How to use
Choose Pixels → print size when you already know the image’s pixel dimensions. Width and height are then whole pixels, while the unit selector controls the physical output. Choose Print size → pixels when planning a physical print; width and height then use the selected cm, mm or in unit. Set your target image resolution in pixels per inch (PPI) and calculate.
The mode changes what the width and height numbers mean; it does not convert existing entries for you. Replace them with values appropriate to the new mode before calculating. The optional source dimensions let you compare an existing image’s ratio with the intended print. Enter both or leave both empty.
The pale examples calculate without editing. Focusing any numeric field clears all examples together; later edits keep your own values. The compact diagram stays visible when values are missing or invalid. Dimension labels update with valid values; a dash means the dimension is not yet available.
Method and units
Print inches = pixels / PPI. Required pixels = print inches × PPI. Centimeters convert to inches by dividing by 2.54; millimeters by 25.4. In the reverse direction multiply inches by those factors. One centimeter is ten millimeters. Width and height are calculated independently.
Required pixel counts are rounded up separately, because rounding down would fall short of the requested size at the target PPI. The print diagram keeps the requested physical proportion and shows quarter-interval dimension marks. It is a scaled drawing, not an actual-size paper preview.
Two examples
A 3600 × 2400 pixel image at 300 PPI covers 12 × 8 inches, or 30.48 × 20.32 cm. Selecting millimeters instead gives 304.8 × 203.2 mm. The image remains 3:2.
A 10 × 15 cm print at 300 PPI needs at least 1182 × 1772 pixels after upward rounding. The physical ratio is 2:3. A source of 3000 × 2000 has a different orientation and ratio, so the optional check reports a mismatch.
Limits and practical use
Use positive values up to one billion, with a decimal point or comma and no thousands separators. Pixel inputs must be whole numbers. Results above one trillion are rejected. Measurements normally show at most two decimal places; tiny positive values are marked as less than 0.01. Pixel counts remain integers.
Copy result includes print dimensions, pixels, ratio and any source-ratio warning. Edits and mode changes invalidate the confirmed result until you calculate again. Clear empties the inputs and keeps the empty diagram while preserving mode and unit selections.
Is image PPI the same as printer DPI?
No. PPI describes image pixels per printed inch; DPI describes printer ink dots. Do not substitute an ink-dot specification for the desired image resolution.
Does a target PPI guarantee quality?
No. Source detail, compression, paper, printer and viewing distance matter. This calculator does not improve or upscale the image.
What happens when ratios differ?
The warning identifies a mismatch without stretching or cropping. Rotate, crop, add margins or change the requested dimensions in a separate editing step.
Are rounded pixels an exact ratio match?
Not always. Independent upward rounding can slightly change the integer pixel ratio. The physical print ratio remains visible so you can make the final production decision.