- 1Enter the Original Width and Original Height of your image or screen, in pixels.
- 2Enter the New Target Width you want to resize to, in pixels.
- 3Read the Calculated New Height that keeps the proportions, plus the simplified Aspect Ratio (for example 16:9) below.
The Aspect Ratio Calculator finds the height that keeps an image or video in proportion when you change its width, and expresses the width-to-height relationship as a simplified ratio. It is useful when resizing photos, fitting video to a specific frame, or checking whether a screen resolution matches a standard shape such as 16:9 or 4:3. Aspect ratio is width divided by height; keeping it constant is what prevents stretching or squashing.
Calculated from the original dimensions and the new target width so the shape is preserved.
New Height = (New Width × Original Height) ÷ Original WidthWidth and height are reduced by their greatest common divisor (GCD). Decimal inputs are scaled to whole numbers, up to 8 decimal places, before reducing.
Ratio = (Width ÷ GCD) : (Height ÷ GCD)The ratio of new to original width equals the ratio of new to original height.
New Width ÷ Original Width = New Height ÷ Original HeightNew Height = (1280 × 1080) ÷ 1920 = 1,382,400 ÷ 1920 = 720. Ratio = 1920:1080 reduced by 120 = 16:9New Height = (600 × 800) ÷ 1200 = 400. Ratio = 1200:800 reduced by 400 = 3:2New Height = (1920 × 1080) ÷ 2560 = 810. Ratio = 2560:1080 reduced by 40 = 64:27- Keep width and height in the same unit (pixels). The tool does not convert units.
- Positive decimals are allowed. Decimal dimensions are scaled to whole numbers, up to 8 decimal places, before the ratio is simplified.
- Only Original Width, Original Height and New Target Width are used. There is no list of preset ratios — the ratio is derived from the numbers you enter.
- A non-standard ratio such as 64:27 simply means the dimensions do not reduce to a common shape like 16:9; it is not an error.
- Original width and height must both be greater than zero, or the tool shows 'Enter positive width & height dimensions'.
What does an aspect ratio of 16:9 mean?
For every 16 units of width there are 9 units of height. 1920×1080, 1280×720 and 3840×2160 all share the 16:9 shape.
How do I resize without distorting the image?
Change one dimension and let the calculator compute the other. As long as New Height = (New Width × Original Height) ÷ Original Width, the proportions are preserved.
Why is my ratio shown as something unusual like 43:18?
The width and height you entered do not reduce to a common ratio. The tool always divides both sides by their greatest common divisor, whatever that produces.
What units does the calculator use?
It is unit-agnostic but designed for pixels; the output height is labelled 'px'. Use the same unit for every field.
Can I enter the height I want instead of the width?
This calculator solves for height from a target width. To target a height, swap your width and height values in the original fields.