DPI Calculator - CM, MM & Inches to Pixels
Convert any physical measurement (centimeters, millimeters, or inches) to exact pixel dimensions at your chosen DPI resolution. Instantly see the results across all standard DPI values - from 72 DPI (web) to 600 DPI (archival quality).
Quick Presets
3.5 × 4.5 cm at 300 DPI =
413 × 531pixels
3.5 × 4.5 cm across all DPI values
| DPI | Width (px) | Height (px) | Total pixels |
|---|---|---|---|
| 72 DPI | 99 | 128 | 12,672 |
| 96 DPI | 132 | 170 | 22,440 |
| 150 DPI | 207 | 266 | 55,062 |
| 200 DPI | 276 | 354 | 97,704 |
| 300 DPIselected | 413 | 531 | 219,303 |
| 600 DPI | 827 | 1063 | 879,101 |
px = (cm × DPI) ÷ 2.54 · px = (mm × DPI) ÷ 25.4 · px = inches × DPIWhen to Use Which DPI
96 DPI - Screen / Web
Standard Windows display. Use when the portal only asks for pixel dimensions and does not mention DPI at all.
200-300 DPI - Exam Portals
Indian government exams (SSC, IBPS, UPSC, Railways). Use 300 DPI for the sharpest result. Most portals accept 200 DPI minimum.
300-600 DPI - Print / Archival
Print labs, passport print shops, and document scanning. 300 DPI is the industry standard. Use 600 DPI only for archival or legal scanning.
How the cm to pixel calculation works
There is no direct conversion between centimeters (a physical measure) and pixels (a digital measure) without knowing the DPI (Dots Per Inch). Since 1 inch equals exactly 2.54 centimeters, the formula is:
Example: Indian Passport Photo (3.5 cm width at 300 DPI)
- 1. Divide DPI by 2.54: 300 ÷ 2.54 ≈ 118.11 pixels per cm
- 2. Multiply by cm: 3.5 x 118.11 = 413.385
- 3. Round to nearest whole pixel: 413 pixels
Common Photo Size Conversions
| Photo Type | Physical Size | At 200 DPI | At 300 DPI |
|---|---|---|---|
| Indian Passport | 3.5 x 4.5 cm | 276 x 354 px | 413 x 531 px |
| US Passport / Visa | 2 x 2 inches | 400 x 400 px | 600 x 600 px |
| UK / Schengen Visa | 35 x 45 mm | 276 x 354 px | 413 x 531 px |
| OCI Card | 50 x 50 mm | 394 x 394 px | 591 x 591 px |
| Canadian Passport | 50 x 70 mm | 394 x 551 px | 591 x 827 px |
| SSC Signature | ~3.5 x 1.5 cm | 276 x 118 px | 413 x 177 px |
Frequently Asked Questions
What is DPI and why does it matter for photos?
DPI stands for Dots Per Inch (sometimes called PPI - Pixels Per Inch for screens). It defines how many pixels fit into one physical inch. Higher DPI means more pixels per inch, resulting in sharper, higher-quality images. Government portals and print labs typically require 200-300 DPI for exam photos and documents.
What is the difference between DPI and PPI?
DPI (Dots Per Inch) technically refers to printing resolution - how many ink dots a printer places per inch. PPI (Pixels Per Inch) refers to screen resolution. In practice, for digital photo sizing, they are used interchangeably. When an exam portal says '300 DPI', they mean the image should have 300 pixels per inch of physical size.
How do I convert cm to pixels?
The formula is: Pixels = (Centimeters x DPI) ÷ 2.54. For example, 3.5 cm at 300 DPI = (3.5 x 300) ÷ 2.54 = 413 pixels. The 2.54 factor converts centimeters to inches (1 inch = 2.54 cm).
How do I convert mm to pixels?
The formula is: Pixels = (Millimeters x DPI) ÷ 25.4. For example, 35 mm at 300 DPI = (35 x 300) ÷ 25.4 = 413 pixels. The 25.4 factor converts millimeters to inches (1 inch = 25.4 mm).
Which DPI should I use for government exam uploads?
Most Indian government portals (SSC, IBPS, UPSC, Railways) require scanning or capturing photos at 200 DPI or 300 DPI. If the notification does not specify, use 300 DPI for the best quality. For US visa applications (DS-160), 300 DPI producing 600x600 pixels is the standard.
Why does my 3.5x4.5 cm photo show different pixel sizes on different sites?
Because different sites assume different DPI values. At 96 DPI (screen standard), 3.5x4.5 cm = 132x170 px. At 300 DPI (print standard), it is 413x531 px. Always check the portal notification for the required DPI before converting.
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