Add bleed to both sides
Bleed is artwork extending beyond the intended trim edge. With the same bleed on all four sides, add twice that amount to the width and twice to the height. A 100 × 150 mm trim with a hypothetical 3 mm bleed per edge needs a 106 × 156 mm artwork area.
That example is arithmetic, not a printing standard. Some products require a different bleed, different amounts per edge, or none at all. Use the template and instructions for the exact product you are ordering.
Bleed is not a safe margin
Background colors or images intended to reach the finished edge should extend into the bleed. Important text and faces usually need a separate safe area inside the trim. Enter a safe inset to preview that inner area. The calculator illustrates your settings; it does not decide the required safety margin or create a production PDF.
Pixel estimates convert the full artwork size to inches, multiply by the chosen PPI, and round to the nearest whole pixel. The extra canvas still needs real artwork. Adding blank space or merely changing a density label does not extend a photograph’s content.