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Video Resolution Calculator

Video & AudioVideo Converters and Compression
Resize by

The side you chose above; the other side is worked out to keep the ratio.

New resolution —
Aspect ratio
—
Ratio as decimal
—
Common name
—
Pixels per frame
—
Megapixels
—
Scale vs source
—

To rescale a video without distortion, multiply the target side by the source ratio: new height = new width × source height ÷ source width. For a 1920 × 1080 clip resized to 1280 wide, 1280 × 1080 ÷ 1920 = 720, giving 1280 × 720. Encoders using 4:2:0 chroma need both sides even, so odd results are rounded to the nearest even pixel.

About this tool

Editors exporting proxies, streamers picking an output canvas and anyone preparing clips for a platform with a size limit all face the same question: if one side changes, what must the other be so the picture does not stretch? Enter the source width and height, choose which side the destination fixes, and type that number. The calculator reduces the source to its simplest ratio, works out the missing side, rounds it to an even pixel count, and reports the pixels per frame, megapixels, scale relative to the source and the usual name of the result when it matches a broadcast or streaming raster. It assumes square pixels; anamorphic formats such as DV with a 0.9 or 1.2 pixel aspect need the display size, not the stored size, as the source.

How to use it

  1. Enter the source frame

    Type the width and height in pixels of the clip or project you are starting from.

  2. Pick the fixed side

    Choose New width or New height depending on which dimension the destination dictates.

  3. Type the target size

    Enter the pixel count for that side; the other side and the stats update as you type.

  4. Read the warnings

    A note appears when the exact answer was not a whole even number, so you know the ratio is off by a fraction of a pixel.

Examples

1920×1080 to 1280 wide

Source width
1920
Source height
1080
Resize by
New width
Target size
1280

Result New resolution: 1280 × 720
Aspect ratio: 16:9
Ratio as decimal: 1.7778
Common name: HD (720p)
Pixels per frame: 921,600
Megapixels: 0.92
Scale vs source: 66.7%

  1. Aspect ratio = 1920:1080 ÷ 120 = 16:9 (1.7778:1)
  2. New height = 1280 × 1080 ÷ 1920 = 720
  3. Rounded to an even number: 720 px

Downscaling a Full HD master to 1280 pixels wide gives the standard 720p frame, with 44% of the source's pixel count.

Full HD to 2160 tall

Source width
1920
Source height
1080
Resize by
New height
Target size
2160

Result New resolution: 3840 × 2160
Aspect ratio: 16:9
Ratio as decimal: 1.7778
Common name: 4K UHD (2160p)
Pixels per frame: 8,294,400
Megapixels: 8.29
Scale vs source: 200%

  1. Aspect ratio = 1920:1080 ÷ 120 = 16:9 (1.7778:1)
  2. New width = 2160 × 1920 ÷ 1080 = 3840
  3. Rounded to an even number: 3840 px

Doubling the height of a 16:9 frame doubles the width as well, landing on 3840 × 2160 UHD with four times the pixels.

640×480 to 360 tall

Source width
640
Source height
480
Resize by
New height
Target size
360

Result New resolution: 480 × 360
Aspect ratio: 4:3
Ratio as decimal: 1.3333
Common name: Custom size
Pixels per frame: 172,800
Megapixels: 0.17
Scale vs source: 75%

  1. Aspect ratio = 640:480 ÷ 160 = 4:3 (1.3333:1)
  2. New width = 360 × 640 ÷ 480 = 480
  3. Rounded to an even number: 480 px

A 4:3 VGA clip scaled to 360 lines keeps the 4:3 shape at 480 pixels wide, not the 640 a 16:9 360p frame would use.

How it is calculated

new height = new width × H ÷ W; new width = new height × W ÷ H; ratio = W ÷ gcd(W, H) : H ÷ gcd(W, H)

W
source width in pixels
H
source height in pixels
gcd
greatest common divisor, used to reduce the ratio

Keeping the aspect ratio means the width-to-height quotient stays the same, so the unknown side is the known side multiplied by the source quotient. The exact value is then rounded to the nearest even integer, because H.264, H.265 and most players subsample colour in 2 × 2 blocks for 4:2:0 video and refuse odd dimensions. The ratio is shown in lowest terms by dividing both sides by their greatest common divisor, so 1920 × 1080 becomes 16:9 and 1440 × 1080 becomes 4:3.

When not to use it

  • Anamorphic sources with non-square pixels need their display size entered, not the stored frame size.
  • Converting to a different aspect ratio on purpose calls for a crop or letterbox plan, not proportional scaling.

Common mistakes

  • Entering the target width while Resize by is set to New height gives a frame that is far too large.
  • Rounding to an odd number such as 1000 × 563 makes many H.264 encoders fail or pad the frame.
  • Assuming 480p is always 640 × 480 ignores that widescreen 480p is 854 × 480.

Frequently asked questions

Why is the result rounded to an even number?

Most delivery codecs store colour at half resolution in both directions (4:2:0). Each chroma sample covers a 2 × 2 block of pixels, so the frame width and height must be divisible by 2. FFmpeg with libx264 stops with an error such as 'height not divisible by 2' otherwise.

What resolution is 720p at 16:9?

1280 × 720 pixels, defined in SMPTE ST 296. It holds 921,600 pixels per frame, about 44% of a 1920 × 1080 frame.

How do I find the ratio of an unusual size like 2560 × 1080?

Enter it as the source. The greatest common divisor of 2560 and 1080 is 40, giving 64:27, which is the exact form of the marketing label 21:9. The decimal 2.3704 shows how wide it really is.

Does upscaling add detail?

No. Scaling 1080p to 2160p quadruples the pixel count but the extra pixels are interpolated from the existing ones. It can help a platform pick a higher bitrate tier, but the picture holds no new information.

Why does my vertical video come out wrong?

Check that width and height are in the right order. A phone clip is 1080 wide and 1920 tall; entering it as 1920 × 1080 treats it as landscape and the scaled size will be rotated.

What is the difference between 4K UHD and DCI 4K?

UHD is 3840 × 2160, exactly twice 1920 × 1080 in each direction at 16:9. DCI 4K, used in cinema, is 4096 × 2160, a ratio of about 1.90:1. The calculator names both when the result matches.

Cite this tool

Using this tool in an assignment, article or report? Copy a citation, or a link for your website.

APA

Tools Directory Editorial Team. (2026, October 24). Video Resolution Calculator. Tools Directory. Retrieved October 26, 2026, from https://tools.milunir.com/video-audio/video-converters-and-compression/video-resolution-calculator/

MLA

Tools Directory Editorial Team. “Video Resolution Calculator.” Tools Directory, 24 Oct. 2026, https://tools.milunir.com/video-audio/video-converters-and-compression/video-resolution-calculator/. Accessed 26 Oct. 2026.

Chicago

Tools Directory Editorial Team. “Video Resolution Calculator.” Tools Directory. Last modified October 24, 2026. Accessed October 26, 2026. https://tools.milunir.com/video-audio/video-converters-and-compression/video-resolution-calculator/.

Link<a href="https://tools.milunir.com/video-audio/video-converters-and-compression/video-resolution-calculator/">Video Resolution Calculator – Tools Directory</a>