Photo size is in the form of nR where n represents the shorter side of the photo and n is in inches. Eg, 4R size is 4 inches by 6 inches. For 10 inches and below, the longer side is 2 inches longer than the shorter side For 11 inches and above, the longer side is 3 inches longer than the shorter side.

A. Small Prints (Snapshots & Casual Use)
Sizes: 2 × 2 inches (Passport photos); 3.5 × 5 inches (Standard snapshot); 4 × 6 inches (Most common photo print).
Resolution: 300 DPI (600 × 900 pixels for 2×3").
Best For: Wallet-sized photos; Quick prints (drugstores, kiosks); Scrapbooking, DIY projects..
B. Medium Prints (Framing & Display).
Sizes: 5 × 7 inches (Common for portraits); 8 × 10 inches (Popular for framing); 8.5 × 11 inches (Letter size, photo books).
Resolution: 300 DPI (2400 × 3000 pixels for 8×10").
Best For: Home/office photo frames; Greeting cards, invitations; Small posters or art prints.
C. Large Prints (Wall Art & Professional Use).
Sizes: 11 × 14 inches (Gallery-style prints); 16 × 20 inches (Poster size); 18 × 24 inches (Large posters, canvas).
Resolution: 300 DPI (4800 × 6000 pixels for 16×20").
Best For: Wall decor (homes, offices); Wedding/event photography; Fine art prints.
D. Extra-Large Prints (Commercial & Decorative).
Sizes: 20 × 30 inches (Poster, canvas wrap); 24 × 36 inches (Movie poster size); 30 × 40 inches+ (Billboards, murals).
Resolution: 150–300 DPI (varies by viewing distance).
Best For: Trade show banners; Store/wall murals; Museum/gallery exhibitions.

Square Prints (1:1 Ratio): 6 × 6 inches (Instagram-style prints); 12 × 12 inches (Scrapbook/album layouts).
Panoramic Prints (Wide Aspect Ratios): 4 × 12 inches (Landscape panoramas); 8 × 24 inches (Scenic wall art).

① DPI (Dots Per Inch).
300 DPI: Standard for high-quality prints (viewed up close).
150 DPI: Acceptable for large posters (viewed from a distance).
72 DPI: Only suitable for digital screens, not printing.
②. Aspect Ratio.
Match the camera’s ratio (e.g., 3:2 for DSLRs, 4:3 for smartphones).
Cropping may be needed for non-standard sizes (e.g., 8×10 from a 4×6).
③. File Format.
JPEG: Best for most photo prints (compressed but high quality).
TIFF/PNG: Lossless formats for professional editing/printing.
RAW: Used for advanced editing before conversion.

Print Size: 2 × 3" – 4 × 6". Best Use Case: Snapshots, albums, ID photos.
Print Size: 5 × 7" – 8 × 10". Best Use Case: Framed portraits, certificates, gifts.
Print Size: 11 × 14" – 16 × 20". Best Use Case: Wall art, wedding photos, exhibitions.
Print Size: 20 × 30"+ . Best Use Case: Posters, banners, large-scale decor.

Check Printer Resolution: Ensure the image has enough pixels (e.g., 8×10" needs 2400×3000px at 300 DPI).
Use Soft Proofing: Adjust colors for the printer’s color profile (CMYK vs. RGB).
Test Print: Print a small version before large-scale production.
By selecting the right print size and resolution, you ensure sharp, professional-quality photos for any purpose—from personal keepsakes to commercial displays.