This is my  short list of preferred web calculators that i use frequently to make fast RF and simple on line circuit simulations:

http://www.changpuak.ch
http://coil32.net/online-calculators.html
http://www.claredot.net
http://tonnesoftware.com/index.html
http://www.daycounter.com/Calculators/

We can make a comparison between the calculators, to be sure of schematic RF values results, but littles differences are normal and  will be corrected during pratical construction. You must consider almost a 5 % of tollerance in RF value and, above all, use only a right selection of electronic components.