Aspect Ratio Calculator
Work out the aspect ratio of any resolution — and what it is commonly called.
What you provide
Result
16:9 — 16:9
1920×1080 reduces to 16:9, which is 16:9. A standard display ratio.
- Aspect ratio
- 16:9
- Decimal
- 1.778
- Orientation
- Landscape
What this cannot tell you
- Pure arithmetic on the dimensions you enter. It does not read your actual screen — type in the resolution you want to check.
- The "21:9" and "32:9" labels are marketing approximations; the true ratios are 64:27 and 32:9. The tool shows both.
Take this with you
How this calculation works
The tool divides the width and height by their greatest common divisor to reduce them to the simplest whole-number ratio, then matches that against the common display ratios. A resolution like 3440×1440 reduces to 43:18 — which the market calls 21:9 — so both the exact ratio and the familiar name are shown.
What the results mean
- Aspect ratio
- The width-to-height relationship in the smallest whole numbers. 1920×1080 reduces to 16:9.
- Common name
- The marketed label. "21:9" ultrawides are really 64:27; "32:9" super-ultrawides really are 32:9.
- Decimal
- The ratio as a single number. Handy for comparing two resolutions quickly — 16:9 is 1.778, 4:3 is 1.333.
Common problems and fixes
- The common-name field is blank
- Your resolution reduces to a ratio that isn't one of the standard marketed shapes, so there is no familiar label to show. 1280×1024, for example, is a true 5:4 — a real ratio, just not a marketing one. The exact ratio is still correct; it simply has no nickname.
- The ratio doesn't match what my screen is advertised as
- Enter the panel's native resolution, not a scaled one. Operating systems often report a scaled resolution (for example a 4K panel running at a 1080p-equivalent scale), and that scaled figure can reduce to a different ratio than the physical panel.
Frequently asked questions
Why is my "21:9" monitor's exact ratio not 21:9?
21:9 is a round marketing figure that covers several slightly different resolutions. 2560×1080 reduces to 64:27 (2.37) and 3440×1440 reduces to 43:18 (2.39) — both close enough to 21:9 (2.33) that the name stuck. This tool shows the exact ratio alongside the marketing name so an unfamiliar-looking number doesn't worry you.
What happens if I play 16:9 content on a 21:9 screen?
It either letterboxes with black bars on the sides, or crops the top and bottom to fill the width — depending on the player. The content was made for a narrower shape, so something has to give.
How do I find the width for a ratio at a fixed height?
Multiply the height by the ratio. For 16:9 at 1440 pixels tall, the width is 1440 × 16 ÷ 9 = 2560, giving 2560×1440. The same works in reverse: divide a width by the ratio to get the matching height.
Put this on your own site
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