Root Protection Area Calculator Tool

Welcome to our BS5837:2012 Root Protection Area (RPA) Calculator.

A valuable tool designed to facilitate architects, landowners, developers, and consultants in understanding the potential rooting area of trees on their land. 

This is a design tool - please consult an arboricultural expert to assess soil conditions, local structures, site levels, species, tree age and confirmed RPA calculations - all of which impact the use of Root Protection Areas. 

Using the Calculator

  1. Measure the tree - method below

  2. Enter measurements into the calculator

  3. Use the RPA Radius to understand site constraints

Single Stem Tree Image with an indication to measure at 1.5 metres

Measure the diameter of the tree at 1.5m

Single Stem

Multi stem image which an indication to measure at 1.5 metres off the ground for each stem

Measure the diameter of each stem at 1.5m

Multi-stem

A tree with the Root Protection Area radius marked in a circle on the ground around the tree

The calculation output is the distance from the stem to the edge of the Root Protection Area

RPA Radius

Single-stem tree calculator

Please enter a valid diameter (1-1000cm)
Maximum RPA radius is 15 meters
BS5837:2012 RPA Radius:
For guidance only

Multi-stem trees calculator

For single stem trees, please use the single stem calculator
BS5837:2012 RPA Radius:
For guidance only

Details and help

This calculator helps you gain valuable insights into the spatial extent of tree roots, enabling informed decision-making and planning.

Whether you're navigating construction projects, landscaping endeavours, or property development, our BS5837:2012 RPA Calculator helps provide estimates that can inform your early design decisions.

A copy of the British Standard 5837:2012 is (currently) available for FREE here.

All Silva take no responsibility for any issues arising from inaccuracies produced in conjunction with this tool.

  • If the stem circumference has been measured using a standard tape measure, the figure will need to be divided by π (3.14159) to get stem diameter. 

  • The calculated output is capped at 15m radius, however this may be extended if the tree is ancient or veteran.

  • RPA Radius (in metres) = 0.12 × stem diameter (in cm)

  • Combined Diameter = √(stem1² + stem2² + ... + stem5²)

    RPA Radius (in m)= 0.12 x Combined Diameter (in cm)

  • Combined diameter = √((mean stem diameter)² × number of stems)

    RPA Radius (in m) = 0.12 × Combined Diameter (in cm)cription

This is a design tool, and should be used in conjunction with arboricultural expertise to assess ground conditions, biomechanics, tree root morphology, species etc.