I need to know the maths for pixels + DPI to mm. For kitely.

mm2px.py

"""
python mm2px.py 290 210 150
"""
import sys
w = float(sys.argv[1])  # 1830
h = float(sys.argv[2])  # 1547
dpi = int(sys.argv[3])  # 150
w_mm = (w * dpi) / 25.4
h_mm = (h * dpi) / 25.4
print((w_mm, h_mm))

px2mm.py

"""
python px2mm.py 1753 1240 150
"""
import sys
w = float(sys.argv[1])  # 1830
h = float(sys.argv[2])  # 1547
dpi = int(sys.argv[3])  # 150
w_mm = (w * 25.4) / dpi
h_mm = (h * 25.4) / dpi
print((w_mm, h_mm))