When printing edited digital photos, how do I determine the pixel dimensions so that it fits perfectly on 8X10

I recently purchased a digital SLR camera and have ran into a problem printing photos on my dell 942 photo printer. I'm trying to figure out some mathematical formula so that when I crop the photos to get the image area I want, I can get them to fit perfectly within the borders of whatever size I'm printing(such as 8X10, 5X7, envelopes, etc.), but I can't find anything on the net. I've tried calculating it myself but there's always one dimension that winds up with a small bit of border, unless I choose the "borderless" option when printing, but that distorts the original image by stretching it to fit. Does anyone know of a good way to deal with this problem?

Barkley answered that you "crop the picture so that the ratio of pixels is the same as the size ratio. You then have to set the print size to match that area". I hope I don't sound like a complete idiot, but I don't quite understand this. For example, I am looking at a jpg that measures 558X461x16.1 million pixels. I know that 558 would be the longest dimension, but I could crop some of the image without destroying the integrity of the scene. if I were to use a full 8.5X11 inch sheet of photo paper and I wanted to print this image to fill the entire sheet, what dimensions would I crop the image to, or, what formula do I use to calculate the ratio?

First you have to determine the exact print area on your 8x10 paper. Let's say that it is 7.75 x 9.5. Now crop the picture so that the ratio of pixels is the same as the size ratio. You then have to set the print size to match that area. I would not let the printer default to filling print area. Set the exact size in the photo editing program and tell the printer to print actual size.

Remember that number of pixels and print size are independent. The more pixels the clearer the picture but not necessarily a larger picture.

ok well theres your one problem dell's suck try adobe it should let you do what you want