Pixel Calculator

What this tool does

Pixel Calculator converts between digital pixels and physical measurements (inches, centimeters, millimeters) based on your specified resolution (DPI/PPI). When preparing images for print, you need to know how many pixels are required for a given physical size at your target print quality. Conversely, when you have an image and want to know how large it can print, the calculator determines physical dimensions from pixel counts.

The tool also calculates total megapixels, estimated file sizes for different color depths, aspect ratios, and pixel pitch. This comprehensive information helps photographers, designers, and print professionals make informed decisions about image resolution requirements.

How to use this tool

1. Enter pixel dimensions (width × height) to calculate physical print size, OR enter physical dimensions to calculate required pixels.

2. Set your target DPI/PPI (300 for high-quality print, 72-96 for screens).

3. Select your physical unit preference (inches, centimeters, or millimeters).

4. View calculated results including print size, megapixels, and file size estimates.

5. Optionally upload an image to automatically extract its pixel dimensions.

Common use cases

• Determine print dimensions for a photograph at 300 DPI quality
• Calculate pixels needed for a specific print size (e.g., 8×10 inches at 300 DPI)
• Verify if a camera's resolution supports poster-size prints
• Convert between metric and imperial measurements for print production
• Estimate uncompressed file sizes for storage planning
• Check if an image meets minimum resolution for stock photography submissions
• Calculate optimal dimensions for large format printing
• Determine maximum enlargement size before quality degrades

Key features and behavior

DPI/PPI explained

DPI (dots per inch) and PPI (pixels per inch) are often used interchangeably though technically different. PPI refers to screen/image resolution; DPI refers to print output. For this calculator, both represent how many pixels fit in one linear inch. Standard values: 72 PPI for web, 150 DPI for newspaper, 300 DPI for quality prints, 1200+ DPI for fine art reproduction.

Bidirectional calculation

Enter pixels to get physical dimensions, or enter physical dimensions to get required pixels. You can also enter both to verify DPI. The calculator automatically detects which values you've provided and computes the missing information.

File size estimation

Based on pixel dimensions and color depth, the calculator estimates uncompressed file sizes. 24-bit color (standard) uses 3 bytes per pixel; 32-bit (with alpha) uses 4 bytes. Actual file sizes depend on format and compression—JPEG may be 1/10th of raw size, PNG varies with content.

Template presets

Quick-access presets include standard paper sizes (A4, A3, Letter), photo print sizes (4×6, 5×7, 8×10), film formats (35mm, medium format), and screen resolutions (HD, 4K, 8K). Selecting a preset fills in the corresponding dimensions automatically.

Tips and limitations

• 300 DPI is the standard for quality photo prints; 150 DPI is acceptable for viewing at arm's length
• Large posters viewed from distance can use lower DPI (100-150) since you don't see individual dots
• Monitor "DPI" settings don't affect actual pixel density—they're scaling preferences
• Megapixels = total pixels ÷ 1,000,000, regardless of aspect ratio
• File size estimates are for uncompressed data; actual files are typically smaller
• Upscaling pixels (enlarging) from a smaller source creates soft images regardless of calculation

FAQ

What DPI should I use for printing?

300 DPI is standard for quality photo prints viewed close-up. 150 DPI works for larger prints viewed from a few feet away. Billboards use 20-50 DPI because they're viewed from great distances. Match DPI to viewing distance.

How many megapixels do I need for a large print?

For an 11×14 inch print at 300 DPI: 3300×4200 pixels = ~14 megapixels. For 16×20 at 300 DPI: 4800×6000 = ~29 megapixels. Most modern cameras (12MP+) handle standard print sizes well.

Why are my prints blurry despite having enough pixels?

Pixel count alone doesn't guarantee quality. Motion blur, focus issues, noise, and over-compression also affect sharpness. An out-of-focus 50MP image prints worse than a sharp 12MP image.

What's the difference between DPI and PPI?

PPI (pixels per inch) describes digital image resolution. DPI (dots per inch) describes print output resolution. They're often used interchangeably, but technically a printer may use multiple ink dots to reproduce one image pixel.

Can I change an image's DPI?

DPI is metadata that tells printers how to interpret pixels—it doesn't change actual pixel count. Setting a 1000-pixel image to 300 DPI means it prints at ~3.3 inches. Setting it to 100 DPI means it prints at 10 inches, using the same pixels.

How do I calculate pixels needed for a specific print size?

Multiply physical dimensions by DPI. For 8×10 inches at 300 DPI: 8×300 = 2400 pixels wide, 10×300 = 3000 pixels tall. The calculator does this automatically.

What does the file size estimate represent?

The estimate shows uncompressed file size based on pixel count and color depth. Actual files are smaller due to compression: JPEG at 80% quality might be 10-15% of raw size; PNG varies based on image content.

Why does my camera's megapixel count differ from calculated values?

Camera megapixels measure total sensor pixels. Actual recorded pixels may differ due to rounding, processing, or non-square pixel counts. Minor variations are normal.