12 × 18 inch poster at 96 DPI is 1152 × 1728 pixels

12 × 18 inch poster (12 × 18 in) at 96 DPI is 1152 × 1728 pixels, which is 2 megapixels.

Portrait1152 × 1728 pixels
Landscape1728 × 1152 pixels
With 0.125 in bleed1176 × 1752 pixels
Megapixels2
Aspect ratio2:3
File size5.7 MB as uncompressed 8-bit RGB; a JPEG or PNG is smaller
Paper size12 × 18 in (304.8 × 457.2 mm)

The working

Pixels are inches multiplied by the resolution.

Bleed is extra image past the trim line, so that a cut that lands slightly off still leaves ink to the edge. Print shops usually ask for 0.125 in on every side of a US size, which makes the file 1176 × 1752 pixels.

Is your photo big enough?

To fill 12 × 18 inch poster at 96 DPI an image needs at least 1152 × 1728 pixels. Cropped to fill the sheet:

At 96 DPI the pixels of a print blend together from about 35.8 inches (91 cm) away. 96 DPI is the reference resolution of Windows and of the web: CSS defines one inch as 96 pixels, so a web page sized in inches or millimetres is laid out at 96 pixels to the inch.

12 × 18 inch poster at other resolutions

ResolutionPixelsWith bleedMegapixelsUncompressed
72 DPI864 × 1296882 × 13141.13.2 MB
96 DPI1152 × 17281176 × 175225.7 MB
100 DPI1200 × 18001225 × 18252.26.2 MB
150 DPI1800 × 27001838 × 27384.914 MB
200 DPI2400 × 36002450 × 36508.625 MB
240 DPI2880 × 43202940 × 43801236 MB
300 DPI3600 × 54003675 × 54751956 MB
400 DPI4800 × 72004900 × 73003599 MB
600 DPI7200 × 108007350 × 1095078222 MB
1200 DPI14400 × 2160014700 × 21900311890 MB

Other sizes at 96 DPI

12 × 18 inches is a small poster with the 2:3 shape of a camera frame, so a photo fills it without cropping. See 12 × 18 inch poster in pixels at every resolution or everything at 96 DPI.