Resolution Scale Calculator — Display Scaling & PPI
Enter a source and target resolution to instantly find the horizontal and vertical scale factors, how many more pixels the target has, and the pixel density in PPI if you enter the screen diagonal. Great for game rendering scale, video upscaling, print resolution, and UI design.
Source resolution
px
px
Target resolution
px
px
inches
Target is larger — upscaling required
- 1
Source width
1,920 px - 2
Target width
3,840 px - 3
Horizontal scale factor
3,840 ÷ 1,920 = 2How many target pixels correspond to each source pixel horizontally.
How does this calculator work?
Scale factor = Target dimension ÷ Source dimension. Area scale = (Target width × height) ÷ (Source width × height). PPI = √(W²+H²) ÷ diagonal (inches). A 1080p→4K scale is ×2 horizontally and ×4 in pixel count. Mismatched aspect ratios cause letterboxing or stretching.
Formula
How this is calculated
When you scale a rendered image from one resolution to another, the horizontal scale factor is simply target width ÷ source width, and the vertical factor is target height ÷ source height. If both factors are equal, the image scales uniformly. If they differ, the aspect ratios do not match and the image will be stretched, letterboxed (black bars top/bottom), or pillarboxed (bars left/right) on the target display.
The area scale factor — target pixels ÷ source pixels — tells you how many times more data the target frame contains. Going from 1080p (2.07 M pixels) to 4K UHD (8.29 M pixels) is exactly a ×4 area scale. Games and VR engines often render at a fractional target resolution and upscale — for example, rendering at 1440p and upscaling to 4K gives a scale of ×1.78 horizontally, reducing GPU load significantly.
Pixel density (PPI) measures how many pixels fit in one inch of the display diagonal. Higher PPI means sharper text and images; Apple's "Retina" threshold (where individual pixels are indistinguishable at normal viewing distance) is roughly 200–300 PPI for phones and 100–150 PPI for desktop monitors. To calculate PPI, this tool divides the diagonal pixel count (√(W²+H²)) by the physical diagonal in inches.
Frequently asked questions
Rendering at 150% of the display resolution (scale factor 1.5×, area factor 2.25×) is a common supersampling setting that noticeably improves anti-aliasing with moderate GPU cost. 200% (area ×4) is high-quality but demanding. Rendering below 100% is known as dynamic resolution scaling — used to maintain frame rate under heavy load.
They differ when the source and target have different aspect ratios — for example, 1920×1080 (16:9) and 2560×1080 (21:9). Scaling one to the other horizontally would squash or stretch the image. Most software handles this with letterbox bars or cropping to preserve the source aspect ratio.
At a typical 60 cm (24 inch) viewing distance, about 100 PPI is the limit of human vision resolution. At 30–40 cm (phone distance), 250–300 PPI is the "Retina" threshold. Larger monitors at desk distance appear sharp at 90–110 PPI; 4K 27-inch monitors deliver ~163 PPI, noticeably sharper than 1080p at ~82 PPI.
Also known as
TG we-Calculate Editorial Team. (2026). Resolution Scale Calculator — Display Scaling & PPI [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/resolution-scale-calculator
TG we-Calculate Editorial Team. "Resolution Scale Calculator — Display Scaling & PPI." TG we-Calculate. 2026. https://we-calculate.com/calculator/resolution-scale-calculator.
TG we-Calculate Editorial Team, "Resolution Scale Calculator — Display Scaling & PPI," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/resolution-scale-calculator
@misc{wecalculate_resolution_scale_calculator, title = {Resolution Scale Calculator — Display Scaling & PPI}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/resolution-scale-calculator}}, year = {2026}, note = {TG we-Calculate} }
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