Aspect Ratio Calculator for Images, Video & Screens

Find simplified ratios, missing dimensions, proportional resize sizes, crop or contain results, print measurements and CSS ratio code from one designer-friendly calculator.

1. Source dimensions

Pixels, points or any matching unit

Source width

Source height

Optional: choose, drop or paste a raster imagePNG, JPG, WebP or GIF · dimensions are read locally

2. Target aspect ratio

Keep source or choose a new frame

Ratio preset

Ratio width

Ratio height

3. Output dimension rule

Choose which value controls the result

Calculation mode

Output or maximum width

Output or maximum height

Scale percentage

Rounding rule

Snap to pixel multiple

4. Fit and preview

Compare target frame treatment

Source inside target frame

Contain background colour

Print resolution (PPI)

Rule-of-thirds gridCentre safe area

5. Calculate and export

Finalise the visible result before download

Live preview is automatic. Choose Calculate Results after editing to validate the values and enable matching copy and download actions.

Live ratio preview

Target frame, source treatment and calculation details update while you edit.

16:9 source16:9 target

1280 × 720

1280 × 720Output dimensions

LandscapeOrientation

0.92 MPPixel area

66.67%Width scale

Simplified source ratio

16:9

Decimal 1.7778

Requested target ratio

16:9

Decimal 1.7778

Final output ratio

16:9

Ratio error 0%

Crop or contain result

No adjustment

Source and target ratios match.

Approximate print size

4.27 × 2.40 in

10.84 × 6.10 cm at 300 PPI

Closest common format

16:9 Widescreen

Exact common-ratio match.

aspect-ratio: 16 / 9;

Reference width	Matching height	Dimensions	Megapixels

Default 16:9 calculation is ready. Edit any value or add an image.

Calculate image, video and screen aspect ratios accurately

An aspect ratio describes the proportional relationship between width and height. This calculator reduces dimensions to their simplest ratio, finds a missing width or height, builds equivalent resolutions, compares source and target frames, and explains what happens when content is cropped or contained.

Simplify any width and height

Turn pixel dimensions such as 1920 × 1080, 1080 × 1350 or decimal measurements into a reduced width-to-height ratio and decimal value.

Calculate missing dimensions

Enter a required width, height, maximum box or scale percentage and receive dimensions that preserve the selected ratio.

Preview crop and contain

See whether a target frame removes side or top pixels, or adds unused space around the complete source.

Use creator-ready presets

Choose square, portrait, photography, classic display, widescreen, vertical video, ultrawide, cinematic and paper-oriented ratios.

Build a resize reference table

Generate matching dimensions across common widths for design systems, exports, responsive layouts, video frames and image assets.

Copy CSS and reports

Copy a current aspect-ratio declaration and export the complete calculation as a readable TXT report or CSV table.

How to use the aspect ratio calculator

Follow the same sequence as the calculator interface to determine a ratio and prepare proportional dimensions.

Enter source dimensions or add an imageType the current width and height, or choose a PNG, JPG, WebP or GIF image to read its dimensions automatically in the browser.
Choose the target aspect ratioKeep the source ratio, select a common square, portrait, landscape, video or cinematic preset, or enter a custom width-to-height ratio.
Set the required output sizeCalculate from a known width, known height, maximum bounding box or percentage scale, then choose rounding and pixel-multiple rules.
Review crop, contain and preview resultsCompare the source and target frames, inspect crop or padding estimates, view print dimensions, and check the generated resize table and CSS ratio code.
Calculate, copy or downloadChoose Calculate Results to finalize the current values, then copy the summary or CSS and download a TXT or CSV report.

Aspect ratio formulas for width, height and resizing

Find the ratio

Divide width and height by their greatest common divisor. For 1920 × 1080, the divisor is 120, producing 16:9.

Find height from width

Height = width ÷ ratio decimal. At 16:9, a width of 1280 gives 1280 ÷ 1.7778 ≈ 720.

Find width from height

Width = height × ratio decimal. At 4:5, a height of 1350 gives 1350 × 0.8 = 1080.

Compare ratio error

The final rounded width divided by final rounded height is compared with the requested ratio to reveal any small pixel-rounding difference.

Common aspect ratios and practical uses

Ratio	Orientation	Common use	Example dimensions
1:1	Square	Square posts, thumbnails, avatars and tiles	1080 × 1080
4:5	Portrait	Vertical feed images, posters and product layouts	1080 × 1350
3:2	Landscape	Photography and camera images	1500 × 1000
4:3	Landscape	Classic displays, presentations and older video	1600 × 1200
16:9	Landscape	Widescreen video, slides and modern displays	1920 × 1080
9:16	Portrait	Vertical video and full-height mobile content	1080 × 1920
21:9	Ultrawide	Cinematic banners and ultrawide screens	2560 × 1080
2.39:1	Cinematic	Wide film-style frames and hero artwork	2390 × 1000

Crop versus contain when aspect ratios do not match

Crop to fill the complete frame

The source is enlarged until no empty area remains. A wider source loses pixels from the left and right; a taller source loses pixels from the top and bottom.

Contain the complete source

The entire source remains visible inside the target frame. The calculator reports the approximate horizontal or vertical space left around it.

Use dimensions only for planning

Choose Dimensions only when you need proportional sizes without simulating how an existing image or video would fit inside a different frame.

Protect important content

Enable the rule-of-thirds and centre-safe overlays to plan subject placement before cropping, resizing or exporting in another editor.

Use calculated ratios in responsive CSS layouts

The generated CSS uses a width-to-height ratio, such as aspect-ratio: 16 / 9;. It can define a preferred shape for media wrappers, cards, embeds, thumbnails and responsive components while one dimension remains automatic.

Responsive media wrappers

Set a flexible width and the calculated aspect ratio so the browser derives a proportional height as the layout changes.

Consistent design systems

Use one ratio across card images, video placeholders or content tiles to prevent irregular component heights and layout shifts.

Private browser-based dimension calculation

Optional images remain in the current session

No page-specific upload endpoint receives the selected raster image. It is decoded locally only to read dimensions and show the preview.

No account or database is required

Dimension values, recent calculations and generated reports are handled in the page and are not written to a page-specific database.

Temporary image references are released

The image reference is revoked when the image is removed, the tool is reset or the page is closed.

The calculator does not resize files

Reports contain dimensions and planning information only. They do not include or upload the source image.

Aspect ratio limitations and troubleshooting

A ratio looks unusually large

Decimal measurements can create a detailed integer ratio. Use a common preset or enter a simpler custom ratio when that better represents the intended format.

Rounded dimensions are not exact

Whole pixels cannot always represent a decimal ratio perfectly. Check the displayed ratio error or reduce the pixel-multiple requirement.

An image does not load

The file may be empty, corrupted, mislabeled, unsupported by the browser or too large for available memory. Try a standard PNG, JPG, WebP or GIF copy.

Crop removes important content

Choose Contain, select a closer target ratio, or use the safe-area overlay to plan a less destructive crop in an image editor.

Downloads are unavailable

Choose Calculate Results after the latest edit. This prevents a stale report from being downloaded with older values.

Platform requirements can change

Use presets as practical planning formats and confirm the current upload requirements of the destination service before publishing.

Frequently asked questions about aspect ratios

Answers about simplified ratios, missing dimensions, resizing, cropping, containing, print size, CSS, image detection, reports and mobile use.

What does this aspect ratio calculator do?

It simplifies a width and height into an aspect ratio, calculates a missing dimension, resizes dimensions proportionally, compares source and target ratios, estimates cropping or padding, creates common scale sizes and provides CSS aspect-ratio code.

How is aspect ratio calculated?

Aspect ratio is width divided by height and is normally written as width:height. Integer dimensions are reduced by their greatest common divisor, so 1920 by 1080 simplifies to 16:9.

Can I calculate a missing height from a width?

Yes. Choose Calculate from width, enter the required width and select a target ratio. The matching height is calculated automatically.

Can I calculate a missing width from a height?

Yes. Choose Calculate from height, enter the required height and the calculator returns the proportional width.

Does the calculator accept decimal dimensions or ratios?

Yes. Positive decimal values are accepted and reduced to a practical ratio using up to six decimal places. Output pixel dimensions are rounded according to the selected rule.

What is the difference between 16:9 and 9:16?

16:9 is landscape because the width is greater than the height. 9:16 is portrait because the height is greater than the width. They contain the same numbers in opposite orientation.

What aspect ratio is 1920 by 1080?

1920 by 1080 reduces to 16:9 and has a decimal ratio of approximately 1.7778.

What aspect ratio is 1080 by 1350?

1080 by 1350 reduces to 4:5, a portrait ratio commonly used for vertical image layouts.

What aspect ratio is 1080 by 1920?

1080 by 1920 reduces to 9:16, a full-height vertical video and mobile-screen ratio.

What aspect ratio is 1200 by 630?

1200 by 630 reduces to 40:21 and has a decimal ratio of approximately 1.9048, which is very close to 1.91:1.

Can I upload an image to detect its aspect ratio?

Yes. Add a genuine PNG, JPEG, WebP or GIF image and the browser reads its intrinsic pixel dimensions. The file is used only for local dimension detection and preview.

Does uploading an image change or compress it?

No. The optional image input is only used to read dimensions and show a visual preview. This page does not create a resized image file. Use a related image resizer or converter when an actual edited image is required.

What does crop to fill mean?

Crop to fill enlarges the source until the target frame is completely covered. When the source and target ratios differ, pixels outside the frame are removed from the wider or taller direction.

What does contain complete source mean?

Contain scales the complete source inside the target frame without cropping. When the ratios differ, unused horizontal or vertical space remains around the image.

How are crop pixels calculated?

The calculator finds the largest centered rectangle inside the source that matches the target ratio. It reports the total pixels removed and the estimated amount removed from each opposite edge.

Can I calculate dimensions that fit inside a maximum box?

Yes. Choose Fit within maximum box and enter maximum width and height. The calculator returns the largest target-ratio frame that fits within both limits.

What does snap to a pixel multiple do?

It rounds output dimensions to a selected multiple such as 2, 4, 8 or 16 pixels. This can be useful for video, texture, layout or encoding workflows, although it may create a very small ratio difference.

Can I choose floor, nearest or ceiling rounding?

Yes. Floor keeps calculated dimensions at or below the fractional value, nearest uses standard rounding, and ceiling rounds upward.

What is ratio error?

Ratio error measures the percentage difference between the requested target ratio and the final rounded output dimensions. With one-pixel rounding it is normally extremely small.

Can I calculate print size from pixels?

Yes. Enter a pixels-per-inch value such as 300 PPI. The calculator shows approximate print width and height in inches and centimetres.

Does aspect ratio determine image quality?

No. Aspect ratio describes shape, not detail. Image quality also depends on pixel dimensions, source quality, compression, display size and editing.

Can two different resolutions have the same aspect ratio?

Yes. For example, 1280 by 720, 1920 by 1080 and 3840 by 2160 are all 16:9. They have the same shape but different pixel counts.

What CSS code does the calculator provide?

It creates an aspect-ratio declaration using the selected target ratio, for example aspect-ratio: 16 / 9;. At least one element dimension normally needs to remain automatic for the preferred ratio to affect layout sizing.

Can I copy or download my calculation?

Yes. After calculating, copy the full summary or CSS code, or download a TXT report and CSV scale table. Download filenames begin with correctioncopy.com_.

Does the calculator save my image or dimensions?

No page-specific endpoint receives the optional image or calculation values. The current session holds the preview and recent calculations, and reset clears them.

Does this aspect ratio calculator work on mobile?

Yes. The controls, preview, scale table, copy actions and downloads are responsive for current mobile browsers. File-download behavior can vary by operating system.

Do I need an account or installation?

No page-specific account or installation is required. Enter dimensions in a compatible browser and calculate the results.

Why are downloads disabled after I edit a value?

Changing a source dimension, ratio or output setting makes the previous export stale. Choose Calculate Results again so the downloaded report matches the visible values.

How do I reset the calculator?

Choose Reset Tool to remove the optional image, restore the default 1920 by 1080 example, clear recent calculations and generate a fresh default result.