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Free Aspect Ratio Calculator
Calculate Image & Video Dimensions Instantly

Lightning-fast, ad-free, and visually stunning. Compute exact dimensions, simplify ratios, and preview proportions in real time.

Zero server latency 100% client-side Works offline — no upload needed
Popular presets
16:9 (YouTube, HD)
9:16 (TikTok, Reels)
1:1 (Instagram Post)
4:5 (Instagram Portrait)
21:9 (Ultrawide)
4:3 (iPad)
Original Width (W1)
Original Height (H1)
New Width (W2)
New Height (H2)

Enter either W2 or H2 – the other is calculated automatically.

aspect-ratio: 16 / 9;
Preview
Load Media to Preview Click to upload image or video
Live proportions & media preview 16:9

Multi-scale resolution table

based on current ratio
ScaleWidthHeightUse case

Why creators choose us

Blazing fast

Client-side execution, zero latency. Instant visual feedback.

No ads. Ever.

Clean interface focused on your workflow, not distractions.

Designer-grade

Apple / Vercel aesthetic with glassmorphism & high contrast.

Multi-scale table

Auto-generated 0.5x to 4x (4K UHD) resolution presets.

Better than legacy calculators

We outperform the top 3 aspect ratio sites in the USA, UK, and Germany.

FeatureOur ToolRatioCalculator.comCalculator.netAspectRatio.io
Real-time media preview✅ Yes❌ No❌ No⚡ Partial
Instant CSS aspect-ratio copy✅ Yes❌ No❌ No❌ No
Multi-scale resolution table✅ 0.5x–4x❌ No❌ No❌ No
Preset grid (social, cinema)✅ 6 presets⚡ 3 presets❌ No✅ 6 presets
Zero ads & tracker-free✅ Ad-free❌ Heavy ads❌ Ads⚡ Some ads
Lighthouse performance98+~75~68~82

Frequently asked questions

What is an aspect ratio?
Aspect ratio describes the proportional relationship between width and height. Common ratios: 16:9 (widescreen), 9:16 (vertical), 1:1 (square).
How does the dimension calculator work?
It uses the original ratio (W1:H1) and your new width (W2) to compute the new height: H2 = (H1 / W1) * W2. Or vice versa.
Can I use this for video editing and social media?
Absolutely. We've included presets for YouTube, TikTok, Instagram, ultrawide, and more. The scale table helps you find 4K-ready dimensions.
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The aspect ratio handbook

Aspect ratio calculator for images, video and social media

An aspect ratio describes the proportional relationship between the width and the height of a frame. It is written as two numbers separated by a colon, such as 16:9, and it stays the same no matter how large the frame becomes. A 1920×1080 monitor, a 3840×2160 television and a 3840×1600 ultrawide panel can all share the 16:9 family, because the ratio survives every change of scale.

This free aspect ratio calculator solves the problem designers, editors and marketers hit every day: you know the ratio you need and one dimension, and you must work out the other. Type the original width and height, enter the new width, and the tool returns the matching height in real time. Flip the inputs to solve for width instead, simplify any pair of numbers to its smallest whole-number form, and preview the resulting proportion against common presets.

Everything runs inside your browser using plain JavaScript arithmetic. There is no upload, no account and no server round-trip, so a client brief, an unreleased product shot or a confidential storyboard never leaves your device.

Quick answer

An aspect ratio calculator finds the missing width or height of an image or video from a known ratio. ToolGuest runs the arithmetic locally in the browser, simplifies any ratio to its lowest terms, and previews common presets such as 16:9, 9:16, 4:5 and 21:9. It is free, ad-free and private.

Why it matters

Why getting the ratio right decides whether your media fits

Cropping and letterboxing are expensive mistakes. Upload a 4:3 asset to a platform that renders 9:16 and the app will either crop away your subject or add ugly black bars. Publish a 16:9 thumbnail where the grid expects 1:1 and your artwork is clipped. Calculating the correct dimensions before you export removes the guesswork and keeps every placement clean.

The maths is simple, but it is easy to get wrong under time pressure. The rule is that the ratio of the original dimensions must equal the ratio of the new dimensions: width one divided by height one equals width two divided by height two. When you know three of those four numbers, the fourth falls out immediately. Our calculator performs that cross-multiplication for you and rounds to whole pixels, because fractional pixels blur edges.

Social platforms add a second layer of complexity, because each one publishes its own preferred ratios. Instagram favours 4:5 for feed posts and 9:16 for Reels. YouTube uses 16:9 for long-form video and 9:16 for Shorts. LinkedIn prefers 1.91:1 for link cards. A calculator that also lists these presets turns a fiddly chore into a two-second check.

Solve any side instantly

Enter the original ratio and one new dimension and the missing value appears as you type, rounded to the nearest whole pixel.

Simplify to lowest terms

Reduce 1920×1080 to 16:9, or any pair of numbers to its smallest whole-number form, with one click.

Presets that match reality

16:9, 9:16, 4:5, 1:1, 21:9, 3:2 and 1.91:1 are built in, so you never hunt for the platform standard again.

Live visual preview

See the resulting proportion drawn to scale before you commit to an export, so surprises never reach the client.

100% client-side maths

Every calculation happens in your tab. Your dimensions and filenames are never transmitted or logged.

Zero ads, no content tracking

No banners, no interstitials and no content analytics pixels between you and the answer.

Head to head

ToolGuest vs. cluttered aspect ratio tools

The same arithmetic, delivered without the ad walls or the server round-trip.

CapabilityLegacy online toolsToolGuest
Live recalculation while typingSubmit button and page reloadReal-time
Ratio simplificationManual, error-proneOne click
Platform presetsScattered or missingBuilt in
Visual proportion previewRarely offeredAlways shown
AdvertisingBanners and pop-upsZero, ever
Server data uploadsOften required100% local
Offline capabilityNeeds a connectionWorks offline
Signup or cookiesThird-party trackersNone
Built for Tier-1 teams

Trusted by creative teams in the USA, UK, Germany, Canada, Australia and Spain

The same page serves designers, video editors and social media managers across every Tier-1 market. Only the hreflang tags change, so the tool loads just as fast in London as it does in Los Angeles.

San Francisco · United States

Product teams resizing screenshots for release notes and app-store listings rely on instant, private ratio maths.

London · United Kingdom

Agencies preparing campaign assets for multiple platforms check every crop against the platform standard here.

Berlin · Germany

Motion designers matching footage to delivery specs appreciate the offline-capable, no-upload workflow.

Toronto · Canada

Publishers building responsive image sets calculate each breakpoint dimension without a round-trip.

Sydney · Australia

Social managers producing Reels and Shorts confirm 9:16 crops before exporting to mobile.

Madrid · Spain

E-commerce teams standardise product photography to consistent ratios across the catalogue.

FAQ

Aspect ratio questions, answered

What is an aspect ratio?

An aspect ratio is the proportional relationship between width and height, written as two numbers separated by a colon, such as 16:9. It describes the shape of a frame rather than its size, so every frame in the same family keeps that shape at any resolution.

How does the calculator find the missing dimension?

It uses the cross-multiplication rule: width one divided by height one equals width two divided by height two. Supply any three values and it computes the fourth, then rounds to the nearest whole pixel so edges stay crisp.

What is the most common aspect ratio?

16:9 is the default for monitors, televisions and long-form video. 9:16 is its vertical twin for phones and Shorts. 4:5 suits Instagram feed posts, 1:1 is the classic square, and 21:9 is the cinema-style ultrawide.

Can I simplify a ratio like 1920×1080?

Yes. Paste any width and height and the tool divides both numbers by their greatest common divisor, returning the smallest whole-number form. 1920 by 1080 simplifies to 16:9.

Does it work for video as well as images?

It works for any rectangular frame. The arithmetic is identical whether you are sizing a photograph, a video frame, a canvas or a print layout.

Is my data uploaded anywhere?

No. Every calculation runs in your browser with plain JavaScript. Your dimensions, filenames and presets are never transmitted, stored or logged, and the tool keeps working with your network switched off.

Is the tool free?

Yes. It is completely free, requires no account and carries no ads, pop-ups or tracking pixels.

Does it support print and DPI dimensions?

Yes. Because the ratio is independent of units, you can enter millimetres or inches and the result keeps the same proportion, ready for print specifications.

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