# Pixelcalculator - convert DPI / PPI to pixels and mm, cm, inches

The file remains on your device.

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## Result

Pixel total Pixel [ Mpx] 1 Bit - Monochrome 4 Bit - EGA graphics cards 6 Bit - Amiga computer 8 Bit - MSX2 computer 12 Bit - NeXT workstations 15 Bit - Real Color 16 Bit - High color 24 Bit - True color 30 Bit - PAL, HDR video 36 Bit - HDR10 +, Dolby Vision 42 Bit - Flat screen TV 48 Bit - Flatbed scanner MB μm μm²

sponsored by: Dia Foto Film Scannen www.archivscan.ch

## Formulas for converting DPI - PPI, mm - cm - inches and pixels

Calculation of length or width, pixels and DPI with the following specifications:

 Image: 3266×2449 Pixel (8Mpx, 4:3) Print size: 277 × 207 mm Pixel density: 300dpi

With these formulas you can convert the length, pixels and DPI / PPI:

$$Length[mm] = {pix × 1 in [25.4mm] \over dpi}$$

$$Pixel = {dpi × mm \over 1 in [25.4mm]}$$

$$dpi = {pix × 1 in [25.4mm] \over mm}$$

$$Bytes = { \over 8 bit [1 Byte]} = {(1000px · 2000px) × 24 \over 8 bit × 1M} = 6MB$$

## Examples: print resolution, scan resolution and image size in practice

### I want to print a picture for the photo album, 13 x 18 cm, with good quality. How big does the resolution have to be in pixels?

A good quality picture for a photo album is printed at 300 dpi. To calculate the resolution in megapixels, multiply the number of pixels of length and width and divide them by mega (1 million).

$$Pixel X = {300dpi × 13mm \over 25.4mm} = 1535 pix$$

$$Pixel Y = {300dpi × 18mm \over 25.4mm} = 2126 pix$$

$$Resolution = {1535 × 2126 \over 1000000} = 3.3 Mpx$$

### I have an image with 3264 x 2448 pixels and would like to print it as a poster. How big can I print the poster?

In contrast to a small picture in the photo album, the poster does not have to have a high pixel density, as this is viewed from a greater distance and the pixels become smaller for the eye. Approx. 100 dpi is recommended for a poster.

$$Length = {3264pix × 2.54cm \over 100dpi} = 83 cm$$

$$Width = {2448pix × 2.54cm \over 100dpi} = 62 cm$$

### I would like to scan slides and present them with a slide show on the television. Screen TV 40 inches; Resolution: 1,920 x 1,080 pixels. How big does the scan resolution have to be?

The dimensions of a slide are 36 x 24 mm, so the aspect ratio does not match that of the television (television = 16: 9 slide = 3: 2). We only calculate the pixel density of the height of the image, as this is the limiting measure.

$$dpi = {1080pix × 25.4mm \over 24mm} = 1143 dpi$$

Resulting image size horizontally in the correct aspect ratio:

$$pixel = {1143dpi × 36mm \over 25.4mm} = 1620 pixel$$

### I would like to print a poster of 900 x 600 mm with the maximum resolution from a slide. How good will the quality be in "dpi"?

The maximum resolution of the scanner is 4000dpi, a slide has the dimensions of 36 x 24 mm. After you have calculated the number of pixels, you can use the dimensions of the poster to calculate the pixel density.

$$Pixel = {4000dpi × 36mm \over 25.4mm} = 5669 Pixel$$

$$dpi = {5669pix × 25.4mm \over 900mm} = 160 dpi$$

## Units

 engl. unit of length 1 Inch = 25.4 mm dots per inch 1 dpi = 1 Dot per Inche(25.4 mm) pixel per inch 1 ppi = 1 Pixel per Inch(25.4 mm) digital unit of measurement B = Byte 1 bit = 0 | 1 1 B = 8 bit 1 kB = 1024 B 1 MB = 1024 kB