Tree calculators
Work out the zone before you call
One calculator built on AS 4970:2025, the current edition, entered from whichever figure you came for. It will give you a number and it will also tell you what that number is not — which is most of the value.
0415 105 592Call 0415 105 592or send the address across
The three
Start where you are
Each opens the same tool at the figure you came for, and your measurements carry across.
TPZ / NRZ calculator
Notional root zone radius and area, from trunk diameter at 1.4 metres. Handles multi-stemmed trees.
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SRZ calculator
Structural root zone radius, from the diameter above the buttress flare.
Read more
NRZ encroachment calculator
Give the distance from the trunk to the works. Classifies as minor, moderate or major.
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A calculated zone is a starting point
These calculators implement the rules Adam supplied, against AS 4970:2025 — the current edition. They are useful for understanding the scale of what you are dealing with before a conversation, and for checking a figure someone has given you.
What none of them produce is a Tree Protection Zone. The notional root zone is the calculated starting point; the final TPZ is determined by a project arborist after considering the tree, the site and the proposed works. No output here establishes that a proposal complies, that a council will approve anything, that a tree can be removed, or that works are safe to proceed.
Palms, cycads and tree ferns are deliberately not calculated. AS 4970:2025 does not support applying the standard method to them, and inventing a substitute would be worse than declining to answer. A multi-stemmed tree is combined by cross-sectional area, which is one of two methods the Standard names — the project arborist chooses between them and gives their reasons.
Contact
Send Adam the address and he will take it from there
For many protected vegetation questions, the property address is enough to start checking. Call, or send the details below.