Compress Image to 25KB — Free, Fast & Private
25 KB is a number that sits between the signature rules rather than on one of them. It is safely inside CTET’s band, a long way inside GATE’s, and outside the bands of the three largest recruitment portals — in opposite directions. Get the form right before you get the file size right.
What fits in 25 KB — measured on this page
We dropped five real files on the compressor above and kept what it handed back. 5 of 5 came out under 25 KB; 3 were made smaller in pixels to get there, because past a point the bytes can only come from pixels.
| File | Before | After, on this page | Under 25 KB? |
|---|---|---|---|
| 12 MP phone photo | 4032 × 3024 px · 3.73 MB | 1429 × 1072 px · 17.9 KB | Yes |
| Portrait / headshot | 3264 × 4653 px · 2.25 MB | 1632 × 2327 px · 23.8 KB | Yes |
| Scanned handwritten page | 3349 × 4281 px · 2.17 MB | 1675 × 2141 px · 23.7 KB | Yes |
| Scanned signature | 2041 × 617 px · 109.1 KB | 2041 × 617 px · 24.2 KB | Yes |
| Screenshot (PNG) | 1280 × 800 px · 88.1 KB | 1280 × 800 px · 24.3 KB | Yes |
Measured 2026-10-06 in Chromium 145.0.7632.6 with this page’s own settings. The photos are public-domain and CC0 files from Wikimedia Commons; the screenshot is our own. Sizes read as the tool shows them (1 KB = 1,024 bytes); the target itself is 25,000 bytes, which is under 25 KB on either reading.
Three signature rules, three different verdicts
Each row below is read from the exam body’s own document. The last column is plain subtraction against a 25 KB file.
| Signature for | Band | A 25KB file |
|---|---|---|
| CTET | 3–30 KB | inside, 5 KB under the ceiling |
| GATE | 3–300 KB | inside, near the bottom |
| SSC (CGL, CHSL, GD, MTS) | 10–20 KB | too big, by 5 KB |
| IBPS PO / Clerk | 10–20 KB | too big, by 5 KB |
| RRB (ALP, NTPC, Group D) | 30–49 KB | too small, by 5 KB |
If you are applying to SSC, IBPS or SBI, a 25 KB signature will be over their 20 KB limit — use the 15KB page, which aims at the middle of their band. If you are applying to the railways, a 25 KB file is under RRB’s 30 KB floor and fails for being too small; the RRB signature tool aims inside 30–49 KB. This page is for CTET, for GATE if you want a modest file, and for anything else whose ceiling is above 25 KB.
Why not go right up to CTET’s 30KB?
Because the edge is the one place where two honest systems can disagree. This page’s target counts a kilobyte as 1,000 bytes, so its 25 KB target means at most 25,000 bytes. Some upload checks count a kilobyte as 1,024 bytes, which reads the same file as 24.41 KB and moves CTET’s ceiling to 30,720 bytes. Either way, 25,000 is under it with room to spare — a file aimed at the ceiling itself has none.
CTET’s floor is generous, 3 KB, so the low end rarely bites. The target on this page is a ceiling only and the tool never pads a file upward, so a small, tightly cropped signature can come out well under 25 KB. For CTET that is fine as long as it stays above 3 KB.
What 25,000 bytes means for a signature’s pixels
CTET states the signature as a print size, 3.5 × 1.5 cm, rather than in pixels. GATE does give pixels: at least 250 × 80 and at most 580 × 180. That is 20,000 to 104,400 pixels, so 25,000 bytes is 1.25 bytes per pixel at the small end and 0.24 at the large end. An uncompressed colour pixel is three bytes, so even the larger figure leaves a generous budget for what is mostly white paper.
The practical consequence: at 25 KB a well-cropped signature does not need to be crushed. Keep the strokes crisp. If the result shows grey halos around the ink, the cause is almost always a scan that was too large or too dim, not a target that was too small — crop tighter to the strokes, shoot in even daylight, and run it again.
Turning CTET’s centimetres into pixels
A print size only becomes a pixel size once you choose a resolution, because pixels ÷ DPI = inches, and an inch is 2.54 cm. CTET does not name a resolution, so here is the arithmetic at three common scanner settings for its 3.5 × 1.5 cm box:
- at 100 DPI: 138 × 59 pixels, or 8,142 pixels, giving 3.07 bytes per pixel at 25 KB
- at 200 DPI: 276 × 118 pixels, or 32,568 pixels, giving 0.77 bytes per pixel at 25 KB
- at 300 DPI: 413 × 177 pixels, or 73,101 pixels, giving 0.34 bytes per pixel at 25 KB
None of those is a CTET requirement — they show how quickly the budget per pixel falls as the scan resolution climbs. A phone photo of a signature is usually far larger than any of them, so cropping and resizing down to a sensible size before compressing keeps the 25 KB for the ink rather than for empty paper. If you are not sure what resolution a file claims, the DPI checker reads it.
A photo can use this size too
IBPS and SBI take a photograph of 20–50 KB (SBI: 20–50 KB) and prefer 200 × 230 pixels. 25 KB sits inside that band, near its lower end. Over 46,000 pixels, 25,000 bytes is 0.54 bytes per pixel — less per pixel than a signature gets, because a face carries more detail in every block.
The tool reaches the target in a fixed order. It lowers JPEG quality at your image’s full size first, keeping the highest quality that fits. Only when even the lowest quality still misses does it reduce the pixel dimensions, and it tells you and shows the new size when it does. The measured table near the top of this page shows how each sample went. For a photo that must be exactly 200 × 230, crop to that shape first so the dimensions are already settled; the IBPS photo tool handles the whole job.
Everything runs in your browser. The signature or photo never leaves your device — and the signature guide covers each exam’s rules in more detail.
If the form gives a minimum as well as a maximum, see compress image between 20KB and 50KB.