Video Aspect Ratio Calculator (16:9, 9:16, 4:5 Pixel Dimensions)
Aspect ratio is a shape, not a size: 1280×720 and 3840×2160 are both 16:9. Problems start when you crop between shapes, because moving a 16:9 landscape frame into a 9:16 vertical one discards about eighty-two percent of the horizontal image. Knowing the exact pixel target before shooting is what prevents that loss.
Divisible by 2: yes — safe for H.264 encoding.
| Format | Standard size | Your longest edge scaled | Crop needed from your frame |
|---|---|---|---|
| 16:9 1080p | 1920 × 1080 | 1080 × 608 | 0.1% |
| 16:9 4K | 3840 × 2160 | 1080 × 608 | 0.1% |
| 9:16 Reels | 1080 × 1920 | 608 × 1080 | 68.3% |
| 1:1 square | 1080 × 1080 | 1080 × 1080 | 43.7% |
| 4:5 portrait | 1080 × 1350 | 864 × 1080 | 55.0% |
| 21:9 cinema | 2560 × 1080 | 1080 × 456 | 33.4% |
Why even numbers matter
H.264 and H.265 encode in macroblocks of sixteen pixels and require even dimensions at minimum. Odd numbers such as 1081×607 either fail to encode or get silently padded, which introduces a one-pixel green or black edge visible on some players. Always round to even, ideally to multiples of four.
Safe zones on vertical platforms
A 1080×1920 vertical video is not fully visible on any of the big platforms. Instagram Reels overlays the caption and action buttons over roughly the bottom 320 pixels and the top 220. TikTok reserves about 480 pixels at the bottom on some layouts. Keep text and faces inside the central 1080×1220 region.
Upscaling versus reframing
Scaling a 1080p master to 4K adds no detail — it only adds file size and, on some platforms, a higher-quality encoding ladder. Reframing, by contrast, genuinely changes composition. If you must deliver both landscape and vertical, shoot 4K landscape and crop vertically, which preserves 1080p resolution in the vertical output.
Platform delivery specifications
| Platform | Ratio | Recommended pixels | Max length | Notes |
|---|---|---|---|---|
| YouTube (standard) | 16:9 | 3840 × 2160 | 12 h | 4K improves the encode ladder |
| YouTube Shorts | 9:16 | 1080 × 1920 | 3 min | Square crops get pillarboxed |
| Instagram Reels | 9:16 | 1080 × 1920 | 3 min | Keep text in the middle 60% |
| Instagram feed | 4:5 | 1080 × 1350 | 60 s | Tallest allowed feed ratio |
| TikTok | 9:16 | 1080 × 1920 | 10 min | Heavy UI overlay at the bottom |
| X / Twitter | 16:9 | 1280 × 720 | 2 min 20 s | Autoplay muted |
| 1:1 or 16:9 | 1080 × 1080 | 10 min | Square performs best in feed |
People also ask
What pixel size is 9:16 for Reels and Shorts?
1080 × 1920 is the standard delivery size. Anything taller than 1920 gets downscaled, and anything narrower than 1080 is upscaled with visible softness.
How do I convert 1920×1080 to a vertical crop?
A full-height vertical crop from 1080p landscape is 608 × 1080, which is below platform standard. Shoot or export 4K landscape and crop to 1080 × 1920 instead.
Does aspect ratio affect video quality?
Not directly, but cropping does — every crop discards pixels. Match the shooting ratio to the primary delivery platform and treat other ratios as secondary crops.
Three worked examples
Same engine, three different starting points — useful if you want to see how sensitive the answer is before you type your own numbers in.
Example 1: known dimension 842.4 px, target aspect ratio "16:9"
On the lower / more conservative end. Divisible by 2: no — round to even numbers before export.
Example 2: known dimension 1080 px, target aspect ratio "16:9"
A typical middle-of-the-road setup. Divisible by 2: yes — safe for H.264 encoding.
Example 3: known dimension 1404 px, target aspect ratio "9:16"
On the higher / more demanding end. Divisible by 2: yes — safe for H.264 encoding.
Quick answers about the Aspect Ratio & Pixel Crop
What exactly does the Aspect Ratio & Pixel Crop work out?
Aspect ratio is a shape, not a size: 1280×720 and 3840×2160 are both 16:9. You enter target aspect ratio, lock dimension and known dimension and the result panel updates straight away, so you can compare two or three versions of the same question in a few seconds.
What do I need before I start?
Only 3 fields: target aspect ratio, lock dimension and known dimension. Nothing else is needed and nothing is stored.
How is it calculated — why even numbers matter?
H. The same maths runs inside this page, so hand-checking the result on paper gives you the identical figure.
Why do two calculators give me different answers for aspect Ratio & Pixel Crop?
A 1080×1920 vertical video is not fully visible on any of the big platforms. Different sites pick different assumptions, so always check which method a calculator states before you trust the gap between two numbers.
What does the "Platform delivery specifications" table on this page tell me?
It is the reference range this tool works against — 7 rows from "YouTube (standard)" (16:9) up to "LinkedIn" (1:1 or 16:9). Use it to sanity-check whether the number you just calculated sits where you expected it to.
Which target aspect ratio should I pick?
The dropdown offers 7 choices — 16:9, 9:16, 1:1, 4:5, 21:9, 4:3 and 3:2. Pick the one that matches your real situation rather than the one you would like to be true; target aspect ratio usually moves the final figure more than any other single input, so it is worth running it twice with the option above and below your guess.
Do I have to press a button or reload the page to see the result?
No. Aspect Ratio & Pixel Crop runs completely inside your browser, so the moment you change a value the cards recalculate — there is no submit step, no page reload and no waiting for a server round trip. That also means it keeps working on a weak or intermittent mobile connection.
Is it free, and do you keep what I type?
It is free with no sign-up, no app install and no usage limit. Nothing you enter into Aspect Ratio & Pixel Crop leaves your device — the calculation is JavaScript running locally, so there is no upload of your figures to DrHint or anyone else.
Can I use it on a phone?
Yes — the layout stacks to a single column on small screens and the number fields open the numeric keypad on both Android and iOS. Many people bookmark this page or add it to their home screen and re-open it whenever the question comes up.
Anything to be careful about with the result?
1080 × 1920 is the standard delivery size. Treat the output as a well-grounded estimate for planning, not as a professional, legal or medical decision on its own.
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