Pixelcalculator - convert DPI / PPI to pixels and mm, cm, inches
sponsored by: Dia Foto Film Scannen www.archivscan.ch
Formulas for converting DPI - PPI, mm - cm - inches and pixels
|Image:||3266×2449 Pixel (8Mpx, 4:3)|
|Print size:||277 × 207 mm|
With these formulas you can convert the length, pixels and DPI / PPI:
length[mm] = pixel * 25.4mm (1 in) / dpi
pixel = dpi * mm / 25.4 mm (1 in)
dpi = pixel * 25.4 mm (1 in) / mm
Bytes = pixel * color depth / 8 bit (1 Byte)
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 = 300 dpi * 13 mm / 25.4 mm = 1535 pixel
pixel y = 300 dpi * 18 mm / 25.4 mm = 2126 pixel
resolution = 1535 px * 2126 px / 1`000`000 = 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 = 3264 px * 2.54 cm / 100 dpi = 83 cm
width = 2448 px * 2.54 cm / 100 dpi = 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 = 1080 px * 25.4 mm / 24 mm = 1143 dpi
Resulting image size horizontally in the correct aspect ratio:
pixel = 1143 dpi * 36 mm / 25.4 mm = 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 = 4000 dpi * 36 mm / 25.4 mm = 5669 pixel
dpi = 5669 px * 25.4 mm / 900 mm = 160 dpi
|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