Do a couple speed tests. Try doing them at different times of the day to get a good average of your speed. At peak usage times your speed will probably be slower than at off peak times.
Speakeasy - Speed Test Speedtest.net - The Global Broadband Speed Test
Don't get confused between kilobits(kbs) and kilobytes(KBs), there are 8 bits to 1 Byte. So if the test shows results in kilobits, divide by 8 to get kilobytes. LW shows speeds in kilobytes:
SpeedGuide.net :: Bits/Bytes Calculator