01 — Ranking
Other free options, ranked
Omni Calculator (Aspect ratio)
omnicalculator.com
4.3Ratio calculator that solves for any missing dimension.
- Best for
- Quick ratio maths with explanations.
- Free plan & limits
- Free with no account. The site shows ads.
Image editors (Photoshop, Photopea, GIMP)
photopea.com
4.4Lock proportions while resizing (the chain icon).
- Best for
- Resizing the actual image file in one step.
- Free plan & limits
- Photopea and GIMP are free, while Photoshop is paid. They resize, but don't tell you the simplified ratio.
Calculator Soup / Digital Rebellion
calculatorsoup.com
4.0Classic online aspect ratio calculators for film and video work.
- Best for
- Video editors who work with anamorphic and cinema formats.
- Free plan & limits
- Free with ads. The interfaces are dated.
CSS aspect-ratio
developer.mozilla.org
4.5A native CSS property: aspect-ratio: 16 / 9.
- Best for
- Web developers keeping responsive boxes, videos and images in proportion.
- Free plan & limits
- Free and supported in every modern browser. It's for layout, not image files.
02 — Comparison
Side by side
Scroll sideways to see every tool. The first column stays pinned.
| Feature / Criterion | This calculator | Omni Calculator | Photopea | Calculator Soup |
|---|---|---|---|---|
| Simplified ratio (e.g. 16:9) | Yes | Yes | No | Yes |
| Resize keeping proportions | Yes (width or height) | Yes | Yes (actual file) | Yes |
| Social and video presets | Yes | Some | No | Some |
| Visual preview | Yes | No | Yes | No |
| Ads | No | Yes | Yes | Yes |
03 — Guide
How to calculate and use aspect ratios step by step
Enter the original width and height
The calculator divides both by their greatest common divisor: 1920 and 1080 share 120, which gives 16:9. Odd sizes such as 1366×768 give awkward ratios (683:384), roughly 16:9.
Enter the size you need
Type the new width (for example 1080) and the height is calculated. If the height is your constraint, type it instead and the width updates.
Use the right ratio for each platform
YouTube: 16:9 (1920×1080). Shorts, Reels and TikTok: 9:16 (1080×1920). Instagram feed: 4:5 portrait (1080×1350) for maximum screen space, or 1:1. Open Graph link previews: about 1.91:1 (1200×630).
Crop rather than stretch
When the ratios don't match, crop the image (see the free image crop tool) or add padding. Stretching distorts faces and text, and platforms will crop the image themselves anyway.
04 — FAQ
Common questions
What aspect ratio is 1920×1080?
16:9. The same ratio applies to 1280×720 (HD), 2560×1440 (QHD) and 3840×2160 (4K UHD).
How do I calculate the height for a given width?
Height = width × (ratio height ÷ ratio width). For 16:9 at 1200 px wide: 1200 × 9 ÷ 16 = 675 px. For 4:5 at 1080 wide: 1080 × 5 ÷ 4 = 1350 px.
What is the best aspect ratio for Instagram?
Portrait 4:5 (1080×1350) takes up the most screen space in the feed. Stories and Reels use 9:16 (1080×1920). Square 1:1 is still supported, and grid previews now show posts cropped to 3:4.
Is this aspect ratio calculator free?
Yes. It's free, has no ads and needs no sign-up. All calculations happen in your browser.
Scores reflect our own assessment of free-tier value. Prices and limits change, so check them on each provider's site before you buy.