How many trees do I need to plant to offset my emissions?
As trees grow, they capture CO2 from the atmosphere. It is not enough to plant a tree; you must also wait for it to grow! You can see an estimation of trees and time needed if you place your mouse over the displayed amount of CO2 for a few seconds. But remember, it is much better to avoid and reduce emissions, than to offset them. You should also know that the effectiveness of tree-planting offsets is controversial.
How are the number of trees and their growth time estimated?
It is assumed that it takes in average one year for a single tropical tree to capture 22kg of CO2 from the atmosphere. This assumption is taken from Wikipedia. If you know a better value, please let me know and correct Wikipedia.