Extension Tubes for zoom Nikon lenses?

I have a Nikon d90 with a 18-105mm and 55-300mm lenses. Also have Zeikos extensions tubes: 12mm, 20mm, 36mm. I would like to know what combinations can I use with my lenses to get a real macro photo (1:1). Ex: 18-105 and 12mm and or 36mm; 55-300 and or 20mm, 12mm, 36mm etc.etc. I know the quality of the macro will never be the same as using a real macro lens, but now I don't have $$$$$ to get the macro.

Technically, an object 2 focal lengths in front of the lens will appear life size 2 focal lengths behind it.(18mm/36mm extension tube, 36mm lens-to-subject).

Or you could just try various combinations to get the effect you want.

If I remember correctly, extension length divided by focal length = magnification (or close enough for government work).

There are several caveats to that… The lens in use may not be able to focus the image with extension tubes, more of a problem with longer or stacked tubes. If your tubes are not built to allow the camera body to control aperture on those G lenses, you won't be able to see anything anyway. And you do lose a little light, again the more extension the more you lose. With a 20mm, the loss will be so slight as to not really matter.

Your 18-105 with a 20mm tube, lens set at 18-20mm, will give you 1:1 or so shots. If you can get focus. Using the 36mm should get you 2:1. Stack them all together and you can get about 4:1, but the odds of this combo working are pretty slim.

Get an old Nikkor 28 or 35mm manual lens to use with your tubes. Much easier and better quality.