Printing sizes = ppi pixel per inch

The American printing company zazzle recomends 200 ppi for post cards and 100 ppi + for posters
http://zazzle.custhelp.com/app/answers/detail/a_id/85#print
More is not bad. They just scale it down.
Those I printed in Finland were 80 x 60 centimeter =
60 cm = 23.6 in = 2360 pixels minimum
80 cm = 31.5 in = 3150 pixels minimum
http://manuelsweb.com/in_cm.htm
1 inch is 2,539682539 centimeters. Round up to 2,54 and you'l be fine.
0.3937008 in = 1 cm
My UF program is set to maximum  3200 x 2400 pixels which is roughly for a printing size of 80 x 60 centmiter by 100 ppi
But I can set UF to a higher value
3:14 min for the one layer simple fractal  101103dxMotherWorm 7 in to 3200x2400 pixel size. Rendering it 7:17 ( better for printing would take about twice that time )