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Quick answer
To resize an image to a specific size in KB, open Resize Image, choose Pixels, pick a width from the chart below for your target, set the format to JPG and click Resize image. The new size in KB is shown. If it is over your limit, reduce the width by 10–20% and try again.
How to resize an image to any KB size in 3 steps
Add your image
Open Resize Image and drop in the photo.
Pick a width from the chart
Choose Pixels, enter a width that matches your KB target, and set the format to JPG.
Check and adjust
The new size is shown. Under your limit? Download it. Over? Reduce the width a little and resize again.
KB target chart
These are typical sizes for JPG photos. Busy, detailed pictures land at the higher end.
Swipe to compare →
| Target | Width to try | Guide |
|---|---|---|
| 20KB | 250–300 px | Resize to 20KB |
| 50KB | 400–500 px | Resize to 50KB |
| 100KB | 600–800 px | Resize to 100KB |
| 200KB | 1000–1200 px | Resize to 200KB |
| 500KB | 1600–2000 px | Most photos, lightly compressed |
Why KB depends on more than pixels
- Detail: a photo of grass or text has more detail to store than a plain wall, so it is bigger at the same size.
- Format: JPG is small for photos, PNG is large. Always use JPG for a small KB target.
- Compression: the File size option squeezes the same pixels into fewer KB. Use it when the dimensions must stay fixed.
Common KB limits and what they're for
Swipe to compare →
| Limit | Usually for |
|---|---|
| 20KB | Signatures and tiny thumbnails |
| 50KB | Profile and ID photos on forms |
| 100KB | Document photos and headshots |
| 200–240KB | Detailed photos, including the US visa (DS-160) photo |
| 500KB and up | Listings, portfolios and website images |
If a form gives both pixel dimensions and a KB limit, meet the pixels first, then reduce the KB with compression.
How to check an image's size in KB
- iPhone: in Photos, open the picture and swipe up, or tap the i button, to see its size. In Files, touch and hold and choose Get Info.
- Android: in Google Photos, open the picture and swipe up for details.
- Mac: select the file in Finder and press Command-I.
- Windows: right-click the file and choose Properties.
Zappy shows the new size on screen after resizing or compressing, so you can confirm it before downloading.
When the dimensions must stay the same
Some forms ask for exact pixels and a KB limit, such as 600 × 600 and under 100KB. Resize to the exact pixels first, then use the File size option (or Compress Image) on Medium or Extreme to bring the KB down.
Frequently asked questions
How do I resize an image to a specific size in KB?
Resize it to a smaller width in pixels as a JPG, check the new KB shown, and adjust the width until it is under your target.
How do I reduce an image to 100KB without changing its dimensions?
Use the File size option in Resize Image, or Compress Image on Medium or Extreme. Both keep the pixels the same and shrink the file.
Why is my image still too big after resizing?
It may be saved as PNG, or very detailed. Switch to JPG and reduce the width by another 10 to 20 percent.
Is 1 MB 1,000 KB or 1,024 KB?
Upload forms usually treat 1 MB as 1,000 KB. Aim a little under your limit to be safe either way.
What's the fastest way to hit a KB limit?
Resize to a smaller width as a JPG. Reducing pixels shrinks the file far more than compression alone.
Does it work on iPhone?
Yes. Open Resize Image in Safari and pick the photo from your library.
Is my photo uploaded?
No. Resizing happens in your browser, so the photo stays on your device.