Aspect Ratio Resize Calculator
Resize an image or video without distortion: enter the original dimensions and a new width to get the matching height, the simplified ratio and the new megapixels.
How it works
new height = new width × (original height ÷ original width) · ratio = original W : original H reduced by their greatest common divisor · megapixels = (new W × new H) ÷ 1,000,000
To resize without stretching, the new dimensions must keep the same ratio of width to height as the original. Fix the new width and the height follows from multiplying by the original height-to-width ratio; anything else squashes or stretches the picture. Reducing the original width and height by their greatest common divisor gives the familiar named ratio — 1920×1080 reduces to 16:9, 1024×768 to 4:3 — which is handy for matching a target frame, print size or video standard.
Worked example
A 1920×1080 image (16:9) resized to a new width of 1280 px gets a height of 1280 × (1080 ÷ 1920) = 1280 × 0.5625 = 720 px, giving 1280×720 — still 16:9, and about 0.92 megapixels.
Frequently asked questions
How do I keep an image from looking stretched?
Change width and height together in the same proportion. Set the new width, let the calculator derive the matching height, and the picture keeps its shape. Editing one dimension freely while forcing the other distorts the image.
What does the simplified ratio tell me?
Dividing the width and height by their greatest common divisor gives the named aspect ratio, like 16:9 or 3:2. It lets you check whether an image matches a target frame or crop before you resize.
Why does the new height sometimes round?
Pixels are whole units, so a scaled height rarely lands on an exact integer. The result is rounded to the nearest pixel, which is imperceptible; for pixel-perfect work, choose a new width that divides evenly by the ratio.
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This calculator is for educational purposes. Double-check important results before acting on them.