Pixels to cm

[randomer]

I am using Macromedia Fireworks 8 and have a problem with the size of my images that I am creating. I want the eventual print size to be 8.5 cm x 7.5 cm. I type this in and go to 100%. Sometimes it works but other times the size is incorrect. It seems that the 'pixels/cm' attribute is causing this. Could anyone tell me what the average normal size is for this so that my print size will be correct without looking grainy.
Thanks.

[rojash]

Weh submitting images for print it is normal to specify 300 dpi, whereas for screen it is usually 72 or 96 dpi. (I'm sure you can convert this to from inches to cm yourself (in fact, I'm prettyr sure that Fireworks will allow you to specify in DPI)

[randomer]

Cheers. You have saved my coursework.