📐 Aspect Ratio Calculator
Calculate aspect ratios, simplify ratios, and resize dimensions while preserving the ratio. Built for images, videos, and screens — all in your browser.
Calculate ratio
Resize preserving ratio
About the Aspect Ratio Calculator
This aspect ratio calculator does three jobs at once: it simplifies any width-to-height ratio to its smallest whole-number form (so 1920×1080 becomes 16:9), it shows the decimal ratio and the height-as-a-percentage-of-width, and it resizes dimensions while keeping the same ratio. Type a width and height and every value updates live. All math runs locally in your browser.
How the calculation works
- Simplified ratio — divides both numbers by their greatest common divisor (GCD). For 1920 and 1080, GCD = 120, so the ratio is 16:9.
- Decimal ratio —
width / height(e.g. 1.778 for 16:9). - Height % of width —
height / width × 100(e.g. 56.25%). - Resize by width —
newHeight = newWidth × height / width. - Resize by height —
newWidth = newHeight × width / height.
Common aspect ratios
- 16:9 — Standard widescreen for YouTube, TV, and most monitors.
- 4:3 — Classic TV and older monitors.
- 21:9 — Ultrawide monitors and cinematic film.
- 1:1 — Square images (Instagram posts).
- 9:16 — Vertical video (Stories, Reels, Shorts).
- 3:2 — DSLR and mirrorless camera photos.
How to use
- Enter the original Width and Height.
- Read the simplified ratio, decimal, and percentage below.
- To resize, type a New width to see the matching height, or a New height to see the matching width.
- Use Reset to return to the default 1920×1080.
Frequently asked questions
What if my dimensions are decimals? The calculator rounds to whole numbers for the simplified ratio, since ratios are conventionally expressed with integers. The decimal and percentage values are always exact.
Can I enter a height of zero? No. A height (or width) of zero has no defined ratio and is treated as invalid.
Is my data stored? No. All calculation happens locally in your browser.