Photo dimensions: pixels, centimetres and DPI

Start with four separate requirements

Before editing, identify the frame ratio, physical size if relevant, pixel dimensions and maximum file size. A 3:4 ratio describes shape. A 3×4 cm measurement describes physical size. A 354×472-pixel file describes the raster dimensions. A 200 KB cap describes the data budget.

Not every destination needs all four. Online forms commonly specify pixels and bytes; print tasks need physical dimensions and suitable density. Follow the actual instructions rather than inferring a requirement from an ambiguous filename.

Convert centimetres to pixels

The calculation is pixels = centimetres ÷ 2.54 × DPI. For inches, multiply inches by DPI. The output must use whole pixels, so Toolmova rounds the calculation. Small rounding differences are normal when physical sizes become a raster image.

Understand what DPI can and cannot do

DPI links a pixel count to a physical print size. Raising a DPI value alone does not recover a missing face detail or sharpen a blurry source. If you request more pixels than the original contains, resizing interpolates existing information.

Toolmova uses the chosen DPI to calculate pixels and writes the density into JPG metadata for resize and centimetre-preset outputs. The browser's default canvas export alone normally uses 96 DPI metadata; this build explicitly replaces that density. Your print program may still ignore it or apply its own scaling.

3×4 and 4×6 need an explicit unit

The 3×4 preset and 4×6 preset here use centimetres. A 4×6 inch print is much larger than a 4×6 cm photo, despite having the same 2:3 shape. Use the custom resizer with inches when that is the intended unit.

Avoid assuming that a common photo label defines an official specification. An organisation may ask for a particular pixel size, background or framing that differs from a generic centimetre preset.

Crop a different ratio; do not squeeze it

If a wide landscape image must become a portrait, something has to give. Stretching it changes the shapes of subjects. Cropping preserves their proportions while removing material outside the selected rectangle.

Move the frame in Crop photo or the locked photo presets to decide what remains visible. Check the crop before exporting. The tool does not recognise a face, generate a background or validate a document photo.

Check file size after geometry is correct

Once the frame and pixel dimensions are correct, apply a byte cap only if required. Compression changes the encoding quality within those dimensions. Resize and preset tools do not silently shrink your specified output to meet the cap.

If a required pixel output cannot fit within the requested bytes at the available quality settings, increase the cap or reconsider the allowed dimensions with the destination's rules in mind. See the file-size guide for exact units and a final checklist.

Before printing

• Set the intended centimetre or inch size and a suitable density for your task.
• Inspect the output at a useful zoom level, especially when enlarging.
• Turn off unwanted fit-to-page or borderless scaling in the print application.
• Check the printed result with a ruler when physical dimensions matter.
• Confirm any document-specific background, expression and framing requirements separately.