Comparing camera lens when they have different size sensors

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I wanted to compare pictures and found my compact does not give the dimensions of the sensor in the normal mm x mm format but in square inches. My D-SLR's both have different sensor sizes which made comparing rather a problem. So I sat down and wrote a program to convert into 35mm film format.
Camera Lens Calculator
However when I put the info for my Tamron lens into the calculator I found it was a few minutes out. Tamron 18-270 mm used on a Nikon says angle of View = 75º 33' - 5º 51' with a 15.5 x 23.2 mm sensor.
So is it:-
1) I got calculation wrong.
2) The lens is a 18 - 273 mm.
3) Something else.
The Casio EX-Z600 instruction manual said it had a 1/2.5 inch sensor which however I tried seemed to give daft results. However when I tried 1/25 of inch everything dropped into place.

OK I know no real point I was just playing. I would guess the angle of view is the more accurate as the focal length depends on the sensor size.

I have found the Fugi says “1/2.3 – in., square-pixel CCD with primary color filter” and again I can't work out what it refers to? I have modified calculator so I can go round in a circular fashion and all the D-SLR details seem to tally with results I am getting but there seems no way I can relate the readings to the 1/2.3 and 1/2.5 given in the Fugi and Casio compact cameras.