How this instrument works
A screen's aspect ratio is the simplified proportion of its width to its height, expressed as two whole numbers such as 16:9. It describes shape independently of physical size or pixel count — a 24-inch monitor and a 65-inch TV can share the exact same 16:9 ratio despite being wildly different sizes, because ratio only captures proportion.
Finding that simplified ratio from a raw resolution uses the greatest common divisor (gcd) of the width and height in pixels. Dividing both numbers by their gcd strips out every common factor, leaving the smallest whole-number pair that still describes the same shape — 2560 and 1440 both divide evenly by 160, reducing to 16:9 with nothing left to simplify further.
Standard widescreen monitors and TVs mostly cluster around 16:9, but a growing range of ultrawide and super-ultrawide monitors use ratios like 21:9 or 32:9 for extra horizontal desktop space, while older monitors and some professional displays still use 16:10 or 4:3. Comparing raw resolutions like 2560x1440 versus 3440x1440 hides this difference; comparing their reduced ratios makes the shape difference explicit.
- Enter your monitor or TV's pixel resolution into Width (px) and Height (px) — check the display's specification sheet or your OS display settings if you're unsure.
- Read the simplified ratio from Simplified ratio — width part and Simplified ratio — height part, shown together as width:height.
- Compare the reduced ratio against common screen shapes — 16:9 for standard widescreen, 21:9 or wider for ultrawide, 4:3 for older or specialist monitors.
- Shopping for a new display? Run each candidate's advertised resolution through the instrument to see past marketing size claims and compare actual screen shape directly.
Worked example — a 2560x1440 QHD monitor
Enter 2560 into Width (px) and 1440 into Height (px) — a common QHD (1440p) widescreen monitor resolution. The greatest common divisor of 2560 and 1440 is 160. Dividing both numbers by 160 gives Simplified ratio — width part = 16 and Simplified ratio — height part = 9, so the screen reduces to a 16:9 ratio.
That 16:9 result matches the resolution's reputation as a standard widescreen monitor — same shape as a 1920x1080 Full HD panel, just with more pixels packed into the identical proportions, which is why QHD monitors are marketed as a sharper upgrade rather than a differently shaped one.
Questions
Why do 2560x1440 and 1920x1080 both count as 16:9?
Because aspect ratio only tracks the proportion between width and height, not the absolute pixel count. 2560 divided by 1440, and 1920 divided by 1080, both reduce via their gcd to the same 16:9 ratio — 2560x1440 simply packs more total pixels into that identical shape, which is why it looks sharper at the same physical screen size rather than differently proportioned.
What ratio are ultrawide monitors?
Most common ultrawide monitors use 21:9, and super-ultrawide models stretch to 32:9. A typical ultrawide resolution like 3440x1440 doesn't reduce to a perfectly clean 21:9, though — running it through the gcd calculation gives 43:18, which is extremely close to 21:9 (the small difference comes from the exact pixel counts manufacturers chose) but not an identical reduction.
Is 16:9 the same as 1920x1080?
No — 1920x1080 is one specific resolution that happens to reduce to 16:9; it's not the only one. Any resolution whose width and height share that same simplified 16:9 proportion, including 2560x1440, 3840x2160 (4K UHD) and 1280x720, also counts as 16:9. Aspect ratio and resolution are related but distinct: ratio is shape, resolution is pixel count.
Why do some monitors use 16:10 instead of 16:9?
16:10 gives a taller frame than 16:9 for the same width, which some professional, creative and productivity-focused monitors favour because the extra vertical space suits document editing, spreadsheets and coding better than the wider, shorter 16:9 shape optimised for video. A 16:10 monitor at 1920x1200, for instance, has the same width as a 1920x1080 16:9 monitor but noticeably more height.
How do I use this to compare TVs of different sizes?
Enter each TV's advertised pixel resolution and compare the resulting simplified ratios rather than their diagonal size claims. Two TVs can both be sold as '55-inch' yet differ slightly in shape if one is a legacy or specialist ratio; reducing each to its simplest ratio makes the actual screen proportions directly comparable, independent of the diagonal measurement used in marketing.