Working on a road junction I would like to make a perfect rounded circle buffer of 1 km around this junction in QGIS 3.4. Here is what is look like now.
If you start a new editing session you can create a new polygon circle that estimates the size of the buffer.
You can make it more exact by referencing the coordinate points at the far points of the buffer.
You won't be able to make a circle that is exactly the same distance from every extremity of the road because it is an uneven shape.