Aspect Ratio Calculator
Keep proportions when resizing width & height.
100% private — runs in your browser, nothing is uploaded.
Original size (sets the ratio)
16:91.7778Resize (keeps the same ratio)
How to use the Aspect Ratio Calculator
- 1Enter the original size
Type the width and height that define your ratio, or pick a preset.
- 2Read the ratio
See the simplified ratio (like 16:9) and the decimal value.
- 3Enter a new dimension
Type a new width or height for the resized version.
- 4Get the match
The other dimension fills in automatically, keeping the proportion.
Examples
| Input | Output |
|---|---|
1920 × 1080 | 16:9 (1.7778) |
16:9, new width 1280 | new height 720 |
Free online aspect ratio calculator
This aspect ratio calculator finds the simplified ratio of any width and height, then helps you resize to a new size without distortion. Enter one new dimension and it calculates the other so your image, video or layout keeps its exact proportions.
What aspect ratio means
The aspect ratio is the relationship between width and height, written like 16:9. It stays the same no matter the size: 1920×1080, 1280×720 and 640×360 are all 16:9. Keeping the ratio constant is what stops images from looking stretched or squashed when you scale them.
Common aspect ratios
- 16:9 — widescreen video, monitors, YouTube.
- 4:3 — older screens, some cameras and slides.
- 1:1 — square social posts and profile images.
- 9:16 — vertical Stories, Reels and TikTok.
- 21:9 — ultrawide and cinematic video.
Because it runs in your browser, the calculator is instant, private and works offline.
Frequently Asked Questions
How do I calculate an aspect ratio?
Divide the width and height by their greatest common divisor. For example 1920×1080 both divide by 120, giving 16:9. This tool does it instantly and also shows the decimal ratio.
How do I resize an image without stretching it?
Keep the same ratio. Enter your original width and height, then type the new width — the tool fills in the matching height (or vice versa) so the proportions stay identical and nothing looks squashed.
What is a 16:9 aspect ratio?
16:9 is the widescreen standard used by most monitors, TVs and YouTube videos. It means for every 16 units of width there are 9 of height, so 1920×1080 and 1280×720 are both 16:9.
What aspect ratio should I use for social media?
Common choices are 1:1 (square posts), 4:5 (portrait feed), 9:16 (Stories and Reels) and 16:9 (landscape video). Use the presets to switch between them quickly.
Why are my new dimensions rounded?
Pixel dimensions must be whole numbers, so the calculated side is rounded to the nearest pixel. For exact ratios pick sizes that divide evenly, like doubling or halving.
Is it private?
Yes. Everything is calculated in your browser. Nothing is uploaded, and it works offline.