Image Resize Calculator
Enter the original width and height, then set one new size to get the other, with the aspect ratio kept. Pixels are whole numbers, so the result is rounded; the tool shows how much the ratio changes.
How the new size is calculated
The new size keeps the aspect ratio (width ÷ height) of the original.
- Set the width: new height = original height × new width ÷ original width.
- Set the height: new width = original width × new height ÷ original height.
- Set the long side or the short side: the longer (or shorter) side becomes the value you enter, and the other side is calculated from it. This works for portrait images as well as landscape ones.
- Set a scale in percent: the width and the height are each multiplied by the scale.
Pixels are whole numbers, so a result with a fraction is rounded the way you choose (to nearest, down or up). The side you set stays exactly as entered; with a scale, both sides are rounded.
Why the aspect ratio can change slightly
Rounding to whole pixels can make the new aspect ratio differ a little from the original. The tool shows this as a percentage: how much larger (+) or smaller (−) the new width ÷ height is than the original width ÷ height. A change of 0.00% means the ratio is exactly the same.
For example, resizing 1,000 × 333 pixels to a width of 100 gives a height of 33.3, which is rounded to 33. The new 100 × 33 image is about 0.91% wider than the original. The difference matters less the larger the image is.
Examples
- 4,000 × 3,000, width 1,600: 1,600 × 1,200 (scale 40%).
- 1,920 × 1,080, long side 1,280: 1,280 × 720 (scale 66.67%).
- 4,000 × 3,000, scale 25%: 1,000 × 750.
- 1,000 × 333, width 100: 100 × 33 (the aspect ratio changes by about +0.91%).
Notes
- Width, height, long side and short side must be whole numbers from 1 to 999,999. A scale must be greater than 0, with up to 2 decimal places. Commas are accepted only as thousands separators.
- If the new size would be 0 pixels (too small) or more than 999,999 pixels, the tool cannot calculate it.
- The tool only calculates pixel counts. How the picture looks after resizing (blur when enlarging, lost detail when shrinking) depends on the image and the software you use.
- Recommended image sizes for specific websites and apps change often, so they are not included.
- To find the ratio itself, use the Aspect Ratio Calculator. For the relation between pixels and physical size, see the PPI Calculator.
Frequently asked questions
How do I resize an image without stretching it?
Set one new size and work out the other from the original ratio. This tool does that when you set the width, height, long side, short side or a scale.
Why is the ratio slightly off?
Pixels must be whole numbers, so the calculated size is rounded. The difference gets smaller as the image gets larger.
When should I use the long side?
When you have a mix of portrait and landscape pictures and want the longer side of each to match a size. For a portrait picture, the long side is the height.