Calculate screen PPI, effective print DPI, and the pixel dimensions required for any print size.
Pixel density
√(2560² + 1440²) / 27 ≈ 108.79 PPI
PPI (pixels per inch) for screens is the same math as DPI for prints. Apple calls anything above ~220 PPI "Retina" on laptops and 300+ PPI on phones.
Effective print resolution
Excellent photo quality
min(4000/10, 3000/8) ≈ 300 DPI
The effective DPI is the lower of horizontal and vertical, because the worst axis limits print sharpness. If the image aspect ratio differs from the print, part will be cropped.
Required pixels
8″ × 300 = 2400 px, 10″ × 300 = 3000 px
For sharp photographic prints use 300 DPI. For draft prints or large viewing distances (posters) 150 DPI is usually enough.
Print quality guide
< 72 DPIScreen only — prints look pixelated.
72–150 DPIDraft or newspaper print, large posters at distance.
150–240 DPIGood photo print — acceptable for most home prints.
240–300 DPIExcellent photo quality — standard for magazines.
> 300 DPIMuseum / fine-art quality.
History
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Frequently asked questions
PPI (pixels per inch) describes how many pixels fit in one inch of a digital image or screen. DPI (dots per inch) describes how many ink dots a printer lays down per inch. The math is identical, so in everyday use the terms are interchangeable. This tool labels screen results as PPI and print results as DPI.
At normal viewing distance (about 30 cm) the human eye cannot resolve detail finer than roughly 300 dots per inch. Magazines, photo books and fine prints have used 300 DPI for decades as the "invisible dot" threshold. Going higher rarely helps; going lower starts to show softness or pixel edges.
Same pixels, larger area means lower PPI. A 1080p 24" display has about 92 PPI, while 1080p stretched over 32" drops to roughly 69 PPI. Fewer pixels per inch means text edges and fine details become visibly softer at normal viewing distance.
Retina is Apple's marketing term for a display dense enough that individual pixels are not visible at a typical viewing distance. For phones held about 30 cm away this works out to roughly 300 PPI; for laptops held further back, about 220 PPI; for TVs it drops further because you sit several metres away.
Dot pitch is the distance between adjacent pixels, usually given in millimetres. Smaller is sharper. A 27" 4K monitor has a dot pitch near 0.155 mm; a 24" 1080p display is around 0.277 mm. This tool shows dot pitch under the PPI result in the Screen tab.
You can interpolate pixels with software, but you cannot invent new detail. Upscaling a 1000x1000 photo to print at 300 DPI on 8x10 in will add pixels but still show the original softness. For large prints, either capture at higher resolution or accept a lower effective DPI.
Results are theoretical. Perceived sharpness also depends on viewing distance, paper, ink and software sharpening.
DPI calculator that handles three jobs in one place. Screen mode takes a display’s pixel width, pixel height and diagonal in inches and returns its PPI, dot pitch in millimetres, total megapixels, viewable area and aspect ratio. A preset menu covers phones, tablets, laptops, 1080p, 1440p and 4K monitors, plus common 4K TV sizes. For example a 2560 x 1440 display at 27 inches gives about 109 PPI with a 0.234 mm dot pitch. Print mode converts a source image and a target print size into an effective DPI, with a quality badge ranging from screen-only below 72 DPI to museum quality above 300. A 4000 x 3000 px photo printed at 8 x 10 inches works out to 300 DPI, which is excellent photo quality. Pixels-needed mode reverses the math: enter the print size and target DPI and get the required pixel dimensions. Inputs accept inches, centimetres or millimetres, and a built-in preset list covers 4×6, 5×7, 8×10, letter, tabloid and A6 through A3. Results are clickable to copy, a local history keeps the last ten calculations, and a print quality guide explains each DPI range.