AnyTool
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How do I resize an image or video while keeping the same aspect ratio?

Type any three of the four numbers into AnyTool Aspect Ratio Calculator — original width, original height and one new dimension — and it instantly solves the fourth so the proportions stay identical. It also shows the simplified ratio (1920×1080 → 16:9), the decimal (1.778) and the 1:x form, plus a live preview drawn to that ratio. Everything is calculated in your browser, so nothing is uploaded.

  • Solves the classic proportion W1:H1 = W2:H2 — leave one field blank and it auto-fills
  • Simplified ratio, decimal, x:1 and 1:x forms shown live
  • 14 presets: 16:9, 9:16, 4:3, 21:9, 1:1, 3:2, 2.39:1, A4, golden ratio and more
  • Live preview box plus pixel and megapixel counts
  • 100% in your browser — no upload, no signup, works offline

What is

Aspect Ratio

An aspect ratio is the proportional relationship between an image or screen’s width and its height, written as two numbers separated by a colon such as 16:9. It is found by dividing both dimensions by their greatest common divisor, so 1920×1080 reduces to 16:9. Resizing while preserving the aspect ratio solves the proportion W1:H1 = W2:H2 for the missing dimension, which prevents stretching or cropping.

Converters

Related terms

16:9ResolutionGreatest Common DivisorResize ImageCinemascope

Frequently Asked Questions

1920×1080 is 16:9, the standard widescreen HD ratio, with a decimal value of about 1.778.

Dividing 1920 and 1080 by their greatest common divisor (120) gives 16:9, the widescreen ratio used by Full HD, YouTube, modern TVs and presentations. As a decimal it is 1920 ÷ 1080 ≈ 1.778, or 1.778:1. 1280×720, 2560×1440 and 3840×2160 are also 16:9.

Multiply the width by 9 and divide by 16. So a 1280-pixel-wide 16:9 frame is 720 pixels tall.

To keep a 16:9 ratio, height = width × 9 ÷ 16. For 1280 px wide that is 1280 × 9 ÷ 16 = 720 px; for 1920 px it is 1080 px. In AnyTool you set the original ratio to 16:9 (or type 16 and 9 as W1 and H1), enter your new width, and the new height is computed automatically.

No. Every calculation runs in your browser, so nothing is sent to a server and it works offline.

AnyTool Aspect Ratio Calculator computes every result locally in JavaScript using a greatest-common-divisor reduction and the cross-multiplication proportion solver. No value is uploaded, there is no tracking, and the page keeps working offline after the first load.

The most common are 16:9 (widescreen), 9:16 (vertical), 1:1 (square), 4:3 (classic) and 3:2 (photography).

16:9 is standard for video, TV and monitors; 9:16 is vertical for Reels, TikTok and Stories; 1:1 is square for social posts; 4:3 is the classic TV and monitor shape; and 3:2 is common in DSLR photography. Cinema uses 1.85:1 and 2.39:1 (Cinemascope), while paper uses √2:1 (ISO 216 / A4) and design often uses the golden ratio ≈ 1.618:1.

Detailed Explanation

Methodology

How the Aspect Ratio Calculator Works

AnyTool Aspect Ratio Calculator performs every calculation in the browser. The simplified ratio comes from dividing both dimensions by their greatest common divisor — so 1920×1080 reduces to 16:9 — with fractional inputs first scaled to integers so ratios like 2.39:1 reduce correctly. Resizing solves the proportion W1:H1 = W2:H2 by cross-multiplication: the missing dimension equals one known dimension times the ratio of the other pair, for example new height = original height × (new width ÷ original width). The least-recently-edited of the four fields is the one computed, so you can leave any single field blank.

  • Simplified ratio via greatest common divisor (GCD)
  • Resize solver uses cross-multiplication of W1:H1 = W2:H2
  • Any one of the four fields can be the auto-computed target
  • Decimal, x:1 and 1:x forms are derived from width ÷ height
  • All arithmetic is client-side JavaScript — no server round-trip
How It Works

Presets, Preview and Resolutions

Fourteen presets cover video (16:9, 2:1), vertical and square social formats (9:16, 1:1), screens (4:3, 21:9, 16:10, 5:4), photography (3:2, 5:3), cinema (1.85:1, 2.39:1) and print (√2:1 ISO 216 paper, the golden ratio ≈ 1.618:1). Choosing a preset seeds the original ratio and recomputes the new dimensions to match. A live preview box is drawn to the current ratio, scaled to fit its frame, alongside the total pixel count and megapixels, and a table lists standard widths (320 to 7680) scaled to the active ratio with rounded heights.

  • Fourteen grouped presets across video, photo, screen, social, cinema and print
  • Selecting a preset recomputes new dimensions to preserve the ratio
  • Live preview box scaled to the exact current ratio
  • Pixel count and megapixels shown for the resolved size
  • Common-resolution table from 320px to 7680px width
Privacy & Security

Privacy and Offline Use

Because all calculation runs in the browser, no dimension is sent to a server, there is no account or tracking, and the page works offline after first load. The converter is built on a small, pure, unit-tested engine (GCD, ratio simplification, the proportion solver and formatting helpers) that keeps the page itself purely presentational, so behaviour is predictable and consistent.

Aspect ratio calculation: in-browser (AnyTool) vs typical online calculators
CapabilityAnyToolTypical online calculators
ProcessingRuns in your browserOften server-side
SolverAny of 4 fields auto-fills (W1:H1 = W2:H2)Usually one fixed output field
Ratio formsSimplified a:b, decimal, x:1 and 1:xOften only a:b
Presets14 grouped (video, photo, cinema, print…)A handful or none
Live previewBox drawn to the exact ratioRarely
Pixel / megapixelsShown for the resolved sizeSeldom
Works offlineYes (PWA)No
Cost / signupFree, no signupOften ad-heavy or gated

AnyTool reduces ratios with a GCD and solves resizes locally, uploading nothing.