F-18C TWR with 5 minutes of [afterburning] fuel [54.4% aka 2550kg], 10433kg airframe, ~150kg of man and oil, and 8 missiles [1056kg]. 14189kg.
18,000kgf / 14189kg = 1.268:1 TWR.
Meanwhile F-18E with 5 minutes of fuel [3084kg] + 14552kg airframe, ~250kg of man and oil, and 8 missiles [1056kg].
20,000 / 18942 = 1.056 TWR.
Source?
The math is right there in the post.
As for the math for getting 5 minutes of fuel:
22,000 x2 is 44,000, x1.85 TSFC gets pounds per hour. /2.2 for kg, /60 for hours to minutes. x5 for 5 minutes of fuel in kg, for F-18E.
((22,000x2x1.85) / 2.2 / 60) x5
Weapons data is from WT.
And empty masses are claimed masses by the manufacturer.