US Letter at 150 DPI is 1275 × 1650 pixels

The working

Pixels are inches multiplied by the resolution.

• Width: 8.5 in × 150 = 1,275, which rounds to 1275 pixels.
• Height: 11 in × 150 = 1,650, which rounds to 1650 pixels.

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 1313 × 1688 pixels.

Is your photo big enough?

To fill US Letter at 150 DPI an image needs at least 1275 × 1650 pixels. Cropped to fill the sheet:

• A 12 megapixel phone photo (4000 × 3000) gives 353 DPI: enough.
• A 24 megapixel camera photo (6000 × 4000) gives 471 DPI: enough.
• A 48 megapixel photo (8000 × 6000) gives 706 DPI: enough.

At 150 DPI the pixels of a print blend together from about 22.9 inches (58 cm) away. 150 DPI is a common minimum for posters and large prints seen from a step or two away, and a usual setting for scanning documents that only need to be read.