The fastest way depends on what you have installed

You can change a picture's file format in three ways: use the built-in tools on your computer, open the image in free software, or upload it to a web converter. Windows comes with Photos, which can save in JPEG, PNG, and BMP. Mac has Preview, which handles JPEG, PNG, TIFF, and others. If you need a format your computer doesn't support natively — like WebP or HEIC — free software like IrfanView (Windows) or XnConvert (both systems) works without installing anything complicated.

The method you choose depends on how many pictures you're converting and whether you want to keep the original. Converting one or two images takes under a minute with built-in tools. Converting dozens at once is faster with batch software. If you're converting to a format you've never heard of, a web converter lets you test it without downloading anything.

Key Takeaways

  • Windows Photos and Mac Preview can convert between common formats like JPEG, PNG, and BMP without installing extra software.
  • Right-click and "Save as" in most image programs lets you pick a new format, though the option name varies by software.
  • Free software like IrfanView and XnConvert handles less common formats and can convert many images at once.
  • Web converters like CloudConvert and Convertio work from any browser but upload your image to their servers, so avoid them for private photos.
  • The new file will be a different size and quality depending on the format — JPEG is smaller but loses detail, PNG keeps detail but takes more space.

Converting on Windows using Photos

Open the image in the Photos app (the default on Windows 10 and 11). Click the three dots in the top right, then select "Edit." In the top menu, click the three dots again and choose "Save as." A window opens asking where to save and what to name the file. At the bottom, you'll see a dropdown that says "JPEG image" or whatever format the original was. Click it to see other options: PNG, BMP, and GIF. Pick the format you want, then click "Save."

Photos will create a new file with the format you chose. The original stays unchanged. The new file appears in the same folder as the original. If you want to replace the original, you can delete it after checking that the new version looks right.

Converting on Mac using Preview

Open the image in Preview (the default image viewer on Mac). Click "File" in the top menu, then "Export." A save window opens. At the bottom, you'll see a dropdown labeled "Format" — it shows the current format. Click it to see options: JPEG, PNG, TIFF, PDF, and others depending on your macOS version. Select the format you want. Choose where to save the file, give it a name, then click "Save."

Preview creates a new file and leaves the original alone. If you're converting to JPEG, a slider appears asking about quality — move it right for better detail (larger file) or left for smaller file size (less detail). PNG doesn't have this option because it doesn't lose detail no matter what.

Using free software for formats your computer doesn't support

If you need to convert to WebP, HEIC, or another format your computer's built-in tools don't handle, download IrfanView (Windows) or XnConvert (Windows and Mac). Both are free and don't require installation on most systems. Open your image in the software, click "File" or "Export," pick the format from a dropdown, and save.

XnConvert also converts many images at once. Drag a folder of images into the window, pick your format, and click "Convert" — it processes all of them in seconds. This saves time if you're converting a camera's full memory card or a folder of screenshots.

Converting online with a web tool

Web converters like CloudConvert, Convertio, and Zamzar work from any browser without installing software. Go to the site, click "Upload" or drag your image into the window, pick the format you want from a dropdown, then click "Convert." The site processes the image and gives you a download link.

Web converters are useful for testing a format you've never used before, or for converting a single image on a computer where you can't install software. The downside is that your image uploads to someone else's server. For private photos, use your computer's built-in tools or free software instead. Most web converters delete uploaded files after a few hours, but there's no may provide.

Understanding what happens to your image when you convert

Different formats store images differently, and the change affects file size and quality. JPEG is smaller because it throws away some detail your eye might not notice — useful for photos you're sharing online. PNG keeps all the detail but makes a bigger file — better for images you might edit later or screenshots where text needs to be sharp. BMP is rarely used today because it makes very large files. GIF is for simple images or animations.

When you convert from one format to another, the image itself doesn't change — you're just repackaging it. Converting a JPEG to PNG doesn't add back the detail the JPEG lost. Converting a PNG to JPEG makes the file smaller but loses some sharpness. If you're unsure which format to use, JPEG works for photos and PNG works for everything else.

What to do if the format you want doesn't appear in the dropdown

If you're using Photos or Preview and the format you need isn't in the list, your computer's built-in tool doesn't support it. Download free software like IrfanView or XnConvert instead — they support dozens of formats. Open your image, go to File or Export, and look for the format in the dropdown. If it's still not there, the format is very specialized and you'll need a web converter or software designed for that specific format.

Before downloading anything, check what format you actually need. Sometimes a program asks for "JPEG" when it really means "any common image format" — in that case, JPEG, PNG, or BMP all work. If you're not sure, ask the person or program that requested the format.

Frequently Asked Questions

Will converting a JPEG to PNG make it sharper?

No. PNG is a container format — it doesn't add back detail that JPEG already removed. Converting a JPEG to PNG just stores the same blurry image in a different format. If you need a sharp version, you need the original file before it was converted to JPEG.

Can I convert an image to a smaller file size?

Yes, by converting to JPEG or by using software that lets you adjust quality. JPEG files are typically 5 to 10 times smaller than PNG for the same image. Most image software lets you choose a quality level when saving as JPEG — lower quality means smaller file, but more visible blurriness.

What's the difference between right-clicking "Save as" and using the File menu?

Right-click "Save as" works in some programs but not all — it depends on the software. Using File > Export or File > Save as is more reliable because it's built into almost every image program. If right-click doesn't show a format option, use the File menu instead.

Is it safe to upload my photos to a web converter?

Web converters are generally safe, but they do upload your image to someone else's server. Most delete files after a few hours, but there's no legal may provide. For private photos, use your computer's built-in tools or free software instead. For public images or screenshots, web converters are fine.

Can I convert a picture to PDF?

Yes. Mac Preview has PDF as a format option in the Export menu. On Windows, you can use free software like IrfanView or a web converter. Some programs also let you right-click an image and choose "Print to PDF," which creates a PDF file without opening image software.