The field of view is taken on the diagonal.
Published focal length for a lens will be the 35mm value, even if lens is made specifically for cameras using smaller sensors.

Full Frame (35mm)		Nikon DX		Canon Rebel		4 x 5"
35mm Equiv.   Field of View 10.0       130.38°     17.0       103.68°     18.0       100.48°     20.0       94.49°     24.0       84.06°     28.0       75.38°     30.0       71.59°     35.0       63.44°     45.0       51.35°     50.0       46.79°     55.0       42.94°     60.0       39.65°     70.0       34.35°     85.0       28.56°     90.0       27.03°     105.0       23.28°     135.0       18.21°     150.0       16.41°     180.0       13.71°     200.0       12.35°     300.0       8.25°     400.0       6.19°     500.0       4.95°     600.0       4.13°     800.0       3.10°     1000.0       2.48°		35mm Equiv.   Field of View 15.0       109.75°     25.5       79.80°     27.0       76.59°     30.0       70.80°     36.0       61.27°     42.0       53.83°     45.0       50.70°     52.5       44.21°     67.5       35.06°     75.0       31.74°     82.5       28.98°     90.0       26.66°     105.0       22.96°     127.5       18.99°     135.0       17.95°     157.5       15.42°     202.5       12.02°     225.0       10.83°     270.0       9.03°     300.0       8.13°     450.0       5.43°     600.0       4.07°     750.0       3.26°     900.0       2.71°     1200.0       2.04°     1500.0       1.63°		35mm Equiv.   Field of View 16.0       107.03°     27.2       76.99°     28.8       73.82°     32.0       68.12°     38.4       58.79°     44.8       51.55°     48.0       48.52°     56.0       42.24°     72.0       33.45°     80.0       30.26°     88.0       27.62°     96.0       25.40°     112.0       21.86°     136.0       18.08°     144.0       17.09°     168.0       14.68°     216.0       11.44°     240.0       10.30°     288.0       8.59°     320.0       7.74°     480.0       5.16°     640.0       3.87°     800.0       3.10°     960.0       2.58°     1280.0       1.94°     1600.0       1.55°		35mm Equiv.   Field of View 3.0       165.98°     5.1       156.38°     5.4       155.04°     6.0       152.37°     7.2       147.11°     8.4       142.00°     9.0       139.50°     10.5       133.43°     13.5       122.08°     14.9       116.83°     16.4       111.86°     17.9       107.16°     20.9       98.56°     25.4       87.46°     26.9       84.20°     31.4       75.51°     40.4       62.13°     44.8       56.93°     53.8       48.62°     59.8       44.25°     89.7       30.33°     119.6       22.98°     149.5       18.48°     179.4       15.44°     239.2       11.61°     299.0       9.30°

35mm Full Frame: Film cameras; Nikon D3; Canon EOS 1Ds Mark II, Canon 5D
Nikon DX: Other Nikon DSLR; Minolta Dynax 7D; Fujifilm FinePixS3 Pro; Pentax 1s DS
Canon Rebel: Other Canon DSLR

Values are calculated based on exact focal lengths and may vary slightly from those published for a given lenses.
Note that lenses used in Macro/Micro mode and Fisheye lenses will differ from these values.