tree, on purpose
One tree for 100 years binds the same as 100 trees for one year. We tell it as one tree because a lifetime is something you can feel. A forest is not.
Rounded, on purpose
Emission figures are estimates, and so is 10 kg per tree, an average we chose so everyone can calculate with it. The examples on this page are typical values. Use precise figures for your own case where you have them.