DPI / PPI Calculator
What is a DPI / PPI Calculator?
Calculate screen Pixel Density (PPI - Pixels Per Inch), total screen Megapixels, and aspect ratio from horizontal/vertical pixel resolution and physical diagonal screen size (inches).
Why Use This Tool?
- Display & Monitor Shopping: Compare pixel sharpness (PPI) between 4K 27-inch monitors vs 1440p 27-inch monitors.
- Mobile & Retina UI Design: Determine if a display qualifies as a Retina High-DPI screen (300+ PPI).
- Graphic Design Printing: Calculate exact print DPI for physical poster printing.
How to Use
- Enter Horizontal Resolution (e.g. `3840`) and Vertical Resolution (e.g. `2160`).
- Enter Physical Screen Diagonal Size in inches (e.g. `27`).
- View calculated PPI, Dot Pitch (mm), total Megapixels, and aspect ratio.
Real Working Example
Input:
Resolution: 3840 x 2160 (4K UHD) | Diagonal Size: 27 Inches
Output Result:
Pixel Density: 163.18 PPI | Total Resolution: 8.29 Megapixels | Dot Pitch: 0.1557 mm
Important Technical Details & Formulas
- Pythagorean Resolution Formula: `PPI = sqrt(width² + height²) / diagonal_inches`.
- Dot Pitch Calculation: Calculates physical distance between adjacent subpixel centers in millimeters.
- Local Memory Execution: Zero network overhead.
Related Measurement & Time Tools
- Aspect Ratio Calculator: Calculate aspect ratios.
- Device Information: Inspect screen specs and DPR.
- Responsive Screen Tester: Test responsive viewports.
Frequently Asked Questions
What is the difference between DPI and PPI?
PPI (Pixels Per Inch) measures digital screen pixel density; DPI (Dots Per Inch) measures physical printer ink dot density.
What PPI is considered a "Retina" high-density display?
Displays viewed at desktop distance (~20 inches) with 160+ PPI or smartphone distance with 300+ PPI are considered Retina.
How is PPI calculated?
PPI = sqrt(horizontal_pixels² + vertical_pixels²) / screen_diagonal_inches.
Is it free?
Yes, 100% free.
What is the main function of DPI / PPI Calculator?
Calculate screen pixel density (PPI/DPI), total screen megapixels, and aspect ratio from resolution and physical diagonal screen size. This calculator computes dpi / ppi values and parameters accurately in your browser.