Tree Protection Zone Calculator

This calculator can define and insert a symbol to represent protection zones relative to a tree’s measured stem and buttress dimensions.

The tool is based on an Australian Standard (AS 4970-2025) with calculation formulas the same as those for the earlier AS 4970-2009 but with some new terminology including the The Notional Root Zone (NRZ) representing the theoretical area necessary for a tree’s health and long-term viability.

The tool can be started from the command line by typing ‘tpz’ or clicking the TPZ Calc button from the main dialog.

All symbols inserted into the drawing can be edited by changing settings from the dialog, including linetype scale, layer and colours.

Single and multi stem tree dimensions can be calculated. Each symbol is uniquely named with a common prefix and can be modified if needed via the block editor.