Measuring stem diameter

Stem diameter under the Code

There are stem size restrictions that may apply to tree removal when thinning or clearing native vegetation.  

The Land Management (Native Vegetation) Code 2018 sets rules for clearing trees and shrubs. It uses diameter at breast height over bark (DBHOB) as a standard to determine which vegetation can be legally cleared.

Local Land Services can help you to understand your obligations when managing native vegetation, including advice on what trees should be retained. 

When to use stem diameter 

Your requirements for retaining trees of a certain size will vary according to the part of the Code that applies to your land and activities.  

To find out what DBHOB restrictions apply in your circumstances, read Managing native vegetation under the Land Management Code.

How to measure stem diameter 

Stem refers to the trunk of a shrub or tree. 

Diameter at breast height (DBHOB) is measured at 1.3 metres from the ground.  

• If there are multiple stems on a tree, the diameter is measured on the largest stem at this height.
• Measure DBHOB on the up-slope side of the tree

Sometimes it is not possible to measure at this height. 

If deformities or branches occur at 1.3 m, diameter should be measured at an equal distance above and below 1.3 m and the two measurements averaged. 

For trees forking at or just below 1.3 m, measure both stems above the fork and combine. 

For trees forking below 1.3 m, measure each stem and treat as two trees.

Measuring DBHOB using a forester’s tape 

A specially calibrated diameter tape, sometimes referred to as a forester’s tape, displays the diameter measurement when wrapped around the outside (circumference) of a tree stem. 

1. Determine ‘breast height over bark’ or 1.3 m above ground level using a standard tape measure and mark the height on the tree.
2. Wrap the forester’s tape around the girth of the tree at 1.3 m, making sure there are no twists in the tape.
3. Measure at right angles to the lean of the tree trunk.
4. The gradations on a forester’s tape do not start at the very end of the tape. Be sure to read the measurement from where the diameter scale begins. 

Measuring DBHOB using a string or rope 

If you don’t have a forester’s tape, you can still measure tree diameter using string or rope, a regular tape measure, and a calculator. 

1. With the measuring tape, measure 1.3m up the trunk of the tree from the ground and mark the height on the tree.
2. Wrap the string around the tree trunk at 1.3m, making sure the string is straight and tight around the trunk.
3. Cut or mark the circumference on the string.
4. Measure the length of the string using a standard measuring tape. This will give you the total circumference of the tree.
5. Divide the circumference by 3.14 to convert the circumference measurement to diameter.