How to know what lenses will fit a nikon d40?

Hi, I'm buying a nikon d40 and want to know if the lens I currently have will fit it. It is a tokina AT-X 270af PRO II. I currently have it on a nikon d1, and it says that it's made for nikons but since it's older I didn't know if the mounting had changed?

It should mount okay on the D40. However, I think this lens depends on the camera to have the autofocus motor which the D40 lacks. It will be manual focus only on the D40.

Nikon cameras still use the F mount first introduced in 1959. If your lens has an F mount, it should still be usable (but it could cause mechanical damage if it's more than 20 years old so check with the manufacturer). As far as I know, the D40 does not have a mechanical AF drive, so some autofocus lenses could lose this ability when used with it.

If that lens has a built-in auto-focus motor, it will work just fine with your D40

I looked for that lens on the Tokina website and could not find it.

There's a AT-X 280 AF f/2.8 which has an internal auto-focus motor so will work with your D40

http://www.tokinalens.com/products/tokina/afl-04.html

The only "270" I could find is a manual focus lens

Tokina at present make the best third party (generic) lenses for Nikon and Canon camera systems