I have seen a similar question at Creating different diameter circles round points using QGIS but it is very old am seeking up-to-date and possibly more conclusive guidance.
I would like to create a new layer with circles of a specific diameter based on an attribute within a point layer. This relates to trees, specifically BS5837 In the UK.
For example with a DBH, (Diameter at Breast Height of tree stem), reading of 250mm I want to see a circle with a radius of 3m. This circle is typically calculated and then drawn manually in aCAD. I'm looking to improve this workflow.
The DBH/RPA calculation is simple.
RPA=DBH*12 normally I work this into meters for CAD (/1000).
Answer notes: The calculation Ive used in QGIS is slightly different to compensate for units (DBH*0.012) would work either way though. The projections were key in getting the correctly sized circles.
Many of the suggested methods, including those received here utilise buffer in Vector Tools this is likely the most robust solution however I have an issue that my projection (EPSG3857 - WGS84 Pseudo) is in degrees. In the answer provided below to arrive at a correctly formatted output I used EPSG:23030 - ED50 / UTM zone 30N.
My ultimate goal is to have some form of template style/formula/symbology/buffer that runs through the point data drawing all RPAs.
Answer notes: My next goal will be to condensed the newly learned workflow down into some form of template style or project i can import data into.
Many thanks to Håvard Tveite and others for input.