Image Aspect Ratio Calculator

What the calculator shows

After you load an image, the page displays its width, height, simplified ratio and megapixels. The ratio is reduced by dividing both dimensions by their greatest common divisor, so 1920 by 1080 becomes 16:9 and 1200 by 1200 becomes 1:1.

A ratio analysis panel lists common ratios and marks the closest match. The chips are a quick reference, not a strict classification. An image with a ratio close to 3:2 may be labelled that way even if its exact reduced ratio is 1499:1000.

A print sizes table shows the physical dimensions at 72, 150, 300 and 600 DPI. These are calculated from the pixel dimensions, so a 3000-pixel-wide image is about 41.7 inches at 72 DPI and about 10 inches at 300 DPI.

How to analyze an image

1. Drag a JPG, PNG, GIF, WebP or SVG onto the drop zone, or click Browse Files.
2. Wait for the preview and the four stat cards to fill in.
3. Read the simplified ratio and the common-ratio chips.
4. Check the megapixel count if you need to know the camera resolution.
5. Review the print sizes at the DPI values that matter for your job.
6. Use Copy to save the dimensions, ratio and MP as text.

The preview is contained in a square frame, so it may not show the image at its true proportions. Trust the numeric dimensions, not the thumbnail.

Using the resize calculator

Lock Aspect Ratio is on by default. Enter a new width and the height updates to preserve the ratio. Enter a new height and the width updates. The result line shows the new dimensions in pixels.

If you turn the lock off, you can enter both values independently. That changes the ratio and can distort the image if you actually resize it later with an editor. Use the unlocked mode for planning a crop or a layout, not for a proportional resize.

The calculator does not resize the file. It only calculates numbers. To apply the dimensions, use an image editor or a dedicated resizer.

Common ratios and where they fit

• 1:1: square posts, profile photos, product tiles.
• 4:3: older cameras, presentations, standard monitors.
• 3:2: many DSLR and mirrorless photos, 6 by 4 inch prints.
• 16:9: widescreen video, modern displays, YouTube thumbnails.
• 16:10: some laptops and monitors.
• 21:9: ultrawide screens and cinematic crops.
• 2.35:1: anamorphic cinema.
• 3:4, 2:3, 9:16: portrait versions of the common landscape ratios.

A ratio is not a size. A 1920 by 1080 image and a 3840 by 2160 image are both 16:9. The second has more pixels and can print larger at the same DPI.

Megapixels and print sizes

Megapixels are calculated by multiplying width by height and dividing by one million. A 6000 by 4000 image is 24 MP. More megapixels usually mean more detail, but lens quality, focus and compression matter too.

The print table divides the pixel dimensions by the DPI to estimate physical size. A 300 DPI print uses more pixels per inch than a 150 DPI draft, so the same file prints smaller. The table is a planning aid, not a guarantee that the print will look sharp at that size.

For a photo, 300 DPI is a common target for close viewing. For a large poster viewed from a distance, a lower DPI can be acceptable. Ask the printer for its requirement.

Limits and privacy

The page accepts JPG, PNG, GIF, WebP and SVG. It reads the image locally with the FileReader API, so the file is not uploaded. A very large image may take a moment to decode, but the analysis itself is lightweight.

SVG dimensions can be ambiguous because the file may use a viewBox without fixed width and height. The browser reports the rendered size, which may not match the intended print size. Check the SVG source if the numbers look unexpected.

The tool does not crop, rotate, convert or save the image. It does not evaluate composition, sharpness or colour. It is a calculator and a quick reference, not a photo editor.

Practical uses

• Social media: check whether a crop will fit a square or vertical post.
• Printing: estimate the physical size of a photo at 300 DPI.
• Web design: plan a responsive image that keeps its ratio.
• Video thumbnails: confirm a 16:9 frame.
• Scanning: compare a scan's ratio with the original document.
• Resizing: calculate a proportional width for a form.

Cropping to a ratio

Changing the canvas to a new ratio usually means cropping, not stretching. If you have a 3:2 photo and need a 1:1 profile image, crop the sides rather than squashing the width. The calculator tells you the target ratio, but it does not perform the crop.

To plan a crop, decide which dimension is fixed. For a square from a 6000 by 4000 image, the height is the limiting side, so the crop is 4000 by 4000. For a 16:9 banner from the same image, the width is fixed and the height becomes 3375 pixels. Use the resize calculator with the lock on to see the proportional numbers.

Keep the important subject inside the crop. A ratio calculation cannot tell you whether a face or a product is centred. Preview the crop in an editor before exporting.

Choosing dimensions for the web

A large pixel count is not always better. A 24 MP photo displayed at 800 pixels wide is wasting bandwidth. Resize to roughly twice the display width for high-density screens, then compress. The ratio stays the same; only the pixel count changes.

For a hero image, a 16:9 or 21:9 crop often fits the layout. For a product grid, a 1:1 or 4:5 crop is common. For a blog thumbnail, 3:2 or 16:9 works well. Match the ratio to the container rather than forcing the container to fit an arbitrary photo.

Use the print table only for print planning. A screen does not care about 300 DPI; it cares about pixels and CSS size. Mixing the two can lead to unnecessarily huge files.

Understanding the DPI table

The same pixel dimensions produce different physical sizes at different DPI values. A 3000 by 2000 image is 10 by 6.7 inches at 300 DPI, 20 by 13.3 inches at 150 DPI and about 41.7 by 27.8 inches at 72 DPI. The file has not changed; only the assumed print density has.

For a sharp print viewed closely, 300 DPI is a common target. For a poster viewed from several feet away, 150 DPI may be enough. For a billboard, even lower densities can work. Ask the printer for the expected viewing distance and file requirements.

If the table shows a physical size that is too small, you need more pixels, not a different DPI tag. Upscaling can help a little with modern algorithms, but it cannot recreate detail that was never captured.

Frequently Asked Questions