Photo Mosaic Poster: Sizes, DPI & How to Print One That Looks Sharp

What a photo mosaic poster actually is

A photo mosaic poster is a single large print where the main image is built from hundreds or thousands of small tile photos. From across the room, it looks like a regular poster. From up close, every square is a different photo. Posters are the most common print format for mosaics: cheaper than canvas, sharper than metal, and easy to frame.

The challenge is print resolution. A mosaic that looks great at 1080 pixels on a phone screen will look like a blur at 24 inches if the math is wrong. This guide is the math, the sizes, and the print options.

Standard photo mosaic poster sizes

Six poster sizes cover almost every use case:

• 12x18 inches. Desk or small wall. About 200 tiles visible. Good for a single-occasion gift.
• 16x24 inches. The most popular gift size. About 400 tiles. Reads cleanly from across a room.
• 20x30 inches. A statement piece. About 700 tiles. Hangs comfortably above a couch.
• 24x36 inches. The standard large-poster size. 1,000+ tiles. Big enough to walk up to and study.
• 30x40 inches. Wall-art scale. 1,500+ tiles. Common for weddings and 50th anniversary gifts.
• 36x48 inches. Gallery scale. 2,000+ tiles. For event displays and large-format home installations.

DPI: the math that keeps a mosaic sharp

DPI (dots per inch) is the resolution at which a print is rendered. The standard is:

• 300 DPI. The print industry standard. Sharp from any viewing distance. The right target for most mosaics.
• 200 DPI. Acceptable for posters viewed from 4 feet or further. Fine for large display pieces, but individual tiles will not be crisp up close.
• 400 DPI. Premium print quality. Worth it for a 36-inch poster where viewers will stand inches away.

To calculate the pixel size you need, multiply the print dimensions by the DPI. Examples at 300 DPI:

• 12x18 inches → 3,600 x 5,400 pixels
• 16x24 inches → 4,800 x 7,200 pixels
• 24x36 inches → 7,200 x 10,800 pixels
• 36x48 inches → 10,800 x 14,400 pixels

PicTiler exports up to 14,400 pixels on the long edge, which covers every poster size on the list at 300 DPI.

How many tile photos for each poster size

There is no fixed rule, but the bigger the poster the more tiles you want. Recommended minimums:

• 12x18 inches → 200 tiles minimum, 400 ideal
• 16x24 inches → 400 tiles minimum, 600 ideal
• 20x30 inches → 600 tiles minimum, 1,000 ideal
• 24x36 inches → 1,000 tiles minimum, 1,500 ideal
• 30x40 inches → 1,500 tiles minimum, 2,000 ideal
• 36x48 inches → 2,000 tiles minimum, 3,000 ideal

Below the minimum, the same tile will repeat several times across the poster, and the close-up reveal loses its magic.

Where to print a photo mosaic poster

Once your file is exported, three printing routes work reliably:

Online print services

• Shutterfly and Snapfish are the mainstream options. Reliable, mid-range price.
• CanvasChamp and CanvasDiscount offer poster prints at lower prices, with frequent sales.
• Printful and Printify integrate with print-on-demand. Useful if you want to sell a mosaic design.

Local print shops

A local print shop can usually produce a 24x36 inch poster on premium photo paper in 24 hours. Bring the file on a USB stick. Often cheaper than online services for one-off prints.

Office-supply chains

Stores like FedEx Office and Staples print large-format posters same-day for a low price. Quality is good enough for casual gifts, less ideal for archival use.

Mistakes that ruin a mosaic poster print

• Exporting too low resolution. A 2,000-pixel JPEG looks great on a phone and falls apart at 24 inches. Always export at the print size's pixel target.
• Wrong aspect ratio. A 4:3 mosaic exported for a 2:3 poster will get cropped or stretched. Set the poster size before generating, not after.
• Too few tiles for the size. A 24x36 inch poster with 200 tiles shows visible repetition every few inches. Match tile count to print size.
• Wrong colour profile. Most home services expect sRGB. Some commercial printers expect CMYK. Check the printer's spec before exporting.
• Skipping the proof. Order a small 8x10 proof first if you are spending serious money on a 36-inch print. A small proof catches colour and resolution issues before the expensive print.

Final thoughts

A photo mosaic poster is the format that rewards every extra tile. Pick the size that fits the wall, hit the DPI target, gather more photos than the minimum, and order a proof if you are spending real money. The best mosaic posters look like a single image from across the room and like a photo album from up close. The print quality is what makes the second part possible.