RF Planning Tools
Radio Mobile Online 
Create an account
Set up a New Site by finding it geographically on the map and placing the flag, then click Submit. Make sure to give the New Site a name when prompted, otherwise it gets confusing later on.
One you have the site saved, go to New Coverage and in the drop down menu select the name of the Site you want to do the coverage map for.
Fill in the information pertaining to the power and antenna you will be using. For Mobile Antenna Height, put 1.5 meters which is the average height someone will be holding their cell phone at when talking. Mobile Antenna Gain should be between 0 and 2 dBi. For the Frequency put 902 (if you are doing 850mHz or 900mHz celular), which is in the ISM band, otherwise it won't let you Submit at the end. Set Rx threshold to 0.709, which is -110dB (noise floor for GSM) and Required Reliability to 99%. It is important to calculate your line loss, especially on the Tx side, which you can do here 
Once all the parameters are in, press Submit. It will calculate for a while then will show you coverage map, based on what you entered as the parameters.