DPI Calculator

Calculate print size or PPI and inspect supported JPEG/PNG density tags locally.

Calculate print size from pixels and PPI, or effective PPI at a chosen print size. “DPI calculator” is a common name; image PPI and printer ink-dot DPI are different measurements.

Optional: inspect a JPEG or PNG

Choose an image to inspect

JPEG or still PNG, up to 10 MiB. Reads header dimensions and supported density tags; no image is displayed, resized or rewritten.

Pixel width

Pixel height

Calculation mode

Physical measurement unit

Calculation PPI

300 is an editable example, not a value inferred from your file or a quality guarantee.

This tool runs entirely in your browser. Your data is never uploaded, never stored, and never leaves your device.

Calculates image print size or effective PPI from pixel dimensions, with optional local JPEG/PNG density and orientation inspection.

How to use it

1Enter pixel dimensions or inspect a supported JPEG/PNG.
2Choose print size at a PPI, or effective PPI at a physical size.
3Review the dimensions and warnings; download a separate numeric report if needed.

Example

Input: 3000 × 2400 pixels at 300 PPI
Output: 10 × 8 inches · 254 × 203.2 mm

No resampling or metadata rewrite occurs, and the result is not a print-quality guarantee.

What happens to your data

Image inspection stays in the local worker. Reports contain supported dimensions/density/orientation, excluding image bytes, source filenames and unrelated camera/GPS fields.

Last updated October 2026

Work out how large an image can print at an entered pixels-per-inch value, or calculate effective PPI at the print dimensions you want. Enter pixel width and height manually, or read them from a local JPEG or still PNG. Optional density inspection shows supported embedded tags without treating their numbers as proof of image quality.

People often call this a DPI calculator, but image PPI and printer DPI are different quantities. PPI measures image pixels per printed inch; printer DPI measures dots of ink or toner. Changing a number in a calculation cannot add image detail, sharpen a blurry photograph or certify a print result.

How it works

In Print size at a chosen PPI mode, enter pixel width, pixel height and the PPI you intend to use. Physical width in inches equals pixel width divided by PPI, and the same applies to height. At 300 PPI, 3000 × 2400 pixels corresponds to 10 × 8 inches, or 254 × 203.2 mm. The initial 300 setting is an editable example, not a density inferred from a file and not a universal quality recommendation.

In Effective PPI mode, enter the desired physical width. Keep pixel aspect ratio derives height without stretching. Disable that option to enter both physical dimensions; the tool then reports horizontal and vertical PPI separately and warns if those proportions differ from the image. A printer’s actual fit, fill, crop, borderless and scaling settings can change the outcome. This calculator does not simulate those settings or decide which crop should be used.

Pixel dimensions must be whole numbers from 1 to 1,000,000 per edge. Entered PPI must be positive and at most 10,000. Physical input dimensions must be positive and at most 100,000 selected units; exceptionally large calculated sizes or PPI values are rejected. Results use ordinary floating-point arithmetic and are rounded for display; JSON and CSV retain the calculated numeric values. Switching inches, millimetres and centimetres converts the current physical input dimensions so their intended size does not change.

Optional image inspection accepts supported JPEG and still PNG files up to 10 MiB. A bounded local worker reads structural headers and supported density metadata; it does not render or decompress the image pixels. A recognized header is not a complete test that every raster pixel is decodable. Animated PNG, MPO, JUMBF compound images and other unsupported structures are rejected by the shared structural reader. WebP, TIFF, HEIC, SVG and RAW are outside this tool’s input scope. Use the appropriate converter first if suitable.

For PNG, a pHYs value with metre units converts to PPI by multiplying pixels per metre by 0.0254. Unit zero describes aspect ratio only, not physical density. For JPEG JFIF, unit 1 is pixels per inch, unit 2 is pixels per centimetre and unit zero is aspect ratio only. EXIF inspection reads main-image IFD0 XResolution, YResolution and an explicitly present ResolutionUnit. Thumbnail and focal-plane resolution are not substituted. This checker deliberately does not infer a missing EXIF unit tag or manufacture a missing X/Y resolution value. The supported tag coverage is partial; XMP density is not interpreted and its presence is flagged where detected.

Every supported density source is shown separately. Disagreement beyond 0.1 PPI or 0.1 percent of the first reported axis value is flagged; small integer/rounding differences can therefore agree within that tolerance. No source automatically replaces the calculation PPI. A missing physical-density tag does not mean an image is unsuitable for printing, and an embedded 300 value does not mean its pixels contain enough detail for any chosen print size.

EXIF orientation 5–8 swaps the displayed pixel axes. The calculator fills manual pixel fields with those display dimensions, while preserving stored dimensions and stored-axis density values in the report. Mirroring has no effect on the dimensions. If EXIF cannot be interpreted consistently, orientation is treated as unknown, stored axes are used and a warning explains the limitation. Editing either pixel field switches back to manual dimensions and clears the previous image report.

Changing inputs invalidates the old calculation. Choosing another image, Clear or Cancel prevents late worker results from replacing newer work. Workers stop after 10 seconds after startup; a timeout produces no completed inspection. The source image and metadata are never rewritten. JSON/CSV downloads contain the calculation, dimensions, orientation and supported density information, excluding image bytes, original filename and unrelated camera/GPS metadata. Review reports before sharing; local processing is not a claim that every surrounding website network request is absent.

Worked example: Calculate a print size without changing pixels

Input: Pixel width: 3000 Pixel height: 2400 Calculation PPI: 300
Result: 10 × 8 inches 254 × 203.2 mm 300 × 300 effective PPI

No image is resized or rewritten. Print quality still depends on source detail and the printing workflow.

Common use cases

Checking the physical size available from a known pixel count
Estimating effective PPI for a poster or photo layout
Distinguishing missing density tags from insufficient image dimensions
Comparing conflicting JFIF, PNG or supported EXIF density information

Frequently asked questions

Does changing DPI here make an image sharper?＋

No. This calculator changes neither pixels nor metadata. Entering a higher PPI yields a smaller physical print size for the same pixel count; it does not create detail.

What is the difference between DPI and PPI?＋

PPI counts image pixels per printed inch. Printer DPI counts output dots, such as ink or toner dots. They are related to a printing workflow but are not interchangeable measurements.

Why does my image show no embedded PPI?＋

Supported density tags may be absent, unitless, incomplete or outside this checker’s coverage. Enter the PPI or physical print size you intend to use. The tool does not assume 72 or 96 PPI.

Which density tag should I trust if values disagree?＋

The checker shows each supported source and warns about disagreement. It does not choose one automatically; the receiving application and your actual print dimensions determine what is used.

Will EXIF rotation affect the calculation?＋

Orientations 5–8 swap display width and height. Supported orientation fills the pixel fields using display dimensions. If orientation cannot be read consistently, stored axes remain and a warning is shown.

Are files uploaded, resized or saved back?＋

No. The tool reads supported local headers in a browser worker and creates a separate numeric report. The original image bytes and metadata are not changed.