Aspect Ratio Calculator

Why Aspect Ratio Matters for AI Video

AI video models like Veo, Pika, and Kling generate tighter, more coherent motion when you target the final aspect ratio at generation time — rather than generating wide and cropping. The framing is built into the take.

Common Ratios

• 9:16 (vertical) — TikTok, Instagram Reels, YouTube Shorts
• 16:9 (landscape) — YouTube, X, LinkedIn, Facebook
• 1:1 (square) — Instagram feed, profile
• 4:5 (portrait) — Instagram feed (vertical)
• 21:9 (cinematic) — Anamorphic widescreen, film

Platform-by-platform sizing rules in 2026

Aspect ratios are the easy part; safe zones and platform-specific specs are where most campaigns waste credits. We test every spec quarterly across the Playcut studio, and the rules below are current as of Q2 2026.

• TikTok. 9:16 at 1080×1920 is the canonical ratio. The platform applies a roughly 7% top crop and a 12% bottom crop for the username and caption overlays, so keep faces and product labels at least 100 pixels inside those edges. Duration sweet spot for organic reach: 21-34 seconds. Spark Ads accept up to 60 seconds. Higher bitrate uploads (8-12 Mbps) outperform default-compressed videos on the For You feed.
• Instagram Reels. 9:16 at 1080×1920 again, but the top safe zone is tighter (about 14% reserved for the header) and the bottom safe zone is wider (about 20% for caption and CTA). Reels under 90 seconds get prioritized in feed; Reels above that count as standard video posts with lower distribution. Audio must be licensed or uploaded by you — AI voiceovers count as your own audio.
• YouTube Shorts. 9:16 at 1080×1920, cap 60 seconds. YouTube does not apply persistent UI overlays during full-screen Shorts playback, so the safe zone is forgiving — but if your Short pulls long-form discovery, viewers may watch in a preview window where the top 18% is hidden behind the channel header.
• YouTube long-form. 16:9 at 1920×1080 minimum; 4K (3840×2160) earns higher CPMs and stronger algorithmic placement. Generate at 16:9 — if you ever need a cinematic letterbox, add the bars in post rather than generating at 21:9 and risking bottom-cropping faces in player thumbnails.
• Instagram feed. 1:1 at 1080×1080 is still the safest default for multi-image carousels. 4:5 at 1080×1350 fills more screen on mobile and has been the better-performing ratio for single-image posts since the 2024 algorithm change. Use 4:5 unless your composition strictly needs square framing.
• X (Twitter). 16:9 at 1280×720 minimum, 1920×1080 preferred. X compresses aggressively — generate at higher resolution than you need and let the platform handle the downscale rather than uploading 720p natively.
• LinkedIn. 16:9 at 1920×1080 for landscape, 1:1 at 1080×1080 for feed, 9:16 at 1080×1920 for Stories. LinkedIn's autoplay starts muted, so the first three seconds need to land visually without sound.

How to check the aspect ratio you already have

Switch the tool above to Pixel size → ratio, type your width and height, and it returns the exact ratio, the decimal, and the closest standard ratio. That is the reverse of what most aspect ratio calculators do.

The arithmetic behind it is simple enough to do by hand. Divide both numbers by their greatest common divisor: 1920 and 1080 share 120, so 1920×1080 reduces to 16:9. Divide width by height instead and you get the decimal — 1.778 for 16:9.

Common resolutions and their ratios

Why "21:9" monitors are not 21:9

Ultrawide displays are marketed as 21:9, but the panels are not. A 3440×1440 monitor is exactly 43:18, or 2.389:1. A 2560×1080 one is 64:27, or 2.370:1. True 21:9 would be 2.333:1.

Both sit close to the 2.39:1 anamorphic scope standard, which is why this tool reports that as the nearest named ratio and shows the exact figure alongside it. The marketing name and the arithmetic genuinely disagree, so it gives you both rather than picking one.

It matters when you export. Rendering at a true 21:9 and displaying on a 43:18 panel leaves thin bars or a slight stretch, depending on how the player scales.

Cinematic ratios for narrative work

For a film festival cut, a cinematic-essay piece, or a branded short film, the platform-default ratios stop applying. Scope — 2.39:1 — is the modern anamorphic standard, delivered at 3840×1600 for 4K or 2048×858 for 2K.

Flat, 1.85:1, is the other theatrical standard, mastered at 1920×1037 for HD. Both are wider than 16:9, so both need to be requested at generation rather than cropped in afterwards.

Letterboxing a 16:9 render is possible but wasteful. You pay for every pixel the model generates, and the bars discard roughly a quarter of the frame you just rendered.

Aspect Ratio Calculator FAQ

Which AI video models support which ratios?

Support varies by model and changes with each release, so check the model rather than trusting a list. The ratios a given model accepts on Playcut are listed on the model lineup.

The rule that does hold: generate in the platform's native ratio instead of cropping afterwards. Cropping throws away pixels the model already spent compute on, and it moves your subject off the composition the model framed for.

Should I generate in 4K and downscale, or generate at platform-native resolution?

For paid social and short-form, generate at platform-native resolution (1080×1920 for TikTok/Reels, 1920×1080 for YouTube). Generating at 4K and downscaling costs 3-4× the credits and the additional detail is invisible after platform compression. For long-form YouTube and theatrical work, generate at 4K. For brand-website hero video, generate at 1080p and let the CDN deliver responsively.

What's the right ratio for an in-product demo?

16:9 at 1920×1080. Product demos that live inside a landing-page hero or a YouTube long-form work best in landscape. The exception is a TikTok/Reels demo cut, where 9:16 is required and the screen-recording aspect needs to be re-blocked to vertical anyway (zooming the relevant UI, not just cropping).

What size should social share images and favicons be?

Open Graph share cards are 1200×630 (1.91:1) — the free OG image generator builds one with your title and brand colors directly in the browser. Favicons are square: export 512×512 and let the free favicon generator produce the full 16/32/180/512 icon set from a single source image. Once an image is the right size, the free image compressor shrinks the file so the page stays fast.

How do I keep faces and logos out of the safe-zone crop?

Use the framing slot in the Veo Prompt Builder to specify "subject's face in the upper third, kept above the 1080×1920 platform overlay zone" or equivalent. AI models respect framing instructions in the prompt — but only if you give them the instruction in those words.

Want the full studio?

Playcut handles aspect ratios across Veo 3.1, Seedance 2.0, and the Nano Banana image models natively — pick the ratio per generation. Start your 7-day trial.