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How to reduce image size in KB

To reduce image size in KB, lower the JPEG quality, shrink the pixel dimensions, or both, then check the new size before you upload. A free tool like RealScaner Compress Image does this from a target you type: pick 50 KB, 100 KB, or a custom number, and it searches for the best quality that fits. The photo is processed in your browser and is never uploaded.

The usual reason you are here: an exam, job, visa, or passport portal rejected your photo with "file size must be between 20 KB and 50 KB." Your phone shot a 3 MB picture. This post is the KB answer. For cropping faces, receipts, and ID scans so they stay readable, see the companion guide compress photos for forms.

What decides an image's size in KB

Two levers control almost all of it.

• Pixel dimensions. A 4000 by 3000 photo has 12 million pixels. A 400 by 300 copy has 120,000. Fewer pixels means less data to store, so the file drops fast.
• Compression quality. JPEG and WebP throw away detail the eye is unlikely to miss. A lower quality setting throws away more, and the file gets smaller. Push it too far and you see blocks and smeared edges.

Format matters too. A photo saved as PNG is usually far bigger than the same photo as JPEG, for reasons covered below. Cropping helps for the same reason resizing does: a tight crop has fewer pixels to store.

What real application forms ask for

Forms state a KB range and sometimes a pixel or print size. Three official examples:

• India, Staff Selection Commission. A notice from the SSC Karnataka Kerala Region office, dated December 7, 2022, repeats the CHSL 2022 rules: a colour photo in JPEG format, 20 KB to 50 KB, about 3.5 cm wide by 4.5 cm high, and a scanned signature in JPEG, 10 KB to 20 KB, about 4.0 cm by 2.0 cm. It says blurred photos or signatures will be rejected.
• US Diversity Visa entry. The State Department's photo requirements page says the DV image must be a JPEG, equal to or less than 240 kB, square, and 600 by 600 pixels.
• US online passport renewal. The State Department's "Uploading a Digital Photo" page, updated May 4, 2026, accepts JPG, JPEG, PNG, HEIC, or HEIF files between 54 KB and 10 MB, and lets you crop during upload.

Notice that two of these set a minimum as well as a maximum. A photo crushed to 15 KB fails the SSC rule just as surely as a 3 MB one. Always read the current notice for your exam or portal, because each cycle can change the numbers.

KB vs KiB: why 50 KB is not always 50 KB

The SI prefix kilo means 1,000. Computers long used it to mean 1,024, and NIST explains that the binary prefix kibi (KiB) was created to mean exactly 1,024. So "50 KB" can mean 50,000 bytes or 51,200 bytes, depending on who wrote the portal.

Your devices can disagree too. Apple's support page on storage says storage makers measure in decimal, and that older systems such as iOS 10 and OS X Leopard reported storage in binary. So the same file can show a slightly different KB number on a Mac, a Windows PC, and the portal.

RealScaner counts 1 KB as 1,000 bytes, so its 50 KB preset never goes above 50,000 bytes. That passes a portal using either definition. Other tools may count 1,024, so when you use a different app, aim a few KB under the cap, for example 48 KB for a 50 KB limit.

How to check photo KB on your phone or computer

iPhone

Open the photo in the Photos app, then swipe up or tap the Info button. Apple's iPhone User Guide lists "camera metadata such as lens, shutter speed, file size, and more" among the details. In the Files app, touch and hold a file and choose Get Info, or sort a folder by Size.

Android

In Google Photos, open the photo and swipe up. Google's help page says that is where you check backup quality and size, under Details. Your phone's file manager also shows the size of a saved image.

Windows

In File Explorer, select View, then Details, and the Size column appears. Right-click a file and choose Properties for the exact byte count. The Details tab in Properties shows the width and height in pixels.

Mac

Select the file in Finder and choose File, then Get Info, or press Command-I. Apple says the Finder's "Show item info" option in Icon view can show file size and image dimensions under each icon.

How to reduce image size in KB with RealScaner

1. Open Compress Image on your phone or computer.
2. Drop in up to 10 JPEG, PNG, or WebP images. Each one gets the same target but is processed on its own.
3. Under Target size per image, choose 50 KB, 100 KB, 200 KB, 500 KB, or 1 MB. For anything else, choose Custom and type a number from 1 to 10,240 KB.
4. Set Output format to JPEG for exam and visa forms. Auto also picks JPEG for ordinary photos, but switches to WebP or PNG if the image has transparency.
5. Tap Compress images, then read the result line. It shows the old and new size and a badge: Target met, Original, or Smallest.
6. Download. One image saves as a file. A batch saves as a ZIP.
7. Check the KB and pixel size on your device, then upload.

Behind the scenes, the tool tries lower JPEG or WebP quality first and keeps the highest quality that fits. It reduces the pixel dimensions only when needed, and it keeps the original aspect ratio. If your file is already below the target, it comes back untouched, labeled Original.

Compress image to 20KB or 10KB: when the target is too small

For 10 KB or 20 KB, choose Custom and type the number. Small targets are where honest tools and pretend tools part ways.

RealScaner labels every result. It lowers JPEG quality as far as 0.35 on the browser's 0 to 1 scale and keeps the short side of the image at 320 pixels or more. When a photo needs more than that to fit, you get the smallest file at those settings, clearly labeled Smallest, so you always know where the file stands.

If you see Smallest, crop first. For an exam photo, crop to head and shoulders. For a signature, sign in dark ink on plain white paper, photograph it, and crop tight around the ink. The RealScaner scanner can do that crop: drag the corners to the edges of the signature and export JPEG, then run that file through Compress Image. Fewer pixels to start with makes 10 KB to 20 KB much easier to hit.

Also watch the other end. If the form says 20 KB to 50 KB and the result comes back at 14 KB, raise the target and run it again.

Why a PNG stays big

PNG is lossless. It keeps every pixel exactly, which is great for screenshots and logos and poor for photos. PNG has no quality setting, so a PNG gets smaller only by losing pixels. For a small KB target, choose JPEG output.

If you made a signature in Signature maker, it downloads as a transparent PNG. Forms usually want JPEG, so set Output format to JPEG in Compress Image. Transparent areas are filled with white, which is what a signature on paper looks like anyway.

How to reduce image size on iPhone

Open realscaner.com/compress-image/ in Safari and follow the same steps. Choose the photo from your library, set the target, and download.

An iPhone set to High Efficiency saves photos as HEIF. Convert those with HEIC to JPG, which also runs on your device, then compress the JPG. To stop it happening with new photos, Apple's support page explains the fix: open Settings, tap Camera, tap Formats, then tap Most Compatible. New photos are then saved as JPEG. Other ways to convert are in how to convert HEIC to JPG.

How to reduce image size without losing quality

Some loss is the price of a smaller file. You can keep it out of sight:

• Start from the original photo, not a copy that was already compressed or sent through a chat app.
• Crop away walls, tables, and sky before compressing. That removes pixels nobody needed.
• Use the largest target the form allows. A 200 KB limit does not need a 50 KB file.
• Zoom in on the result. If eyes, text, or signature strokes look smudged, crop tighter and try again rather than dropping the target further.

On a Mac, Preview can also cut the size: Apple says to choose Tools, then Adjust Size, select Resample image, and enter a smaller Resolution, and the new size is shown at the bottom of the window.

More tools for form photos

• For a fixed size, such as 600 by 600 pixels or 3.5 by 4.5 cm, use Resize Image, which sets exact pixels or cm and a minimum and maximum KB in one pass.
• For a photo under a minimum, like the passport renewal's 54 KB, Resize Image takes a minimum KB too.
• A file already under the target comes back untouched, in its original format. To turn a small PNG into a JPEG, set a custom target just below its current size.
• Face, background, and age rules come from the notice, so check the photo against it before you upload.
• Compress Image takes JPEG, PNG, and WebP images. Convert HEIC photos with HEIC to JPG first.
• WebP output is smaller, but many government portals list only JPEG. Use what the form lists.

Files stay on your device while they are processed. For what that means in practice, read what stays on your device with browser document tools. If the portal wants a PDF instead of an image, see how to turn a photo into a PDF and how to compress a PDF to 200KB.

Sources

• Notice on photograph and signature provisions, Combined Higher Secondary (10+2) Level Examination, 2022 (F. No. 04/19/2022-Exam), Staff Selection Commission (Karnataka Kerala Region), December 7, 2022
• Photo Requirements, U.S. Department of State, accessed October 2026
• Uploading a Digital Photo, U.S. Department of State, updated May 4, 2026
• Definitions of the SI units: The binary prefixes, NIST, accessed October 2026
• How storage capacity is measured on Apple devices, Apple Support, accessed October 2026
• See photo and video information on iPhone, Apple Support, accessed October 2026
• Find and view files and folders in Files on iPhone, Apple Support, accessed October 2026
• Using HEIF or HEVC media on Apple devices, Apple Support, December 5, 2025
• Choose the backup quality of your photos & videos, Google Photos Help, accessed October 2026
• Free up drive space in Windows, Microsoft Support, accessed October 2026
• Get file, folder, and disk information on Mac, Apple Support, accessed October 2026
• Crop, resize, or rotate an image in Preview on Mac, Apple Support, accessed October 2026

Key takeaways

• Image file size in KB depends on two things you control: the pixel dimensions and the compression quality.
• An official SSC notice from December 2022 asked for a JPEG photo of 20 KB to 50 KB and a JPEG signature of 10 KB to 20 KB.
• One KB can mean 1,000 bytes or 1,024 bytes, so aim a few KB under a strict limit.
• RealScaner Compress Image offers 50 KB, 100 KB, 200 KB, 500 KB, and 1 MB presets plus a custom target from 1 KB to 10,240 KB.
• RealScaner labels every result Target met, Original, or Smallest, so you always know where the file landed.

Common questions

How do I reduce image size in KB?

Lower the JPEG quality, reduce the pixel dimensions, or both. In RealScaner Compress Image you pick a KB target, and the tool lowers quality first and keeps the full pixel size whenever quality alone reaches the target.

How do I compress an image to 50KB or 100KB?

Open RealScaner Compress Image, add the photo, choose the 50 KB or 100 KB preset, set the format to JPEG, and download. If the form also has a minimum size, check that the result did not land below it.

How do I reduce a photo size to 20KB?

Choose Custom and type 20, or a little less if the form counts 1,000 bytes per KB. Crop the photo to the face or signature first, so the pixels go to what matters. The compressor keeps the short side at 320 pixels or more and labels every result, so you see at once whether it reached 20 KB.

How do I check photo KB on my phone?

On iPhone, open the photo in Photos and swipe up or tap the Info button; Apple lists file size among the details. On Android, Google Photos says to swipe up on a photo to see its size under Details.

How do I reduce image size on iPhone?

Open realscaner.com/compress-image/ in Safari, choose the photo, pick a KB target, and download the JPEG. For a HEIC photo, convert it with RealScaner HEIC to JPG first, also on your device, or set Settings, Camera, Formats to Most Compatible so new photos save as JPEG.

Can I reduce image size without losing quality?

Not by much. Lossless PNG keeps every pixel but rarely gets small, and a real KB cut comes from fewer pixels or stronger JPEG compression. Cropping away background is the cut that costs the least visible detail.

Published October 21, 2026. Updated October 21, 2026.

Keep reading

• How to compress a PDF to 200KB, 100KB, or 1MB

  Use the Smaller preset, cut extra pages, and check the real size. Why some PDFs can't reach 100KB, and what to do.

• How to turn a photo into a PDF

  Import the photo into RealScaner, mark the page edges, and download a PDF. Works on iPhone, Android, Windows, and Mac.

• How to create an electronic signature for free

  Draw or upload your signature, remove the background, and download a transparent PNG to sign PDFs and forms.

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