I am trying to make a floor plan for my office, have managed to make all of the rectangular components (e.g. the rooms) however some of the desk layouts are circular and I haven't been able to work out how to make exact and measured circles. They need to have a radius of 1.45m.
Take a look at the plug in CADDigitize. It may be helpful. edit : This tool allows the user to draw circles, squares, resctangels, ellipses from many ways.
According to this QGIS Change Log entry for the latest 2.10 "Pisa" release of QGIS, support for true curve features, including circles, was only just added in this latest release. See the "New geometry engine" topic. It requires a datasource like PostGIS that supports true curved geometry types.
However, the documentation there is slightly ambiguous. It suggests, that although QGIS based on the screenshot there will now read and display the curves, you may as of yet not be able to create or edit them through the QGIS user interface. See the phrase:
"In general you won't see many differences on the user interface yet, but this lays the foundation for a much richer set of geospatial capabilities that we will be able to support in the future."
Maybe someone who has the latest release installed, can answer the question whether creation and editing of true curves is already supported through the user interface with Pisa.