How to Resize Photos: Pixels, DPI and Print Size Explained

To resize a photo, you change its pixel dimensions: width and height measured in pixels. That number controls how sharp the image looks on screen and, together with DPI, how large it can be printed. For the web and email you usually shrink the longest edge to somewhere between 1080 and 2000 pixels. For print you work backwards from the physical size: inches multiplied by 300 gives the pixels you need.

Most confusion about how to resize photos comes from mixing up three separate ideas: pixels, DPI and physical size. This guide separates them, gives you a table of exact numbers, and walks through resizing for each common destination.

Pixels, DPI and Physical Size: What Each One Means

Pixels are the actual data in your image. A 4000 x 3000 photo contains 12 million of them (12 megapixels). This is the only number that describes how much detail the photo holds.

Physical size is how big the image appears on paper or on a screen, in inches or centimetres. A file has no physical size on its own, it only gets one when it is displayed or printed.

DPI (dots per inch, sometimes called PPI for pixels per inch) is the bridge between the two:

physical size (inches) = pixels / DPI
pixels needed          = inches x DPI

DPI is stored as a small metadata tag in the file, but it does nothing on a screen. A monitor shows every pixel as a pixel regardless of the tag. The tag only matters when software or a printer decides how large to make the print.

Here is the same photo under different DPI tags. The pixels never change:

The real question for printing is not "what DPI is my file" but "do I have enough pixels for the size I want at a good DPI". We cover that next.

Pixel Sizes for Common Print Sizes at 300 DPI

300 DPI is the usual target for photo prints viewed at arm's length. For large prints viewed from further away, such as posters, 150 DPI is often acceptable. Here are the pixel counts you need:

Metric sizes are converted at 25.4 mm per inch and rounded to the nearest pixel.

A worked example

You have a 6000 x 4000 photo from a 24-megapixel camera and want an 8 x 10 inch print.

1. Pixels needed at 300 DPI: 2400 x 3000 (3000 x 2400 in landscape). You have more than enough, so no enlargement is needed.
2. Check the aspect ratio. Your photo is 3:2 (1.5). An 8 x 10 print is 5:4 (1.25). They do not match, so something must be cropped.
3. Keep the full height of 4000 px. At 5:4 the width becomes 4000 x 1.25 = 5000 px. You lose 1000 px of width, about 17 percent of the frame.
4. A landscape 10 x 8 inch print needs 3000 x 2400 pixels at 300 DPI. Your 5000 x 4000 crop is well above that, so you can scale it down to 3000 x 2400 (or leave it as is, since the lab will scale it anyway).

The lesson: aspect ratio mismatch costs you more of the picture than resolution does. Decide on the crop before you decide on the size.

Resizing Photos for Web, Email and Social Media

For screens, forget DPI entirely. Only pixel dimensions matter. The numbers below are practical starting points, not official standards. Platforms change their guidelines and re-compress uploads, so confirm the current recommended sizes in the platform's own help pages.

Two rules cover most cases. First, never upload more pixels than the destination will ever display. A 6000 px photo shown in an 800 px column wastes bandwidth and slows the page. Second, keep the original. Resize a copy.

For more on balancing size and quality after resizing, see How to Compress Images Without Losing Quality.

How to Resize a Photo Step by Step

You can do this in any editor, but a browser tool is the fastest route for one-off jobs. Here is the process with FileCrank's Photo Resizer:

1. Decide your target. Write down the pixel dimensions from the tables above. If you only know the print size, multiply inches by 300.
2. Upload the photo. The tool accepts JPG, PNG, WebP and TIFF files up to 50 MB.
3. Pick a resize mode. There are three:
   • Pixels: enter exact width and height.
   • Percent: scale to a percentage of the original, for example 50 percent.
   • Longest edge: set the maximum for whichever side is longer. This is the easiest option for a mixed batch of portrait and landscape photos because both end up with the same maximum dimension.
4. Decide about EXIF. The "Preserve EXIF" checkbox is on by default. Untick it if the photo is going somewhere public (more on this below).
5. Download the result and open it to check it. Zoom to 100 percent and look at edges and text.

Photo Resizer accepts dimensions up to 10,000 px. If you need to fit an image into an exact box with a specific behaviour, the simpler Resize Image tool takes a width, a height and a fit mode: contain keeps the whole image inside the box, cover fills the box and crops the overflow, and fill stretches the image to the exact size, ignoring its proportions. Its maximum is 8,000 px per side.

Setting DPI for print

If a print portal or lab rejects your file for "low resolution" and the pixel count is actually fine, the DPI tag may simply be 72 or missing. FileCrank's DPI Converter rewrites that tag to 72, 96, 150, 300 or 600 without resampling, so the pixels stay identical.

Use it when you already have enough pixels. It cannot rescue a small image. A 1200 x 800 photo tagged at 300 DPI still only prints well at 4 x 2.7 inches.

Common Mistakes When Resizing Photos

Mistake 1: Upscaling and expecting detail

When you enlarge a photo, software has to invent the new pixels. Interpolation (bilinear, bicubic, Lanczos) averages neighbouring pixels to fill the gaps. The result is smooth but soft. Doubling an 800 x 600 image to 1600 x 1200 gives you a bigger file, not a sharper picture. Dedicated AI upscalers can add plausible texture, but what they add is generated, not recovered from the scene.

If you must enlarge, do it once, in a single step, and keep the enlargement modest. Repeated small enlargements compound the softness.

Mistake 2: Breaking the aspect ratio

Entering a width and height that do not match the original proportions stretches the photo, so faces look wide and circles turn into ovals. Either enter only one dimension and let the other follow, use longest-edge or percent mode, or crop deliberately to the new ratio. The common ratios to know:

• 3:2, most DSLR and mirrorless cameras, and a 4 x 6 print
• 4:3, most phones and compact cameras, and many tablets
• 5:4, 8 x 10 and 16 x 20 prints
• 16:9, video and widescreen displays
• 1:1, square social posts

Mistake 3: Confusing DPI with quality

Many people believe a 300 DPI image is "high quality" and a 72 DPI image is "low quality". Neither is true. A 6000 x 4000 photo tagged 72 DPI contains exactly the same pixels as the same file tagged 300 DPI. Judge a file by its pixel dimensions.

Mistake 4: Resizing repeatedly from a JPEG copy

Each time you save a JPEG you apply lossy compression again. Resizing a resized copy of a resized copy slowly degrades the image. Always go back to the original (or a lossless master such as TIFF or PNG) and resize once.

Mistake 5: Ignoring metadata

Photos from phones and cameras carry EXIF data: camera model, date and time, exposure settings, and often GPS coordinates. Whether this survives a resize depends on the tool. FileCrank's Photo Resizer preserves EXIF by default, which is helpful for archives and for photographers who want copyright information kept, but not helpful if you post a photo taken at your home. Untick the option when sharing publicly, and read What Is EXIF Data and How to Remove It to see exactly what a photo can reveal.

Also remember that social platforms often strip or alter metadata on their own, so you should not rely on them to protect your privacy.

Mistake 6: Compressing before resizing

Order matters. Resize first to the target pixel size, then adjust compression or quality if the file is still too large. Compressing a huge image and then shrinking it wastes effort and can introduce artefacts that become more visible at the smaller size.

A Quick Checklist Before You Export

• Do I know the destination (screen or print) and its target pixel size?
• Does the aspect ratio match, or have I chosen my crop on purpose?
• Am I resizing from the original, not a previous export?
• Am I shrinking rather than enlarging?
• Have I decided whether to keep or remove EXIF data?
• For print: do I have inches x 300 pixels (or inches x 150 for large, distant prints)?
• Have I opened the result at 100 percent to check it?

Limits of Browser-Based Resizing

A few honest notes. Online tools work from the file you upload, so very large originals take longer to transfer, and FileCrank's tools have a 50 MB upload limit per file. RAW camera files are not an input here: export a JPG, PNG or TIFF first. And for a professional print job, labs sometimes require a particular colour profile such as sRGB or a specific file format. Check their upload requirements before you start.

Uploaded files on FileCrank are deleted automatically, in about an hour. If a photo is truly sensitive, resize it with software installed on your own device instead.

Conclusion

Resizing a photo is simple once you keep the three concepts apart. Pixels are the detail in the file. DPI is a label that decides print size. Physical size is the result of dividing one by the other. For screens, pick pixel dimensions and ignore DPI. For prints, multiply the inches by 300 and make sure you have at least that many pixels before you crop.

Ready to try it? Open the Photo Resizer to set exact pixels, a percentage or a longest edge, then use the DPI Converter if your print portal wants a specific DPI tag. No sign-up is needed.