What kind of zoom will you get on 300mm lens on crop sensor?

I have 75-300mm lens. What kind of magnification will i get on crop sensor. This is a canon lens, so assuming a canon crop sensor on canon camera. I was told it would be 480mm. But what i'm interested in is in times. Like i have nikon binoculars with zoom from 8 times to 24 times. It is really good zoom on binoculars. Also have 12 times zoom on panasonic cam corder.these are good zooms.
I want to know what kind of zoom will 480mm lens will equate to in those specs like on binocular and cam corder. Sony bridge cameras also have zoom in times.
Second question is, if i get a spacer for that lens, 70-300mm, what kind of zoom then will it be? Will a picture still be usable with a spaces, because there would be less light i presume.

You have 4.28 x zoom (70 mm to 300 mm)

A 50 - 500 mm lens is 10 x.
A 16-35 mm lens is 2.18 x

The spacer as you call it will allow your lens to focus closer, but it won't work well with that lens. And furthermore, you won't be able to focus to infinity.

I use an old 35mm film lens that zooms 100-300 on my 30d its fantastic, about like a 15x or so zoom on canon and nikon crop sensors

Your kit zoom is probably 18 to 55mm. Looking at the 18mm and the 300mm, you can say that mathematically 300mm is 16x. But compared with 55mm, 300mm is about 5.5x. The 'standard' lens for crop frame is considered to be 30mm, thus 300m is exactly 10x. So it all depends where yiou start from. Most 'bridge cameras' these days start from a full-frame equivalent of 28mm (18mm on crop frame), so their 16x would approximately equal your 300mm on your crop frame. Strictly speaking 300mm on full-frame is equivalent to 450mm on crop frames generally, but a little longer on Canons.

The bottom right hand corner shows you how it will look:

The "X" doesn't really matter, because it's "X What?" A 75-300 is a 4X zoom, but since the normal for your camera would be about 35mm, the 300 end is 8.5X from the normal view or almost 16X from the wide 18mm end of the kit zoom.

If the crop factor is 1.6x then multiply the focal length by 1.6

300mm x 1.6 = 480mm equivalent

300mm/70mm = 4.28x zoom

The x(times) zoom figure tells you nothing about the true zoom of a lens - all it tells you is the zoom factor between the shortest focal length and the longest. It doesn't tell you how close you can get.

for example a 10-24mm is 2.4x zoom - but it's not a telephoto lens - everything will look further away than what you normally see with your eyes - because it's a wide angle zoom - in real terms it has a minus zoom if you like.

Don't know what you mean by a "spacer" - are you talking about an extension tube? - that's for macro work. Or if you mean a converter, then it increases the zoom by the factor written on the converter.

Cropped sensor multiplying factor gives you the times your lens be equivalent to: 1.4, 1.5… Depending on size; telelens amplification is not measured in times (macro lenses do), but in focal length or angle view
A spacer between body and lens gives you a macro view