How to resize a photo or signature to 20 KB
Last updated 2026-10-05
Exam and job application forms often ask for a passport photo under 50 KB and a signature under 20 KB. A phone photo is several megabytes, so the picture has to shrink about a hundred times. That is possible, but the order you do things in makes a big difference to how it looks.
Start with the right picture
Crop to the shape the form wants before you compress anything. A picture that contains extra background spends bytes on it. For a signature, sign in dark ink on plain white paper, photograph it in even light, and crop tightly around the signature; a clean white background compresses far smaller than a shadowy one.
For a photo, use a plain background and even lighting for the same reason. Detail is what costs bytes: sharp hair, patterned clothes and noisy low-light shots are the hardest to fit into a small file.
Use the Target file size tab
In Image Resizer, add the image and choose Target file size. Enter the limit in KB. The tool saves the picture as JPEG and searches for the highest quality that still fits under your number; if even the lowest quality is too big at the original dimensions, it reduces the pixel dimensions and tries again, then reports the size it reached.
Sizes use 1 KB = 1,000 bytes, which matches most upload forms, so a result of 49 KB passes a 50 KB limit. Aim a few KB under the number to be safe.
If the form also wants exact dimensions
Some forms specify pixels as well as size, for example 200 × 230. Use the Dimensions tab with Exact size, which scales the picture to cover the target and trims the overflow from the centre rather than stretching it. Do that first, then run the target-size step on the result. Make sure the face or signature sits in the middle of the frame before you do, because the crop is centred.
Choosing the format
Pick JPG unless the form says otherwise. JPEG is the format almost every portal accepts, and it has no transparency, so a PNG with a see-through background loses that background and can come out black. If the original is a PNG screenshot with large flat areas, PNG may already be small; check before converting.
iPhone HEIC photos are decoded in the browser, so you can drop them straight in and save as JPG.
Check the result
Open the downloaded file and look at it at full size. At 20 KB some softness is normal; what matters is that the signature strokes are continuous and the face is recognisable. If it looks too rough, ask for a larger limit if the form allows, or retake the photo with simpler lighting and a plain background rather than lowering quality further.