How is the missing dimension calculated?

The tool keeps the source aspect ratio (width divided by height) constant. If you enter a target width, the height is target width divided by the source aspect ratio, rounded to the nearest pixel.

What do the presets set?

Each preset (720p, 1080p, 1440p, 4K) sets the target width to that standard's pixel width (1280, 1920, 2560, or 3840) and switches the mode to target width, so the height is computed from your source aspect ratio.

Why is my scaled height not a whole number?

Some source aspect ratios do not divide evenly into a target dimension. The tool rounds to the nearest whole pixel, which can shift the aspect ratio very slightly.

What is the difference between scaling by percentage and by target width?

Scaling by percentage multiplies both dimensions by the same factor. Scaling by target width or height instead fixes one dimension and derives the other, which is useful when you have a hard constraint like a container width.

Does this resample the actual image or video?

No. This only calculates the resulting pixel dimensions. Use image or video editing software to perform the actual resize.

How many megapixels is 1920x1080?

1920 multiplied by 1080 is 2,073,600 pixels, or about 2.07 megapixels.

Resolution Scaling Calculator

Enter a source width and height, then a target width, height, or scale percentage, to get the scaled resolution with aspect ratio preserved.

Source Resolution

Width (px)

Height (px)

Scale To

Target Width (px) Presets

Enter a source resolution and target value to see results

Summary

Scaling a resolution means changing its pixel dimensions while keeping the same width-to-height ratio, so the image or video does not stretch or squash. This calculator takes a source width and height and a single target value, either a target width, a target height, or a scale percentage, then computes the missing dimension from the source aspect ratio. It also reports the resulting pixel count and megapixels so you can judge the output size at a glance.

How it works

Enter the source width and height in pixels, or pick a preset.
Choose what you are scaling to: a target width, a target height, or a scale percentage.
Enter that one target value.
The tool computes the missing dimension using the source aspect ratio, so proportions stay correct.
Results show the scaled width, height, exact pixel count, megapixels, and the effective scale percentage.

Use cases

Resize a photo to a target width for a website without distorting it.
Figure out the height when downscaling a video to 1080p or 720p.
Check the resulting megapixel count before exporting a scaled image.
Scale a design mockup down by a percentage while keeping proportions.
Compare how a source resolution maps onto common output presets like 4K.
Plan thumbnail dimensions that match a fixed width or height constraint.

Frequently Asked Questions

Last updated: 2026-09-09 · Reviewed by Nham Vu