Comprehensive Calculator Guide
To resize an image or video without distortion, keep width and height in proportion: new height = new width × original height ÷ original width. A 1920 × 1080 image scaled to 1280 wide becomes 720 high, a 16:9 ratio. Enter the original size and new width to get the height and the reduced ratio.
Ratios and where they are used
The ratio is width:height reduced by the greatest common divisor: 1920 and 1080 share 120, giving 16:9. Scaling in proportion keeps the ratio; only the pixel count changes.
16:9 suits screens and YouTube; 9:16 is the same shape upright, for stories and short vertical video (1080 × 1920). 4:5 is the portrait post format on Instagram (1080 × 1350), 1:1 is square, 4:3 is common for phone and tablet photos, 3:2 for cameras, 21:9 for ultrawide screens.
When ratios differ
Fitting a 16:9 video into a 9:16 frame needs cropping or padding; resizing alone will not do it, and stretching each side independently distorts faces. Pixels are whole, so the height is rounded, and some video encoders require even dimensions: nudge the width if the height comes out odd.
How to Use
- 01Enter the original width and height in pixels.
- 02Enter the new width.
- 03Read the new height and the reduced ratio; to work from a height, swap the fields.
Formula Used
New height = new width × original height ÷ original width | Ratio = width ÷ GCD : height ÷ GCDPractical Examples
Example 1: HD video
1920 × 1080 to 1280 wide: 720 high, 16:9.
Example 2: portrait post
1080 × 1350 to 720 wide: 900 high, 4:5.
Example 3: vertical story
1080 × 1920 to 720 wide: 1280 high, 9:16.
Important Tips
- Work at the highest resolution you need and scale down; scaling up loses sharpness.
- Keep key content centred when one image must serve several formats.
Common Mistakes to Avoid
- Changing width and height independently, which distorts the image.
- Confusing 16:9 (landscape) with 9:16 (portrait).
Frequently Asked Questions
- How do I find an image's aspect ratio?
- Divide width and height by their greatest common divisor: 1920 × 1080 is 16:9.
- What size is a vertical story?
- Usually 1080 × 1920 pixels, 9:16.
- Why do I get an odd ratio like 683:384?
- The size does not match a standard ratio exactly. 1366 × 768 is 683:384, very close to 16:9.
- How do I resize without distortion?
- Change one dimension and compute the other with the same ratio, as this calculator does.