Aspect Ratio Calculator
Set a ratio, type the size you need, and the missing width or height fills in instantly — with preset chips and common resolutions for 16:9, 9:16, 4:3, 3:2, 1:1, 4:5, 21:9 and 2.39:1.
Ratio solver
Preset ratios
Ratio identifier
16:9 — widescreen video (YouTube, HD/4K)
Common sizes for this ratio
- HD (720p)1280 × 720
- Full HD (1080p)1920 × 1080
- QHD (1440p)2560 × 1440
- 4K UHD3840 × 2160
Everything runs locally in your browser. Nothing is uploaded to any server — close the tab and your files are gone.
How to use
Set your ratio
Type W1 and H1 — your original size, or a plain ratio like 16 and 9 — or click a preset chip below to fill them in.
Type the size you need
Fill in W2 or H2. The other one recalculates instantly to keep the exact same ratio as W1:H1.
Check the identifier
The simplified ratio and closest standard name update live, so you can confirm exactly what ratio you’re working with.
Copy and go
Copy W2 × H2 for the new size, or grab any row from the common sizes table once a standard ratio is detected.
Frequently asked questions
How do I resize an image without distorting it?
Keep width and height in the same ratio as the original — stretching either one on its own is what causes distortion. Enter your original size as W1:H1, then type your target width or height into W2 or H2; the other value locks to the same ratio automatically, so nothing gets stretched or squashed.
What is 16:9 used for?
16:9 is the standard widescreen ratio for YouTube, most monitors and TVs, and HD/4K video — 1280×720, 1920×1080 and 3840×2160 are all 16:9. It’s the default for horizontal video on nearly every platform.
What’s the difference between 9:16, 4:5 and 1:1 on Instagram?
9:16 is full-screen vertical video for Reels and Stories (1080×1920). 4:5 is the tallest ratio the main feed displays without cropping (1080×1350). 1:1 is a square feed post (1080×1080). Anything taller than 4:5 gets cropped down when it’s published to the feed.
Why is 1080×1350 the tallest size for an Instagram feed post?
Instagram caps feed posts at a 4:5 ratio — anything taller is cropped down to 4:5 on publish. 1080×1350 is the largest vertical canvas that shows in full without any cropping.
Why doesn’t my exact pixel size match a standard ratio perfectly?
Real export sizes are always whole pixels, so dividing by odd numbers rarely lands on a perfectly clean fraction. This calculator treats anything within about 1% of a standard ratio as a match — for example, 2560×1080 monitors are commonly sold as “21:9” even though the exact fraction is closer to 64:27 — and shows the plain simplified ratio alongside it so you can see both.
What is 2.39:1 and where is it used?
2.39:1 is the anamorphic widescreen ratio used for cinema releases — noticeably wider than the 16:9 you’d see on a TV or monitor. It’s common in film exports and cinematic-style video trailers.