Practical guides
DBH means diameter at breast height
DBH means diameter at breast height. The measuring height and multi-stem method come from your municipality.
DBH meaning: diameter at breast height
DBH stands for diameter at breast height. Municipal tree bylaws use DBH as a repeatable way to decide whether a tree crosses a size threshold for protection, permits or construction setbacks.
The phrase sounds universal, but the exact measuring height is not. Toronto and Vancouver measure at 1.4 m above ground, while New Westminster uses 1.3 m above grade. Always use the local rule.
How to calculate DBH from circumference
If you wrap a normal tape around the trunk, you measured circumference, not diameter. Convert it with this formula:
Example: a trunk circumference of 94.2 cm is about 30 cm in diameter. A forestry diameter tape performs this conversion automatically.
Where to measure the trunk
Measure at 1.4 m above ground. Toronto’s general private-tree threshold is 30 cm DBH.
Measure at 1.4 m above ground. Vancouver requires a permit to remove a private-property tree 20 cm or greater in diameter, subject to the bylaw’s details and exceptions.
Measure at 1.3 m above grade. Protected-tree rules include trees 20 cm or greater and a specific multi-stem method.
Those examples show why a generic “measure at chest height” instruction is not enough for a permit decision.
How to measure a multi-stem tree
- Do not invent a formula.
- Municipalities can define multi-stem trees differently.
- Toronto uses the largest stem when calculating a Tree Protection Zone and protects the tree where at least one stem reaches the protected threshold.
- New Westminster says to add the diameters of the two largest stems for its protected-tree definition.
Slopes, forks and unusual trunks
Buttress roots, leaning trunks, forks near the measurement point and changes in grade can make a measurement ambiguous. When a tree is close to a permit threshold, photograph the measurement and confirm the municipality’s method or ask a qualified arborist.
Why DBH accuracy matters
A small difference can change whether a size-based rule applies and can also change a construction protection distance. Toronto, for example, uses DBH bands to set minimum Tree Protection Zone distances around protected trees.
For local examples, see Toronto tree protection zones and permits, Vancouver tree removal rules and New Westminster tree permits.
Official sources
Sources linked for independent re-check. Rules can change and the exact property/tree can change the answer. Confirm the current municipal requirement before work begins.
Independent information, not legal or arboricultural advice. Ownership, site conditions and professional assessments can change the answer.