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Aspect ratio calculator. Lock the shape, solve the size.

Lock any ratio and solve the missing width or height, simplify any width × height to its lowest terms with GCD, and scale with video, screen and social presets — everything computed in your browser, nothing uploaded.

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A free online tool by Digital Heroes
Aspect ratio
Dimensions (pixels)
16 : 9

Ratio locked. Edit width or height and the other follows. Click the lock to free both and read off the ratio instead.

Calculated locally. Nothing is sent anywhere.

Preview
16:9
Presets
Common ratios
Video & screen
Social & photo

Exact ratios, simplified automatically

Enter any width and height and the calculator reduces it to its simplest whole-number ratio using the greatest common divisor — so 1920×1080 reads as 16:9 and 2560×1600 reads as 16:10. Lock the ratio to resize without distortion, or unlock it to discover the ratio of a size you already have. Decimal ratios like 2.39:1 work too. It runs entirely in your browser, free forever.

§ 02 · what you can do

Every dimension question, answered.

Lock any aspect ratio16:9, 4:3, 1:1, 21:9, 2.39:1 and more — then solve the missing width or height instantly.
Simplify with GCDAny width × height pair reduces to its lowest whole-number ratio — 1920×1080 becomes 16:9.
One-click presets720p to 8K and DCI 4K, plus Instagram, YouTube, X, LinkedIn, Pinterest and A4 photo sizes.
Flip landscape ↔ portraitOne tap swaps ratio and dimensions together, so the shape rotates without distortion.
Live shape previewA scaled rectangle shows the exact visual shape of your ratio and updates as you type.
Decimal ratio & megapixelsRead the decimal W÷H value and the total pixel count alongside the simplified ratio.
§ 03 · how to use it

Four steps, no manual.

  1. Enter your ratio in the Ratio width and Ratio height fields, or click a preset chip.
  2. Type a width or height in the Dimensions section — with the lock closed, the other side recalculates automatically.
  3. Click the lock button to unlock, then type any width and height to measure and simplify the ratio of a size you already have.
  4. Use the orientation toggle to flip landscape and portrait, and read the decimal ratio and megapixels in the result panel.
§ 04 · faq

Frequently asked questions.

Is the Aspect Ratio Calculator free?
Yes — completely free for everyone. No sign-up, no account and no usage limits.
Is it private? Is anything uploaded?
No upload, ever. All the math runs in your browser on your own device — the numbers you type never leave your computer.
Does it work offline?
Yes — once the page has loaded, every calculation, preset and preview works without a connection, because all logic runs locally.
What does the lock button do?
Locked, the ratio is fixed: edit width or height and the other side recalculates so the shape never stretches. Unlocked, both sides are independent and the tool measures and simplifies the ratio of whatever size you type.
How does the ratio simplification work?
It uses the greatest common divisor (GCD). Decimal inputs are scaled to whole numbers first, so cinema ratios like 2.39:1 reduce cleanly, and 1920×1080 always reads as 16:9.

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