DPI Calculator
Calculate DPI, PPI, print size, and pixel dimensions. Convert between resolution, physical size, and pixel count.
Enter values and click Calculate.
How Does the Formula Work?
The DPI calculator converts between three interconnected values in digital imaging: resolution (DPI/PPI), pixel dimensions, and physical print size. DPI stands for Dots Per Inch; how many ink dots a printer places in each inch. PPI stands for Pixels Per Inch; how many pixels a screen displays per inch. Though technically different (DPI refers to print, PPI to screens), the terms are commonly used interchangeably. This calculator operates in three modes: find DPI from pixels and physical size, find pixel dimensions from DPI and physical size, or find print size from pixels and DPI. It supports input in inches, centimeters, and millimeters, and shows results in all three units plus megapixels.
Pixels = DPI × Size (inches)
Size (inches) = Pixels ÷ DPI
1 inch = 2.54 cm = 25.4 mm
Megapixels = (Width × Height) ÷ 1,000,000
Example: 3000×2000px @ 300 DPI = 10×6.67 in = 25.4×16.9 cm
Print Resolution
Adobe's Photoshop documentation calls 300 pixels per inch the industry standard for high-quality prints, especially ones seen up close. Large prints viewed from a distance, such as banners and billboards, can work at less, because fine detail is not visible from far away.
Camera Resolution and Print Size
A camera's pixel count sets the largest print at any given DPI. A 12 MP image (4000×3000 pixels) prints at 300 DPI as 13.33×10 inches (33.9×25.4 cm), a little larger than A4 (29.7×21 cm). A 24 MP image (6000×4000) prints at 300 DPI as 20×13.33 inches (50.8×33.9 cm), larger than A3 (42×29.7 cm). This calculator gives the largest print size for any pixel count at your target DPI, or the pixels you need for a given print size.
DPI for Graphic Design
In design software the pixel count is what ends up on paper. A document set up at 72 DPI and later printed at 300 DPI has only 0.24 of the pixels it needs along each side, so it prints either small or soft. For print work, set the document to 300 DPI at the final print size from the start. This calculator gives the pixel dimensions any print size needs at the DPI you choose.
Scanning Resolution
When you scan a photo or document to print it larger, multiply the output DPI by the enlargement factor. To print a 4×6 inch photo at 8×12 inches (2× enlargement) at 300 DPI, scan it at 600 DPI; the scan then has 2400×3600 pixels, exactly what 8×12 inches needs at 300 DPI.
DPI vs File Size
Higher DPI means more pixels, and more pixels mean larger files. An A4 page at 300 DPI (2480×3508 pixels) holds 26,099,520 bytes uncompressed at 3 bytes per pixel, about 24.9 MiB. The same A4 at 72 DPI (595×842 pixels) is 1,502,970 bytes, about 17 times smaller. JPEG compression reduces file sizes dramatically but introduces quality loss. PNG and uncompressed TIFF keep full quality but produce larger files.
Pixel Dimensions Reference
An A4 page (21 × 29.7 cm) at 300 DPI needs 2480 × 3508 pixels. A 4×6 inch photo at 300 DPI needs 1200 × 1800 pixels. A business card (3.5 × 2 inches) at 300 DPI needs 1050 × 600 pixels. An Instagram post at 1080 × 1080 pixels prints at 300 DPI as only 3.6 × 3.6 inches (9.1 cm square). A 4K monitor image (3840 × 2160) prints at 300 DPI as 12.8 × 7.2 inches (32.5 × 18.3 cm).
Tips & Recommendations
At 300 DPI every inch of print takes 300 pixels, so a 5×7 inch photo needs 1500 × 2100.
On a screen only the pixel size counts; the DPI stored in the file changes nothing there.
Always verify your image has enough pixels for the target print size at 300 DPI.
MP = width × height ÷ 1,000,000. A 12 MP image (4000 × 3000) covers A4 at 300 DPI.
Frequently Asked Questions
What DPI for printing?
For prints seen up close, 300 DPI, the figure Adobe's Photoshop help gives as the industry standard. Large prints viewed from a distance can go lower.
DPI vs PPI?
DPI = printer dots. PPI = screen pixels. Both measure density per inch. Used interchangeably in practice.
How many pixels for A4 at 300 DPI?
2480 × 3508 pixels.
Does DPI matter for images on a website?
Not on its own. Browsers and monitors show an image by its width and height in pixels, so those are what to set; the DPI tag only matters once you print.
Can I increase DPI of an existing image?
Changing DPI metadata doesn't add detail. You need to resize (upscale) which may reduce quality.
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