coverage calculation

[josephium]

can anyone answer me plz

first case:if i have an access point with 100mw of power and i install to it an omni 18dbi antenna then what would be the maximum coverage of that antenna in an outdoor environment,would it be a 500 meter radius for example?

second case: i have 2 sites i want to link together wirelessly,if i got 2 bridges(100mw) and 2 yagi 18 dbi antennas for example to link the 2 sites, these antennas will have what range if i have good RF LOS? how do i calculate it?
if the sites for example are 800 meters away how do i calculate if i need 2 12 dbi yagis or 2 18 dbi yagis...?

thanks in advance

[josephium]

sorry i guess there is no 18dbi omni antenna, my fault.

so there is way to calculate it? i have downloaded the cisco bridge outdoor range calculator and it gives u the range when u input what type of antenna and power you are using it .xls and its good but i wanted to know how do they calculate it.

thx