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DPI & Pixel Calculator
Convert cm, mm, or inches to pixels — and back — for any DPI.
Know exactly what size to scan your photo for TNPSC, UPSC, APPSC, SSC, and every other exam portal.
Convert Physical Size to Pixels
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Convert Pixels to Physical Size
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Quick Presets — Common Exam Photo Sizes
Exam Photo Size Reference — Pixels, cm, and KB
The table below shows the official photo and signature requirements for every major Indian government exam. Use the calculator above to verify these pixel values against your scanner's DPI.
| Exam | Photo (px) | Photo (cm at 96 DPI) | Photo KB | Signature (px) | Sig KB |
|---|---|---|---|---|---|
| TNPSC | 3.5×4.5 cm (≈ 207×268 @ 150 DPI) | 3.5×4.5 cm | 20–50 KB | 3.5×1.5 cm (≈ 207×89 @ 150 DPI) | 10–30 KB |
| UPSC | 300×350 px (= 7.94×9.26 cm @ 96 DPI) | ~7.9×9.3 cm | max 40 KB | 100×70 px | max 30 KB |
| SSC | 280×340 px (= 7.41×9.00 cm @ 96 DPI) | ~7.4×9.0 cm | 20–100 KB | 140×60 px | 10–30 KB |
| APPSC / TSPSC | 200×230 px (= 5.29×6.09 cm @ 96 DPI) | ~5.3×6.1 cm | 20–50 KB | 140×60 px | 10–30 KB |
| IBPS / SBI | 200×230 px (= 5.29×6.09 cm @ 96 DPI) | ~5.3×6.1 cm | 20–50 KB | 140×60 px | 10–20 KB |
| Railways RRB | 200×230 px (= 5.29×6.09 cm @ 96 DPI) | ~5.3×6.1 cm | 20–50 KB | 140×60 px | 10–30 KB |
| MPSC / KPSC | 200×230 px (= 5.29×6.09 cm @ 96 DPI) | ~5.3×6.1 cm | 20–50 KB | 140×60 px | 10–20 KB |
cm values at 96 DPI (standard screen resolution). Use the calculator above to get pixel counts for your specific scanner DPI.
3.5×4.5 cm to Pixels at Every DPI — TNPSC Photo Size Guide
TNPSC specifies photo dimensions in centimetres, not pixels. The table below converts 3.5×4.5 cm to pixels at every common scanner DPI so you know exactly what setting to use before uploading to tnpscexams.net.
| Scanner DPI | 3.5 cm wide → px | 4.5 cm tall → px | Result | Typical file size |
|---|---|---|---|---|
| 72 DPI | 99 px | 128 px | 99×128 px | ~5–8 KB — too small, low quality |
| 96 DPI | 132 px | 170 px | 132×170 px | ~10–15 KB — may be too small |
| 100 DPI | 138 px | 177 px | 138×177 px | ~12–20 KB — borderline |
| 150 DPI ✓ | 207 px | 268 px | 207×268 px | ~20–35 KB — ideal for TNPSC |
| 200 DPI ✓ | 276 px | 354 px | 276×354 px | ~35–60 KB — good, compress if >50 KB |
| 300 DPI | 413 px | 531 px | 413×531 px | ~80–120 KB — compress before upload |
| 600 DPI | 827 px | 1063 px | 827×1063 px | ~300–500 KB — too large, must compress |
What is DPI? A Plain-Language Guide for Exam Applicants
DPI stands for dots per inch. It describes how many pixels (dots of colour) are packed into every inch of a printed or scanned image. Higher DPI = more detail = larger file size.
When you scan a physical photo with a flatbed scanner, you choose a DPI setting. That setting determines how many pixels the scanner creates per inch of the original. If you scan a 3.5 cm × 4.5 cm photo at 150 DPI, you get:
- Width: 3.5 cm ÷ 2.54 × 150 = 207 pixels
- Height: 4.5 cm ÷ 2.54 × 150 = 268 pixels
The formula is: pixels = (cm ÷ 2.54) × DPI
Reverse: cm = (pixels ÷ DPI) × 2.54
Common DPI values and what they mean
| DPI | Where you see it | Use for exams? |
|---|---|---|
| 72 DPI | Old web standard, Mac screen | No — too low quality |
| 96 DPI | Windows screen default | Barely — file too small |
| 150 DPI | Flatbed scanner, medium quality | Yes — ideal for portal uploads |
| 200 DPI | Good flatbed scan | Yes — compress if over KB limit |
| 300 DPI | Standard photo print quality | Compress heavily before upload |
| 600 DPI | High-resolution scan / archival | Never upload directly — file too large |
Screen DPI vs Scanner DPI — don't confuse them
When you open a photo on your laptop screen, the display DPI (typically 96–160 DPI) determines how large it looks on screen. This is not the same as the scan DPI of the image file. A 200×230 pixel image will look small on a 96 DPI monitor but is perfectly valid for an exam portal that requires exactly 200×230 pixels. The portal only cares about pixel count and file size — not how it looks on your screen.
PPI vs DPI
Strictly speaking, PPI (pixels per inch) is used for screens and digital images, while DPI (dots per inch) is used for printers. In everyday usage — and in government exam notifications — the two terms are used interchangeably. When a scanner app asks for DPI, it means PPI of the output image file.
How to Prepare Your Photo for TNPSC / Government Exam Portals — Step by Step
- 1
Check the official notification for the exact requirement
TNPSC specifies 3.5×4.5 cm and 20–50 KB. Most other exams specify pixel dimensions directly. Note both the size and the KB limit.
- 2
Use this calculator to find the target pixel dimensions
Enter 3.5 × 4.5 cm at 150 DPI → 207×268 pixels. This is your target size for TNPSC.
- 3
Resize to exact pixel dimensions
Use the Photo Resizer — enter the target width and height in pixels, upload your photo, and download the resized file.
- 4
Compress to fit the KB limit
If the file is still above 50 KB, use the Image Compressor to bring it within the limit without visible quality loss.
- 5
Verify before uploading
Right-click the file → Properties → check dimensions and size. Confirm it matches the notification requirement before uploading to the portal.
Also check your age eligibility
Got your photo ready? Now verify you meet the age limit for your target exam — with OBC, SC/ST, and PH relaxation built in.
Frequently Asked Questions
What is 3.5×4.5 cm in pixels for TNPSC? ▾
3.5×4.5 cm at 100 DPI = 138×177 pixels. At 150 DPI = 207×268 pixels. At 200 DPI = 276×354 pixels. TNPSC accepts photos in the range of 20–50 KB in JPEG format. Most candidates scan at 150–200 DPI to get a file in that size range. Use the calculator above to find the exact pixel dimensions for your scanner's DPI setting.
What DPI should I use to scan my photo for government exams? ▾
For government exam photos that specify pixel dimensions (like UPSC 300×350px or APPSC 200×230px), scan at 150–200 DPI and then resize to the exact pixel requirement. For exams that specify cm dimensions (like TNPSC 3.5×4.5cm), scan at 150 DPI — this gives a file around 20–50 KB without extra compression. Avoid scanning above 300 DPI for portal uploads as it creates large files that are hard to compress to the KB limit.
How do I convert pixels to cm for a government exam photo? ▾
Use the formula: cm = (pixels ÷ DPI) × 2.54. For example, 200 pixels at 96 DPI = (200 ÷ 96) × 2.54 = 5.29 cm. At 200 DPI, 200 pixels = (200 ÷ 200) × 2.54 = 2.54 cm. The DPI of your device matters — most computer screens are 96 DPI, photo printers are 300 DPI, and mobile phone screens range from 150 to 460 DPI.
What is the pixel size of a passport photo (3.5×4.5 cm) at different DPI values? ▾
3.5×4.5 cm passport photo pixels: at 72 DPI = 99×128px, at 96 DPI = 132×170px, at 100 DPI = 138×177px, at 150 DPI = 207×268px, at 200 DPI = 276×354px, at 300 DPI = 413×531px, at 600 DPI = 827×1063px. TNPSC and most state PSCs accept this size. Upload after resizing to fit the portal's KB limit (usually 20–50 KB).
What is 2×2 inch passport photo in pixels? ▾
A 2×2 inch US passport photo at common DPI values: at 72 DPI = 144×144px, at 96 DPI = 192×192px, at 150 DPI = 300×300px, at 200 DPI = 400×400px, at 300 DPI = 600×600px. For Indian government exams, IBPS and SBI require a left thumb impression of 240×240px — this is close to the 2×2 inch at 120 DPI.
Why does my photo look blurry after resizing to the portal's pixel requirement? ▾
Blurriness happens when you enlarge a small photo to a larger pixel size — the software interpolates (guesses) missing pixels. Always start with a high-resolution photo (300 DPI or higher) and downscale to the required pixel dimensions. Never upscale a low-resolution photo. For best results: take or scan at the highest quality, then use the PrepTools Photo Resizer to downscale to the exact pixel size needed by the exam portal.