For clarity sake, we will base all these calculations off a hypothetical $400,000 home.  This will give you an idea, based on the results, of how you can quickly calculate the tax rate in the future.

CHATHAM COUNTY

The following calculations are going to be based of the table found in this link
For example, if you buy a property in Savannah, you will pay $44.313 per $1,000 of assessed value.  So, for example, if the home is $400,000 then the taxable portion is 40% of that… or $160,000.  Then the annual tax liability will be $7,090.  You would just use the first table on that page to do your calculation.

For another example, if you buy a property in the unincorporated county, you will pay $36.375 per $1,000 of assessed value.  Using the same purchase price and 40% rule, the tax liability of that home will be $5,820.  You would use the second table on that page.

For the last example, if you buy a property in Pooler, you will pay $40.026 per $1,000 of assessed value.  Using the same purchase price and 40% rule, the tax liability of that home would be $6,404.  In this case, you would add the municipal tax rate (found near the bottom of the page) for that city to the total county tax rate. There are a few other municipalities in the county, so choose accordingly.

*outside Savannah, there is a fire service fee from Chatham Emergency Services which will vary from $275 to $500 (depending on size)*

BRYAN COUNTY

They make it easy, just use this link.
If it’s part of one of the two city districts then select it from the dropdown, and if it’s in the unincorporated county then leave it there.  I can help you with that if you give me an address.  You will not use the Exempt (0) selection.  If this would be your primary residence, you’ll click the button for Homestead Exemption “Exempt”.  If not, then leave it there.  Then, just type in the purchase price $400,000.

This house in Richmond Hill (city boundary) would have a tax liability of about $4,314.  There is an additional $185 fire fee for residents.
The same house in the unincorporated county would have a tax liability of $3,662. In the county, you’d add a $220 fire and $180 trash.

EFFINGHAM COUNTY

They also make it easy, just use this link.

 
If it’s part of one of the three city districts, select it from the dropdown.  If it’s in the county, leave it there.  Again, I can help you with that if you give me an address.  If this would be your primary residence, you’ll click the button for Homestead Exemption “Exempt”.  If not, then leave it there.  Then, just type in the purchase price $400,000.  

You’ll see that a Guyton resident would pay about $4,840.
For the same price home, a Rincon resident would pay $4,226.
In Effingham County, emergency services are part of your property tax bill, so there are no extra charges.