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Aspect Ratio Converter

Converter
Mode

Enter Dimensions

Results

16:9

16:9

Simplified Ratio16:9
GCD120
Decimal Ratio1.7778
Percentage Ratio177.78%
OrientationLandscape

1920 : 1080 → GCD(1920, 1080) = 120 → 16:9

Common Aspect Ratio Presets

16:9

16:9

4:3

4:3

3:2

3:2

1:1

1:1

21:9

21:9

9:16

9:16

5:4

5:4

2:1

2:1

3:4

3:4

2:3

2:3

Click a preset to load scaled dimensions for that ratio.

About This Tool

Aspect Ratio Converter – Calculate, Simplify, and Scale Any Ratio

An aspect ratio describes the proportional relationship between a frame's width and its height, expressed as W:H. Whether you are editing a video, cropping a photograph, designing a responsive web layout, or specifying a print bleed area, working with correct aspect ratios prevents stretching, cropping surprises, and black bars. This converter handles four everyday workflows in one place: simplifying any width/height pair into its lowest-terms ratio, solving for a missing dimension given a known one and a target ratio, scaling both dimensions by a factor while preserving the ratio, and comparing two pairs of dimensions to check whether they share the same ratio.

Why Aspect Ratios Matter

Every screen, sensor, and canvas has a native aspect ratio. When you resize content without respecting the ratio, pixels get distorted. A 1920×1080 video frame has a 16:9ratio. Scaling it to 800×450 preserves the ratio; scaling it to 800×600 does not, resulting in a vertically stretched image. The same principle applies when exporting social media graphics (1:1 for square posts, 9:16 for Stories and Reels), when setting width and height attributes on HTML images to avoid layout shift, or when ordering a print at a lab that requires a 4:3 crop from a 3:2 camera sensor.

How the GCD Algorithm Works

The simplification mode uses the Euclidean Greatest Common Divisor (GCD) algorithm. Given width W and height H, it repeatedly computes GCD(W, H) = GCD(H, W mod H) until the remainder is zero. The final non-zero value is the GCD. Dividing both dimensions by the GCD yields the simplest whole-number ratio. For example: GCD(1920, 1080) = 120, so 1920 / 120 = 16 and 1080 / 120 = 9, giving 16:9. If the GCD is 1 — for instance with 1281×721 — the dimensions share no common factor and the ratio is already in its simplest form.

Finding a Missing Dimension

When you know one dimension and a target ratio, the missing dimension follows directly from proportion. The formulas are:

  • Height = Width × (ratio H / ratio W)
  • Width = Height × (ratio W / ratio H)

For example, to find the height of a 1280 px wide frame at 16:9: Height = 1280 × (9 / 16) = 720 px. The tool supports all common presets (16:9, 4:3, 21:9, 1:1, 9:16, 3:2, 5:4, 2:1, 3:4, 2:3) as well as any custom ratio you type in W:H format.

Scaling Dimensions Proportionally

The scale mode multiplies both width and height by a single factor, producing new dimensions that maintain the original ratio exactly. Scaling 800×600 by a factor of 2 gives 1600×1200; scaling the same frame by 0.5 gives 400×300. This is useful when preparing video exports at half resolution for web preview, generating thumbnail variants, or planning DPI-aware print sizes.

Comparing Two Aspect Ratios

It is not always obvious whether two different resolutions share the same ratio. For instance, 1920×1080 and 1280×720 both reduce to 16:9, but 1366×768 reduces to 683:384 — a slightly different ratio despite looking similar. The compare mode simplifies both pairs independently and checks whether the simplified ratios are equal. It also shows the decimal ratio for each pair and the absolute difference, so you can see at a glance how far apart two ratios are even when they do not match exactly.

Common Aspect Ratios and Their Use Cases

  • 16:9 — Standard widescreen: HD and 4K televisions, YouTube, most desktop monitors, smartphone landscape video.
  • 4:3 — Classic television and early computer monitors; still common for PowerPoint slides and tablet screens.
  • 21:9 — Ultrawide cinema (anamorphic). Used in widescreen film and ultrawide gaming monitors.
  • 1:1 — Square format. Instagram feed posts, album artwork, profile photos.
  • 9:16 — Portrait orientation. Instagram Reels, TikTok, YouTube Shorts, smartphone wallpapers.
  • 3:2 — DSLR and mirrorless cameras; 35 mm film. Gives a slightly wider frame than 4:3.
  • 5:4 — Older CRT monitors; some medium-format camera sensors.
  • 2:1 — Panoramic and dual-square format used in some social media crops and banner ads.

Practical Tips

  • When adding images in HTML, always set both width and height attributes to prevent layout shift. Use the simplify mode to find the smallest integer pair for the aspect-ratio CSS property.
  • For print, confirm the ratio before ordering. A 6×4 inch print (3:2) will crop a differently composed shot than a 7×5 inch print (7:5).
  • Video editors: use the "Find Missing Dimension" mode when you need to calculate the correct height for a letterboxed export or a widescreen crop on a 4:3 timeline.
  • Web designers: use "Scale" to verify how a design at 1440 px width looks at 375 px (mobile) by applying a scale factor of 0.26.

Frequently Asked Questions

Is the Aspect Ratio Converter free?

Yes, Aspect Ratio Converter is totally free :)

Can I use the Aspect Ratio Converter offline?

Yes, you can install the webapp as PWA.

Is it safe to use Aspect Ratio Converter?

Yes, any data related to Aspect Ratio Converter only stored in your browser (if storage required). You can simply clear browser cache to clear all the stored data. We do not store any data on server.

How does the Aspect Ratio Converter work?

Enter a width and height, and the tool reduces them to the simplest W:H ratio using the Greatest Common Divisor (GCD) algorithm. You can also enter a known dimension and a target ratio to calculate the missing dimension, scale both dimensions by a factor, or compare two different dimension sets to see whether they share the same ratio.

What is an aspect ratio and why does it matter?

An aspect ratio describes the proportional relationship between a frame's width and its height. It is written as W:H — for example, 16:9 means the width is 16 units for every 9 units of height. Aspect ratios matter because they determine how content fills a screen, print, or canvas. Using the wrong ratio when resizing causes stretching or pillarboxing/letterboxing.

How do I find the height for a given width and aspect ratio?

Use the 'Calculate Missing Dimension' mode. Enter your known width and select or type a target ratio such as 16:9. The tool computes the required height as: Height = Width × (ratio height part / ratio width part). For example, Width = 1280 with ratio 16:9 gives Height = 1280 × (9/16) = 720 px.

What common aspect ratios are supported?

The tool includes presets for 16:9 (widescreen HD), 4:3 (classic TV/monitor), 21:9 (ultrawide cinema), 1:1 (square / Instagram), 9:16 (portrait / mobile video), 3:2 (DSLR photography), 5:4 (older monitors), 2:1 (panoramic), 3:4 (portrait photography), and 2:3. You can also enter any custom ratio in W:H format.

How accurate are the calculations?

All calculations use exact integer arithmetic for the GCD simplification step, and standard floating-point arithmetic for scaling and missing-dimension results. Results are displayed to up to two decimal places. Very large inputs may produce simplified ratios with large numerators if the dimensions share no common factor other than 1.

Can I compare two different dimension sets to check if they share the same ratio?

Yes. Enable the 'Compare Two Ratios' mode, enter two sets of width/height values, and the tool simplifies both using GCD and checks whether the resulting ratios are identical. It also shows the decimal ratio for each pair and the absolute difference, so you can see exactly how far apart they are even when they do not match.