How to Compress an Image to 100 KB, 50 KB or 20 KB for Forms and Uploads

What do 100 KB, 50 KB and 20 KB mean?

KB stands for kilobyte, and MB stands for megabyte. One megabyte is about 1,000 kilobytes, so 100 KB is roughly a tenth of a megabyte. A photo from a modern phone is often 3 to 5 MB, which means that to reach 100 KB it has to become 30 to 50 times smaller.

That sounds like a lot, but a form field does not need a big picture. A face or a signature looks fine on a screen at a small size, and a small file uploads faster and fits the limit.

Why a picture is large in the first place

Two things decide the size of a picture file: the number of pixels, which is its width times its height, and how strongly the pixels are compressed. A photo of 4000 by 3000 pixels has 12 million pixels. If you shrink it to 1000 by 750, it has 750,000 pixels, which is 16 times fewer, and the file shrinks a great deal with it.

This is why you should change the size in pixels first and the quality second. Lowering the quality alone on a huge picture makes it look bad before the file is small enough.

Step-by-step: compressing an image to a target size

• Step 1: Add your picture. Open the Image Compressor and drag your picture into the box. You can add up to 20 images at a time, up to 25 MB each.
• Step 2: Set a maximum width. Start with a width that fits the purpose, for example 1000 pixels for a photo or 800 pixels for a document. The height follows automatically.
• Step 3: Choose the format. Use JPG or WebP for photos. If the form accepts only JPG, choose JPG.
• Step 4: Set the quality. Start at about 75 percent and look at the size shown for the result.
• Step 5: Adjust and check. If the file is still above your limit, lower the quality by 5 or 10 points, or lower the width a little, and check the new size. Repeat until it is just under the limit.
• Step 6: Download and test. Download the picture, and if you can, open it to check that the face, the text or the signature is still clear.

Rough settings for 100 KB, 50 KB and 20 KB

Every picture is different, because a photo with a plain background compresses much better than one with a lot of detail. Treat these as starting points and always check the size that the tool shows.

• Around 100 KB. Try a maximum width of about 1000 pixels and a quality of about 70 percent.
• Around 50 KB. Try a maximum width of about 800 pixels and a quality of about 60 percent.
• Around 20 KB. Try a maximum width of about 500 pixels and a quality of about 50 percent. Expect a smaller, softer picture.
• Still too large. Lower the width first. It saves more space than lowering the quality again.

Which format gives the smallest file?

• JPG. The standard choice for photos, accepted almost everywhere. Use it when a form asks for a JPG or JPEG file.
• WebP. Usually smaller than JPG at a similar look, but not every upload form accepts it. Use it for websites, not for forms that list allowed formats.
• PNG. Best for logos, screenshots and pictures with transparency, but its files are larger, so it is a poor choice for hitting a small size.

Passport-size photos, signatures and scanned documents

• Passport-size and profile photos. A small width is enough. Keep the face clear and the background plain, which also makes the file smaller. Check the width and height that the form asks for, and use the Image Resizer if you need an exact size.
• Signatures. A signature on a white background compresses very well and can often be made very small. Keep the contrast high so that the lines stay clear.
• Scanned documents. Text needs a higher quality than a face to stay readable. If the text turns fuzzy, raise the quality a little and lower the width less.

Tips for a clean result

• Resize first, compress second. Setting a smaller width before you lower the quality keeps the picture sharper at the same file size.
• Crop out empty space. A picture with less background has fewer pixels to store.
• Start from the original. Compress from your first copy. Compressing an already compressed picture again makes it worse.
• Keep your originals. Compression cannot be undone, so store the original files in a safe place.
• Read the form's rules. Check the allowed formats and the minimum and maximum size before you upload, because some forms also ask for a minimum size.

Common problems and fixes

• The picture is still too large. Lower the maximum width, then lower the quality a little more. A smaller number of pixels makes the biggest difference.
• The picture looks blurry. The quality or the width is too low. Raise one of them a little and check the size again.
• My PNG does not get small. PNG is lossless, so it cannot shrink as much. Save the picture as JPG if it has no transparency.
• The form refuses my file. Check the file type. Some forms accept only JPG or PDF and reject WebP and PNG.
• The file is now too small. Some forms also ask for a minimum size. Raise the quality or the width a little until the size is inside the allowed range.

Related tasks

• Set an exact width and height. Use the Image Resizer when a form asks for an exact size in pixels.
• Make a PDF from your pictures. Use the JPG to PDF tool when a form wants a PDF and not a picture.
• Join PDF files. Use the Merge PDF tool to combine several documents into one file.

Compress your image now

Add your picture in the Image Compressor, set a width and a quality and watch the size until it fits your limit. Everything happens in your browser, so your pictures are never uploaded. It is free, adds no watermark and needs no signup.

Frequently asked questions