Pixelcalculator

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mm ⇒ Pixel

dpi

= Pixel

Pixel ⇒ mm

pix

dpi

= mm

Pixel & mm ⇒ dpi

pix

= dpi

Result

Pixel total	Pixel [ Mpx]
Picture size	mm
dpi / ppi	dpi
Color depth
Disk space	MB
Pitch	μm
Pixel size	μm²

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

Formulas

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

$L e n g t h [m m] = \frac{p i x \times 1 i n [25.4 m m]}{d p i}$

$P i x e l = \frac{d p i \times m m}{1 i n [25.4 m m]}$

$d p i = \frac{p i x \times 1 i n [25.4 m m]}{m m}$

$B y t e s = \frac{}{8 b i t [1 B y t e]} = \frac{(1000 p x \cdot 2000 p x) \times 24}{8 b i t \times 1 M} = 6 M B$

Examples

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).

$P i x e l X = \frac{300 d p i \times 13 m m}{25.4 m m} = 1535 p i x$

$P i x e l Y = \frac{300 d p i \times 18 m m}{25.4 m m} = 2126 p i x$

$R e s o l u t i o n = \frac{1535 \times 2126}{1 ‘ 000 ‘ 000} = 3.3 M p x$

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.

$L e n g t h = \frac{3264 p i x \times 2.54 c m}{100 d p i} = 83 c m$

$W i d t h = \frac{2448 p i x \times 2.54 c m}{100 d p i} = 62 c m$

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.

$d p i = \frac{1080 p i x \times 25.4 m m}{24 m m} = 1143 d p i$

Resulting image size horizontally in the correct aspect ratio:

$p i x e l = \frac{1143 d p i \times 36 m m}{25.4 m m} = 1620 p i x e l$

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.

$P i x e l = \frac{4000 d p i \times 36 m m}{25.4 m m} = 5669 P i x e l$

$d p i = \frac{5669 p i x \times 25.4 m m}{900 m m} = 160 d p i$

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