Aspect Ratio Calculator

Aspect ratio is the relationship between the width and height of an image, video, or screen, written as two numbers separated by a colon, such as 16:9 or 4:3. 3. The calculator on this page finds that ratio from any two known values or works out a missing width or height once a ratio is set, so you get a clean result without doing the division by hand.

What Is Aspect Ratio?

Aspect ratio describes shape, not size. It is written as width to height, for example, 16:9, which means 16 units wide for every 9 units tall. A 16 cm by 9 cm photo and a 32 cm by 18 cm photo are both 16:9, because the relationship between the two numbers stays the same even though the actual measurements are different. That is why a ratio on its own never tells you how big something is, only how it is shaped.

How Do You Calculate Aspect Ratio?

There are two ways to express an aspect ratio once you know the width and height: a decimal and a whole number.

For the decimal version, divide width by height. A screen that is 1920 pixels wide and 1080 pixels tall gives 1920 divided by 1080, which comes out to 1.777, usually rounded to 1.78:1.

For the whole number version, find the greatest common factor of the width and height, then divide both numbers by it. The greatest common factor of 1920 and 1080 is 120. Divide 1920 by 120, and the result is 16. Divide 1080 by 120, and the result is 9. So the same screen is also written as 16:9.

Both answers describe the exact same shape. 16:9, 1.78:1, and 1.7:1 are just three ways of writing it, and recognizing all three keeps a different tool's output from throwing you off.

How Do You Find the Greatest Common Factor for a Ratio?

Finding the greatest common factor takes three steps. Write down the width and height. Find the largest number that divides both of them evenly. Divide both numbers by that factor to get the reduced ratio.

Using 1920 and 1080 again, the greatest common factor is 120, which reduces the pair down to 16 and 9. Some tools call this number the GCD instead of the GCF; "greatest common divisor" and "greatest common factor" mean exactly the same thing.

If you need this same calculation for numbers that have nothing to do with images or screens, say simplifying a fraction for a homework problem, the GCF Calculator does the same job on any two numbers.

How Do You Use This Aspect Ratio Calculator?

Using the calculator takes three steps. Pick a preset ratio such as 16:9, 4:3, 1:1, 9:16, 21:9, 3:2, 5:4, 2:1, or 32:9, or type in a custom ratio if yours is not on the list. Enter either the width or the height you are working with. The calculator fills in the matching dimension right away, so there is no manual math to check.

How Do You Resize an Image Without Distorting It?

Resizing without stretching or squishing an image comes down to one formula: original height divided by original width, multiplied by the new width, equals the new height.

Say you have a photo that is 1600 by 1200 pixels, and it needs to fit a space that is only 400 pixels wide. Divide 1200 by 1600 to get 0.75, then multiply that by 400. The result is 300, so the resized photo should be 400 by 300 to keep the same shape.

This is the calculation that keeps a resized image looking normal instead of stretched. Change only one dimension and leave the other alone, and the proportions break.

How Do You Know If an Image Is Portrait or Landscape?

Orientation comes straight from comparing width and height. If the width is bigger than the height, the image is landscape. If the height is bigger, it is a portrait. If both numbers are equal, it is square, neither landscape nor portrait. The calculator above works this out automatically once you enter your dimensions, so there is no need to eyeball it.

What Measurement Mistakes Should You Avoid?

Two mistakes account for most wrong results. The first is measuring the wrong thing, including a video player's frame, an app window's border, or a picture frame in its width and height instead of just the actual image or video content. That extra border can add 20 to 30 pixels without you noticing, which throws off the whole ratio.

The second is resizing only one side. Change the width but leave the height exactly where it was, or the other way around, and the result stretches or squishes. Always change both numbers together, using the resize formula above, or let the calculator do it for you.

What Are the Most Common Standard Aspect Ratios?

Is 2560x1440 a 16:9 aspect ratio?

Yes. 2560 divided by 1440 equals 1.78, which matches 16:9 exactly. This resolution is commonly called QHD or 1440p.

Is 1280x720 a 16:9 aspect ratio?

Yes. 1280 divided by 720 also equals 1.78, the same 16:9 shape at a lower pixel count. This resolution is usually labeled HD or 720p.

What Aspect Ratio Do Smartphones Use?

Most current phone screens are taller than 16:9. The iPhone 14, for example, has a screen ratio of roughly 19.5:9. That extra height gives more room to scroll and fit app content without making the phone any wider. Type 19.5 and 9 into the calculator above to see exactly how that shape compares to a standard 16:9 screen.

What Is the Difference Between Aspect Ratio and Pixels?

Aspect ratio is the shape. Pixels are the size. A 16:9 image stays 16:9 whether it is a small 320 by 180 thumbnail or a large 3840 by 2160 4K frame; the shape never changes even though the pixel count is completely different. Resolution, meaning the total pixel count, is what determines how sharp or detailed an image looks. Aspect ratio has nothing to do with sharpness, only with proportion.

Should You Crop or Pad When Aspect Ratios Do Not Match?

When your content's ratio does not match the space it needs to fill, there are two options.

Cropping cuts away the edges so the content fills the entire frame. Use this when the center of the image or video matters most and losing some of the edges will not hurt it.

Padding, also called letterboxing, adds black bars instead of cutting anything, keeping the full image visible inside a differently shaped frame. Use this when every part of the content needs to stay visible and nothing can be lost.

Neither option is wrong; they solve different problems. Crop when the middle is the priority and pad when completeness is the priority.

What Are Common Mistakes When Calculating Aspect Ratio?

• Resizing only one dimension instead of both, which stretches or squishes the result.

• Treating resolution and aspect ratio as the same thing when resolution is pixel count and aspect ratio is shape.

• Measuring a video player frame or image border along with the actual content, adding pixels that are not really part of the image.

• Rounding a decimal ratio too early and matching it to the wrong standard format.

Which Aspect Ratio Should You Use for Different Platforms and Projects?

The right ratio depends on where your content is going. A video for YouTube needs a different shape than a story posted to Instagram, and a printed photo has different requirements than a screen you are shopping for. The sections below cover the most common situations, along with a few related calculations that come up once your ratio is sorted out.

What Aspect Ratio Should You Use for YouTube, Instagram, and TikTok?

Standard YouTube videos use 16:9, while YouTube Shorts use 9:16. Instagram feed posts work best at 1:1 or 4:5, and Instagram Stories and Reels use 9:16, the same vertical format TikTok uses for all of its videos. Matching the ratio a platform expects keeps your content from getting cropped or padded with bars you did not choose yourself.

How Do You Simplify an Aspect Ratio the Same Way You Simplify a Fraction?

Reducing 1920:1080 down to 16:9 uses the same greatest common factor method as simplifying a fraction like 24/108 down to 2/9. For numbers outside of pixel dimensions, comparing two ratios, or reducing any pair of numbers to their lowest terms, the Ratio Calculator and the GCF Calculator both handle that math directly.

How Is Resizing an Image Related to Percentage Change?

Shrinking a 1600-pixel-wide photo down to 400 pixels is also a 75 percent reduction. The aspect ratio stays exactly the same through that change; only the overall size shifts. To find the percentage difference between an original size and a new one, the Percentage Calculator works that out in one step.

How Does a Ratio Relate to a Proportion?

A ratio compares two numbers, while a proportion sets two ratios equal to each other, which is exactly what the resize formula on this page does behind the scenes. For solving a missing value across two related ratios rather than a single width or height, the Proportion Calculator is built for that specific problem.

How Do You Calculate Screen Size From a Diagonal Length?

Once you know your ratio, the diagonal measurement of a screen, usually the number printed on a TV or monitor box, is enough to work out the exact width and height. This is useful when shopping for a TV, monitor, or projector screen and comparing options by their actual dimensions rather than just the diagonal size. A dedicated screen size calculator is not live on this site yet, so for now the resize formula covered earlier on this page gets you most of the way there once you have one measured dimension.