The Screen Printing Calculator can be used to screen print better halftones. To print tone correctly, you must know your mesh count, be able to control the size of your halftone dot, and have a enough resolution in your image for the screen's mesh.
Pixels Per Inch (PPI) - Resolution of an image.
Lines Per Inch (LPI) - Number of lines of halftone dots per inch.
Threads Per Inch (TPI) - Frequency of threads in screen fabric.