The printing size of computer-processed images is calculated as follows:

Image height or width in pixels (e.g. 768 pixels)
Divided by the half-tone screen width (in cm) x 2.54 x QF (quality factor) (e.g. 54 x 2.54 x 2)
equals the Image height or width in inches (e.g. 768 / 274.32 = 2.79)
multiplyed by 2.54 equals the image height or width in cm (2.79 x 2.54 = 7.1)

Or:
Image height or width in pixels (e.g. 768)
divided by the half-tone screen width (in cm) x QF (e.g. 54 x 2 = 108)
equals the image height or width in cm (768 / 108 = 7.1)

The quality factor QF should usually be 2.
For half-tone screen widths over 133 lpi (approx. 54 lpcm) a QF of 1.5 may be sufficient (lpi = half-tone screen width in lpcm x ~2.54).

Calculation example using a video image - Pixel dimensions 768 x 576

For screen printing, the resolution of a video frame without interpolation is only sufficient for the above proportions. However, depending on the content of the image, the frame may be enlarged through interpolation.