Pixels Per Inch

The Pixels Per Inch calculator compute the pixels per inch based on the diagonal resolution and the diagonal length of a screen.

INSTRUCTIONS: Choose units and enter the following:

• (d_p) This is the diagonal resolution in pixels
• (d_i) This is the diagonal length

Pixels Per Inch (PPI):  The calculator returns the number of pixel density.

The Math / Science

Pixels per inch  is a measurement of the pixel density (resolution) of an electronic image device, such as a computer monitor or television display, or image digitizing device such as a camera or image scanner. Horizontal and vertical density are usually the same, as most devices have square pixels, but differ on devices that have non-square pixels. 

The formula for pixels per inch is: 

      `PPI=d_p/d_i`

where:

• PPI = pixels per inch
• d_p = diagonal resolution in pixels (to calculate: )
• d_i =  diagonal size in inches

Optics and Imagery Calculators

• Snell's Law               `(sin theta_t)/(sin theta_i) = v_2 / v_1 = n_1/n_2` 
  • (θ_i) Angle of Transmission
  • (θ_t) Angle of Incidence
  • (n₁) Refractive Index of Medium 1
  • (n₂) Refractive Index of Medium 2
  • (θ_c) Critical Angle: Uses Snell's law to compute the critical angle based on the Refraction Indices between two mediums.
• Lens Maker's Equation         `f = [(n_"lens"/n_"medium" - 1)(1/r_1 - 1/r_2)]^-1`
  • (f) focal length of the lens
  • (n_lens) Index of refraction of lens
  • (n_medium) Index of refraction of the material surrounding lens.
  • (r₁) Radius of lens curvature of the side nearest the "object" ( the source of the light rays).
  • (r₂) Radius of lens curvature of the side farthest from the object
• Resolving Power of a Telescope    `α = 2.06 x 10^5 ( λ / D )`
• Magnification of a Telescope          `M = F_p "/" F_e`
• Diagonal Pixel Resolution
• Pixels Per Inch
• Real Image from Converging Mirror

References

• Wikipedia (https://en.wikipedia.org/wiki/Pixel_density)