How do I calculate the aspect ratio of an image?

Enter the width and height in the calculator, or load them straight from an image, and the ratio appears instantly, both as a reduced ratio like 16:9 and as a decimal. The aspect ratio is just width divided by height, reduced to its simplest whole-number form.

What does an aspect ratio like 16:9 mean?

It means that for every 16 units of width there are 9 units of height. The actual pixels can be anything, from 1920 × 1080 to 1280 × 720 to 3840 × 2160, as long as they keep that 16-to-9 proportion. The ratio describes the shape, not the size.

How do I resize an image without distorting it?

Keep the aspect ratio constant. Type your original width and height, then enter a new width in the resize box and the matching height is filled automatically, so the image scales in proportion and nothing stretches. Apply those numbers in a resize tool.

What are the most common aspect ratios?

16:9 for video and most screens, 9:16 for vertical phone and Reels content, 4:3 for older photos and many cameras, 1:1 for square social posts, 3:2 for DSLR photography, and 21:9 for ultrawide. The calculator names the common ratio when your dimensions match one.

Can I get the ratio from an image file?

Yes. Use the 'Get ratio from an image' button to read the file's width and height in your browser and fill them in automatically. The image is never uploaded. Only its dimensions are read locally.

Does changing aspect ratio crop or stretch my image?

This calculator only computes numbers; it does not alter pixels. To actually reach a new ratio you either crop to it, which removes part of the image, or accept letterboxing. Stretching to a new ratio distorts the picture and should be avoided. Crop when you need a different shape.

Aspect Ratio Calculator

Aspect ratio calculator

Enter a width and height, or load them from an image, to get the aspect ratio as a clean ratio and a decimal. Then type a new size and the calculator keeps the proportions locked, so you can resize without stretching. Everything runs in your browser.

Width (px)

Height (px)

Or start from a ratio:

Read in your browser, never uploaded.

Aspect ratio

16:9

Common name

16:9

Decimal

1.778

Orientation

Landscape

Resize keeping this ratio

Type a new width or height, and the other side fills to keep 16:9 exactly.

New width (px)

New height (px)

Files never leave your device
Runs in your browser
Free, no signup

How it works

1
Enter or load the size
Type the width and height in pixels, pick a common ratio, or read the dimensions straight from an image, with no upload.
2
Read the ratio
See the reduced ratio like 16:9, its common name, the decimal value, and whether it is landscape, portrait or square.
3
Scale in proportion
Enter a new width or height and the other side fills automatically, keeping the exact ratio for a distortion-free resize.

What the calculator does

Ratio from pixels or an image

Type dimensions or load them from a file. The image is read in your browser to fill the width and height, and is never uploaded.

Proportional resize built in

Lock the ratio and change one dimension; the other is calculated so the image scales without stretching. The numbers feed straight into a resize tool.

Names the common ratios

When your dimensions match 16:9, 4:3, 1:1, 3:2, 9:16 or 21:9, the calculator labels it, so you instantly know the standard shape.

Where this helps

Social

Fitting video and social slots

Confirm a clip or image is 16:9 for YouTube, 9:16 for Reels, or 1:1 for a feed post before you export, so it fills the frame cleanly.

Resize

Resizing without distortion

Get the matching height for a new width (or the reverse) so a resize keeps the picture in proportion instead of squashing it.

Crop

Planning a crop

Compare an image's current ratio to the target shape to see how much you will need to crop to reach it.

Design

Checking a design spec

Verify that assets match the aspect ratio a template or brand guideline requires before they go into a layout.

Tips that help

1
Scale to resize, crop to reshape
Keeping the ratio resizes safely at any size. Reaching a different ratio means cropping or padding. Never stretch to force a new shape.
2
The decimal helps with odd sizes
When dimensions do not reduce to a neat ratio, compare the decimal (width ÷ height) instead. Close decimals are close shapes.
3
Match the slot before exporting
Each platform expects a ratio. Check it here first so the upload is not auto-cropped or letterboxed in ways you did not intend.
4
Start from the highest resolution
Calculate the ratio on your largest original, then scale down. Enlarging a small image to hit a size cannot add detail.

Aspect ratio: reading it, calculating it, and resizing without distortion

Aspect ratio is the shape of an image, the relationship between its width and height, and it governs whether a photo fits a video frame, a social slot, or a print without ugly stretching or unexpected cropping. This guide explains what the ratio means, how it is calculated, how to scale an image while keeping it, and when reaching a new ratio means cropping rather than resizing. The calculator does the arithmetic in your browser.

What aspect ratio actually describes

Aspect ratio is width relative to height, written as two numbers like 16:9 or 4:3. It describes proportion, not size: a 16:9 image can be tiny or huge, but its width is always 16 units for every 9 of height. That is why the same ratio covers 1280 × 720 and 3840 × 2160 alike.

To find it, you reduce the pixel dimensions to their simplest whole-number form by dividing both by their greatest common divisor. 1920 × 1080 divides down by 120 to give 16:9. The calculator does this automatically and also shows the decimal, width ÷ height, which is handy when no neat ratio exists.

Knowing the ratio matters because every display surface expects one. Video is overwhelmingly 16:9, phone-native content is 9:16, square posts are 1:1. Put the wrong ratio into a fixed slot and the platform either crops it or pads it with bars.

Resizing while keeping the ratio

Scaling an image safely means changing its pixel dimensions while holding the ratio constant, so it shrinks or grows without distortion. The maths is a proportion: new height equals new width times original height divided by original width.

The resize box in the calculator does exactly this. Enter your starting dimensions, then type the new width you want and the matching height appears, locked to the same shape. Those are the numbers to enter into a pixel resize tool to apply the change.

This is the difference between resizing and distorting. Resizing keeps the ratio and looks correct at any size; setting width and height independently breaks the ratio and stretches faces and circles. When in doubt, change one dimension and let the ratio decide the other.

When a new ratio means cropping, not scaling

Sometimes you genuinely need a different shape: a 4:3 photo for a 1:1 Instagram tile, or a landscape shot for a 9:16 story. No amount of proportional resizing changes the ratio; only cropping or padding does.

Cropping to the new ratio keeps the pixels sharp but removes part of the frame, so you choose what to lose. That is a job for a crop tool, where you can set the target ratio and position the keep-area by eye.

Stretching to force a new ratio is the option to avoid: it fills the frame but warps everything in it. As a rule, scale to change size, crop to change shape, and never stretch to change ratio.

Frequently asked questions

Honest answers to what people ask before using this tool.

Aspect ratio calculator

How it works

Enter or load the size

Read the ratio

Scale in proportion