Calculate photo dimensions

Proportions: fix the target width, height or long edge and round the other axis. Pixels and physical size: convert both ways using mm/cm/in and PPI. Placement: contain reports margins; cover reports cropping and placement PPI. Placement analysis does not crop a photo or create a print canvas.

Physical mm = pixels ÷ PPI × 25.4. Required pixels = ceil(mm ÷ 25.4 × PPI). 3,000×2,000px at 300PPI is 254×169.333333…mm. Full A4, 210×297mm at 300PPI, requires 2,481×3,508px when rounded up. Rounded presets may differ by 1px; this is not the printer’s printable area.

4,000×3,000px at a target width of 1,600 gives 1,600×1,200px. In a 200×200mm rectangle, contain places it at 200×150mm, 508PPI, with a 25mm vertical margin per side. Cover places it at 266.667×200mm, 381PPI, with 33.333mm horizontal cropping per side.

Changing a PPI number does not add detail or write a PPI tag to a file. 150/300PPI are comparison values, not universal pass marks for every printer or photo. Enlarging a small photo cannot create new detail.

Calculation inputs: integer pixels 1–1,000,000, integer PPI 1–1,200, physical lengths up to 10,000mm and six decimal places. Large calculation results are separate from the editor’s 8,192px/12MP/32MP total/10-photo limits. The editor does not upscale and does not offer HEIC/AVIF, automatic printing or tiled PDFs.

Choose a photo in the editor and explicitly load its current values in the size helper. It uses effective dimensions after EXIF normalization, cropping, rotation and straightening. Only proportional pixel sizes can be applied explicitly. Calculating or closing the helper preserves photos and review states.

JPEG/WebP targets use actual file bytes and cannot guarantee success. My output settings stores recipes; each new photo must be calculated again. Make a cover from the current reviewed photo. The 4:3/1:1/16:9 ratios are product suggestions, not official platform specifications. Cover sensitive details and review the actual result before saving.