The age of old trees can be estimated by measuring their circumference (girth), and applying a small calculation.
Different trees grow at different rates, and the calculation gives an approximate age only.
Using a tape measure or ruler, measure 1.5 metres from the ground.
Then from this point, measure the girth (circumference) of the tree in centimetres.
Trees grow at different speeds with the circumference increasing at an average of 2.5cm a year. The figures below show the rate at which different trees grow:
- Holly, Yew: 1.25cm / year
- Oak: 1.88cm / year
- Ash, Beech, Elm, Hazel: 2.5cm / year
- Sycamore: 2.75cm / year
- Pine, Spruce: 3.13cm / year
Use these figures to calculate the age of your chosen trees:
- Divide the circumference by the growth rate for your tree. A calculator may help!
For example, if your chosen tree is an oak tree that measures 110cm, you would need to do the following sum: 110 / 1.88 = 58.5 years (approximate!)
An oak tree would need a girth of about 900cm (9 metres) to have dated from the time of Henry VIII - (900 / 1.88 = 480 years: c1530).