DPI & Print Calculator
Calculate physical print size from pixel dimensions, find required camera resolution for any print size, and evaluate effective print quality.
Calculate DPI & Print Size
Print Inches = Pixels ÷ DPIThe Essential Difference: DPI vs PPI
It is common in design software and colloquial conversation to use DPI and PPI interchangeably, but they describe two distinct physical technologies:
Used exclusively for screens and digital images. Describes how many illuminated electronic pixels exist per inch on a display panel.
Used exclusively for physical printing and scanning. Describes how many microscopic droplets of physical ink a printhead drops per inch.
Print Resolution Formulas
Standard Print Sizes & Pixel Requirements (at 300 DPI)
| Print Size | Dimensions (cm) | Required Pixels (300 DPI) | Megapixels |
|---|---|---|---|
| 4 × 6″ Photo | 10.2 × 15.2 cm | 1200 × 1800 px | 2.2 MP |
| 5 × 7″ Photo | 12.7 × 17.8 cm | 1500 × 2100 px | 3.2 MP |
| 8 × 10″ Portrait | 20.3 × 25.4 cm | 2400 × 3000 px | 7.2 MP |
| 8.5 × 11″ Letter / A4 | 21.6 × 27.9 cm | 2550 × 3300 px | 8.4 MP |
| 11 × 17″ Tabloid Poster | 27.9 × 43.2 cm | 3300 × 5100 px | 16.8 MP |
| 24 × 36″ Large Poster | 61.0 × 91.4 cm | 7200 × 10800 px (at 150 DPI: 3600×5400) | 77.8 MP (19.4 MP @ 150 DPI) |
Frequently Asked Questions
What is DPI and how is it different from PPI?
DPI (Dots Per Inch) measures the physical density of ink droplets that a printer deposits onto paper. PPI (Pixels Per Inch) measures the number of square digital pixels on a digital screen. Digital image files have pixel dimensions (e.g. 3000×2400); dividing those pixels across print inches yields the effective DPI.
What DPI is needed for high-quality photo printing?
300 DPI is the industry standard for professional photo and magazine printing (held 10–12 inches from eyes). 200–240 DPI produces very good quality for wall art and framed prints. For large posters and billboards viewed from several feet away, 100–150 DPI is standard.
How do I calculate print size from pixel dimensions?
Print Width (inches) = Image Width (pixels) ÷ Target DPI. For example, a 3000 × 2400 pixel image printed at 300 DPI will measure 10 × 8 inches (25.4 × 20.3 cm).
How many megapixels do I need to print an 8×10 inch photo?
At 300 DPI, an 8×10 inch print requires (8 × 300) × (10 × 300) = 2400 × 3000 pixels = 7.2 Megapixels. Most modern smartphone and mirrorless cameras (12MP to 48MP) easily exceed this requirement.
Does changing DPI in Photoshop resize the image?
If 'Resample' is turned off in Photoshop, changing the DPI does not add or remove pixels; it simply changes the metadata specifying the physical print size. If 'Resample' is turned on, changing DPI scales and interpolates pixel data.