ImgExact

DPI converter and print size calculator

Mark an image for a target print resolution (for example 300 DPI) or calculate what physical size your pixels support. No fake "detail upgrade" claims.

Images never leave your device No signup, no email No file limits or watermarks Works offline once loaded

What do you need?

Last reviewed . Runs locally — your images never leave your device.

How it works

  1. Drop your image and read its pixel dimensions.
  2. Option A — Print size: enter a DPI and see the physical print size in inches/cm.
  3. Option B — Set DPI: write a density value into the file the way print workflows expect.
  4. For required print sizes, the calculator tells you how many pixels you actually need.

Common requirements

  • 300 DPI — The standard print density for photos, flyers and photo books.
  • 150 DPI — Large-format prints viewed from a distance, such as posters.
  • 72 DPI — A legacy web convention — harmless, but meaningless to browsers.
  • 600 DPI — Detail-critical print when the pixels are actually available.
  • Print size from pixels — pixels ÷ DPI = inches; the calculator does it in both directions.
  • Pixels needed for a print — inches × DPI = pixels — check before cropping or shooting again.

What 300 DPI means and how to set it on an image

A print shop asking for "a 300 DPI file" is asking for a density instruction, not for more detail. The 300 DPI converter on this page writes that instruction into the file the way print workflows expect — a JFIF density field for JPEG, a pHYs chunk for PNG — without resampling a single pixel.

The arithmetic does not change: what matters is how many pixels cover the printed area. The print size calculator converts pixels to inches at any density (3000 px at 300 DPI = 10 inches) and works backwards from a required size (12 inches at 300 DPI = 3600 px).

So there are exactly two honest ways to change dpi of image: mark the intended density (this tool), or supply more real pixels (resize, or rescan). Software that promises a sharp 300 DPI print from a low-resolution photo is resampling and calling the interpolation an upgrade.

For screens, DPI is irrelevant — browsers lay out by pixels. It matters for print, for some PDF workflows, and for portals that inspect the density field before accepting an upload.

Supported formats

JPEG (JFIF density embedding) and PNG (pHYs chunk embedding); all formats for the calculator.

Metadata marking does not alter pixels — see the explanation below.

Privacy

Everything happens in your browser: the image is decoded, transformed and encoded locally. Nothing is uploaded, and no filename, pixel data or metadata is sent anywhere. Read more on the privacy page.

Technical methodology

  • JPEG output: a JFIF APP0 density field (units = dots per inch) is applied to a re-encoded copy. PNG output: a pHYs chunk (pixels per meter) is written with a matching value.
  • The pixels themselves are not resampled — DPI metadata tells print software how large to reproduce the image; it cannot add detail.
  • The calculator uses the standard formula: print size (inches) = pixels ÷ DPI.

Known limitations

  • If the file must stay byte-identical apart from metadata, note that PNG/JPEG embedding re-encodes pixels (quality is kept high).
  • Some apps ignore density metadata entirely and use raw pixels — that is app behavior, not a tool failure.
  • Bitmap formats outside JPEG/PNG do not get a density field from this tool.

Go deeper: image size vs dimensions vs DPI

Image size checker Instant report: file size, pixels, ratio, megapixels, metadata, print size. Metadata viewer & remover See EXIF, GPS and software tags locally — then remove them with verification.

Frequently asked questions

Will changing DPI make my image print sharper?

No — and any tool that claims otherwise is misleading you. DPI is a print instruction. Sharpness comes from pixels: a 600x600 image prints sharp at 2x2 inches at 300 DPI, and nothing can add detail beyond the pixels you have.

My print shop asked for a 300 DPI file. What do I do?

Two steps: (1) check the required print size in inches, (2) use the calculator to see the pixel count needed (inches × 300). If your image has fewer pixels, it will be interpolated by the printer — use this tool to mark 300 DPI and note the real resolution honestly.

What is the difference between DPI and PPI?

Technically, images have PPI (pixels per inch) and printers have DPI (dots per inch). In everyday usage they are interchangeable — "300 DPI photo" means 300 PPI. This tool marks the standard density field understood by print workflows.

How do I convert an image to 300 DPI without losing quality?

If the file already has enough pixels for the print size, marking the density changes no pixel data at all — that is the clean path. If it does not have enough pixels, nothing can add real detail; the calculator tells you how many pixels the size would require, and resampling is at best a cosmetic fix.