Circle in gmt

How to plot the circle of radius 250 km on a mercator projection map and lets say center is at 81 N and 27 east

Have a look at example 23 in the illustration gallery (all paths lead to Rome)
use grdmath to build a grid of the distance from the centre of your circle
use grdcontour to draw a single contour

gmt plot ktm.txt -W2,red, -SE-
This work for me. Ktm.txt is 3 column file with longitude latitude and radius(km). longitude and latitude is center of circle

And if fixed at 250km then just

echo 27E 81N | gmt plot -SE-250k -Gred

250 k is the diameter of the circle,isn’t it sir?

Please do not use me as a reader of the documentation. It is pretty clear if you look:

while on the command line -SE diameter will plot the degenerate ellipse

See also: