Signature Resize

The form wants a signature of 10 to 20 KB, and what you have is a full-size phone photo: grey paper, a shadow, a small signature in the middle. A signature goes wrong in ways a portrait does not. It carries too much empty paper, the paper photographs grey, and the finished file is often too small for the form rather than too big.

Sign it on white paper, in black ink

IBPS and SBI ask for white paper and black ink, and Protean's PAN checklist says never to sign on a patterned or coloured background. Use a plain white sheet and a black pen, and sign the way you normally sign.

Some rules belong to one form:

• IBPS and SBI do not accept a signature in capital letters.
• SSC says: "Signature should be horizontally aligned." Sign along a level line.
• RRB has the signature made inside a box 35 mm wide and 20 mm high, so sign at that size.
• UPSC wants one sheet carrying three signatures.

Sign several times and photograph the cleanest; a blot survives any resizing.

Match the shape of the form's frame

Each preset puts the signature into a fixed frame of pixels. The signature is always fitted whole into that frame, never cropped, so any difference in shape becomes white margin on two sides. SSC's frame is 709 × 236 px, 3 to 1; IBPS and SBI's is 2.33 to 1, RRB's 1.76 to 1 and UPSC's three-signature frame 1.2 to 1. Where a notice gives centimetres, pixels = cm ÷ 2.54 × DPI, rounded: SSC's 6.0 cm at 300 DPI is 709 px.

Our trimmed test signature, described below, was 659 × 303 px, a ratio of 2.17. In SSC's frame it fills the full height but only about 513 of the 709 px of width, so about 27.6% of the width is white paper. For SSC, a long, low signature fills the frame; for RRB, a more compact one does.

Photograph it flat, in daylight

Hold the phone parallel to the page, directly above it. A tilted phone makes one end of the signature larger than the other.

Take it by a window in daylight. The whitening step can lift a gradual shadow, but a stroke washed out by glare or smeared by a shaking hand is gone before the tool ever sees it.

Fill the frame with paper. Keep the page edge, the table, ruled lines and your fingers out of the picture. Anything the trim step takes for ink widens the crop.

A signature drawn in a signing app and saved as a transparent PNG is laid on white before it is encoded, since a JPEG cannot be transparent.

What the two signature options do

Both are on by default on this page, and either can be switched off.

Trim the empty paper

The tool finds the bounding box of the ink on a small copy of the photo and crops to it, with a 6% margin. Left untrimmed, the paper around the signature would be shrunk into the frame along with the ink, and the signature would sit small in the middle of it.

Make the paper white

A phone photo of white paper is grey, and darker under a shadow. The tool fixes this in two steps.

First it evens out the light: evened = pixel ÷ local paper brightness. The local level is an average over a box reaching about a sixteenth of the photo's longest side in each direction, taken twice so the dark ink does not drag it down. A shadow is only dark paper, so dividing by its own level brings it up to match the rest of the page, while ink stays darker than its surroundings.

Then it splits ink from paper with Otsu's method, which picks the grey level t that maximises the between-class variance σ²(t) = w₀ × w₁ × (μ₀ − μ₁)², where w is each side's share of the pixels and μ its average level. When several neighbouring levels score equally, the tool takes the middle one, so the split does not sit tight against the ink.

The paper becomes pure white. The ink is not made solid black: it keeps its tone in proportion, darkened, so stroke edges stay soft and a pale ballpoint line survives compression to 10 KB. Plain white paper compresses very well, so the file's bytes go to the strokes.

On our test photo

We made a 3,000 × 2,250 phone-style test photo of a signature: grey, unevenly lit paper, a shadow down one side, ink in the middle third. Before the lighting correction existed, the shadowed paper came out dark grey and nothing was trimmed. With it, the paper came out pure white (255), the shadow was gone, and the signature was trimmed to 659 × 303 px. The file was 18,012 bytes against a 20 KB maximum, which the tool counts as 20,000 bytes.

Signature rules on the main forms

As read from the official sources on 24 September 2026, with what each preset produced from our signature test photo. Sizes are written width × height.

Pick your form in the tool's "Form and document" list, and the frame, DPI and byte limits are set for you. For any other form, choose "Another form" and type the limits, a size in pixels or centimetres, and the DPI. Photo, thumb and declaration presets are on the Image Resizer in KB.

Where each notice needs care

SSC

The CGL 2026 notice asks for about 6.0 cm wide by 2.0 cm high; its annexure, and CHSL's, say 4.0 cm wide. The MTS 2025 and GD 2026 notices say 6.0 cm throughout. Every notice shows the upload page, which reads about 6.0 × 2.0 cm at 300 DPI, 10 KB to 20 KB. The preset follows the upload page. The 4.0 cm reading would be 472 px wide at 300 DPI. SSC captures your photograph live in the application, so the photo is not uploaded; only the signature is.

RRB

RRB asks for 30–49 KB, at least 140 × 60 px, scanned at 100 DPI or more. The notice does not say the image must be cropped to the box, but if you crop it that way, 100 DPI is not quite enough: the 35 mm width at exactly 100 DPI is 3.5 ÷ 2.54 × 100 = 138 px, two short of 140. Treat 100 DPI as a floor, not a target. The preset uses 200 DPI, giving 276 × 157 px. RRB also captures the photograph live.

UPSC

The three-signature image must be 20–100 KB, with dimensions of "350 - 500 pixels". UPSC does not say whether that means the width, the height or both, so the preset's 480 × 400 px keeps both sides inside the range.

UPPSC

The guidelines' text says not more than 30 KB; their table says "Less then 30 kb". The two differ only at exactly 30 KB, so the preset stays just under it, at 29,990 bytes or less.

PAN

The two PAN agencies part ways here. Protean's stricter limit for a signature is 10 KB, while UTIITSL's form checks only that the file is no more than 60 KB and has a jpeg, jpg or png extension; the frame reported for UTIITSL comes from third parties. Both agencies' rules, with their sources, are on the PAN Card Photo Resize page.

Why a signature file is often too small

A clean signature is mostly white, and white compresses to very little. IBPS and SBI's 140 × 60 frame is also tiny: 8,400 pixels, about a twentieth of SSC's 1,67,324. In our tests the picture alone came to about 3,100 bytes at that size, about 6,400 bytes for RRB and about 12,700 bytes for UPSC, each below its form's minimum (10, 30 and 20 KB, which the tool reads as 10,240, 30,720 and 20,480 bytes).

So the tool makes up the shortfall with bytes that image viewers skip, and stops at the middle of the form's range, the point furthest from both edges: middle = (minimum KB × 1,024 + maximum KB × 1,000) ÷ 2. For IBPS and SBI that is (10,240 + 20,000) ÷ 2 = 15,120 bytes. The padding adds nothing to the strokes: it makes the file longer, not the signature sharper. Where those bytes sit in a JPEG, and why every viewer ignores them, is covered on the Increase Image Size in KB page.

Common reasons a signature is rejected

Under the minimum. A 6 KB signature sent to a 10–20 KB form. Choose the form's preset or type its minimum.

Over the maximum by the checker's count. A file that Windows calls exactly 20 KB holds 20,480 bytes, too many for a checker that divides by 1,000. Files from this tool stop at X × 1,000 bytes; the 20 KB page shows the arithmetic.

Capital letters. IBPS and SBI state that a signature in capital letters shall not be accepted, however clean the file is.

A signing-app PNG or an iPhone HEIC. SSC and RRB ask for JPG or JPEG, and Protean's table for JPEG. The tool always saves a JPEG, whatever it was given.

Not the signature the form describes. UPSC wants three signatures on one sheet, and SSC wants the signature horizontally aligned. A lone signature falls short of UPSC's rule, and a sloping one of SSC's, whatever the file size.

What this tool assumes

• In a fixed frame the signature is fitted whole with white margins, never cropped, because cropping cuts strokes. Without a fixed size, the trimmed signature keeps its own shape.
• Trimming and whitening are on by default and work by telling dark ink from light paper, so a dark pattern, a ruled line or the page edge can be kept as if it were ink.
• The DPI a preset writes is a label in the file's header; it changes no pixels.
• A maximum of X KB is kept at X × 1,000 bytes or less and a minimum at X × 1,024 bytes or more.
• The signature never leaves your device. The engine's other limits, such as the 30 MB ceiling and the 4,000 px decode cap, are those listed for the Image Resizer in KB.
• A file that meets a form's stated rules can still be refused by its other checks. The tool has no tie to any exam body or PAN agency, and notices change, so check the current one before you upload.