Length

Length

Convert between mm, cm, inches, feet, meters, km, and pixels at any DPI.

🖨️ Screen DPI / PPI Configuration
dots per inch (affects pixel conversions)

Common Presets

📏

Metric

Millimeters mm
25.4
Centimeters cm
2.54
Meters m
0.0254
Kilometers km
0
📐

Imperial & Screen

Inches in
1
Feet ft
0.0833
Pixels px
96

At 96 DPI

Visual Scale (at 96 DPI)

1 inch = 96px
1 cm = 37.7953px
96px
Your value

Quick Reference

1 inch = 25.4 mm
1 inch = 2.54 cm
1 foot = 12 inches
1 meter = 100 cm
1 km = 1000 m
1 inch = 96px (CSS)

Features

  • Convert mm, cm, meters, kilometers
  • Imperial units: inches, feet, yards, miles
  • Pixel conversion with configurable DPI
  • Metric and imperial systems in one tool
  • Precision up to 6 decimal places
  • Quick reference for common conversions

Common Use Cases

  • Convert design mockup measurements to CSS pixels
  • Calculate print dimensions from pixel sizes
  • Convert physical dimensions for 3D printing
  • Understand screen sizes in different units
  • Convert map distances between metric and imperial

Length Measurement Systems

Length measurement uses two primary systems: Metric (meters, centimeters, millimeters) and Imperial (inches, feet, yards). Web design also uses pixels, which vary with screen DPI.

Metric System:

  • Millimeter (mm): 1/1000 of a meter, precision measurements
  • Centimeter (cm): 1/100 of a meter, common for everyday objects
  • Meter (m): Base unit, human scale (height, room dimensions)
  • Kilometer (km): 1000 meters, for distances

Imperial System:

  • Inch (in): 2.54 cm, common for screens and paper
  • Foot (ft): 12 inches, used for height and room dimensions
  • Yard (yd): 3 feet, fabric and sports measurements
  • Mile (mi): 5280 feet, long distances

Pixels and DPI:

  • DPI (Dots Per Inch): Pixel density—higher DPI = more pixels per inch
  • Standard DPI: 96 DPI for web, 72 DPI for older screens, 300 DPI for print
  • CSS pixels: Not physical pixels—1 CSS px ≈ 1/96 inch on standard displays
  • Retina displays: 2× or 3× device pixel ratio (2× CSS px = 4× physical pixels)

Examples

Valid - Screen Size
27-inch monitor = 68.58 cm diagonal
Valid - Print Conversion
300 DPI: 1 inch = 300 pixels
Valid - Physical Distance
1 mile = 1.609 kilometers

Frequently Asked Questions

What DPI should I use for web design?
96 DPI is the web standard. However, modern displays (Retina, HiDPI) have 2× or 3× pixel density. Design at 1× and let CSS handle scaling with device-pixel-ratio.
How do I convert pixels to inches for print?
Divide pixels by DPI. For print, use 300 DPI: 3000px width ÷ 300 DPI = 10 inches wide. For web previews, use 96 DPI: 960px ÷ 96 DPI = 10 inches.
Is 1 CSS pixel always the same size?
No, 1 CSS pixel is a reference unit, not a physical pixel. On Retina displays (2× DPR), 1 CSS pixel = 4 physical pixels (2×2). This ensures consistent visual size across devices.
What's the difference between DPI and PPI?
DPI (Dots Per Inch) is for printers; PPI (Pixels Per Inch) is for screens. Both measure density—higher values mean sharper images. For screens, PPI is technically correct, but DPI is commonly used.
How do I measure screen size from resolution?
You need resolution AND DPI. Example: 1920×1080 at 96 DPI = 20×11.25 inches. Use the Screen/Resolution tool for automatic calculation of physical dimensions from resolution.

💡 Tips

  • For print designs, always use 300 DPI—anything less will look pixelated when printed
  • Web standard is 96 DPI, but design graphics at 2× for Retina displays (192 DPI effective)
  • 1 inch = 2.54 cm exactly—useful for converting design mockups between systems
  • For screen sizes, diagonal measurement is standard: √(width² + height²) in inches

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