Medium or standard size of my artworks - over 12 to 20 inches (~ 30-50 cm) longest side. 

These paintings and drawings can fit on most wall spaces and can be comfortably observed in standard size rooms and often require just standard size frames.

• Examples for the United States, in inches:
  
  • 15 x 11 inches - quarter imperial, 1.(36) aspect ratio;
  • 16 x 12 inches - a standard paper block size, 1.(3) or 3:4 aspect ratio;
  • 20 x 16 inches - a common US picture frame size, 1.25 or 4:5 aspect ratio.
• Examples for  Europe and Asia, in centimeters, all ~ 1.71 aspect ratio:
  • A3 standard - 30 x 42 cm, or 297 x 420 mm, 
    ~ 16.5 x 11.7 inches;
  • B3 standard - 35 x 50 cm, or 353 x 500 mm,
    ~ 19.7 x13.9 inches;
  • B4 standard - 25 x 35 cm, or 250 x 353 mm,
    ~ 13.9 x 9.8 inches.