Aspect Ratio Resize Calculator
Find the width or height that keeps an image the same shape when you resize it.
Proportion to keep
Resizing without distortion means keeping the same shape. Either give the aspect ratio — 16:9 for standard widescreen, 21:9 for ultrawide — or the dimensions you are starting from.
Common ratios
New size
The height is calculated to keep the proportion.
New dimensions
1,600 × 900
At 1,600 px wide, 16:9 gives a height of 900 px. The whole-pixel result matches the ratio exactly.
New dimensions 1,600 by 900 pixels.
Proportion
Details
- Ratio used16:9
- Exact calculated value900 pxAlready a whole pixel
- Total pixels1,440,000
Formula and assumptions
For a ratio A : B
heightequalswidth × B ÷ A
widthequalsheight × A ÷ B
Scale against the original
scaleequalsnew width ÷ original width × 100
Assumptions
- Ratio terms may be decimals, so 1.85:1 and 2.39:1 are used exactly as entered.
- The exact mathematical result is calculated first. Whole-pixel values are rounded to the nearest pixel afterwards and shown alongside the exact figure.
- A rounded whole-pixel result does not preserve the ratio perfectly. The difference is normally well under one pixel.
Questions
Why is the calculated dimension sometimes not a whole number?
Ratios divide exactly only at certain sizes. 16:9 at 1000 px wide gives 562.5 px, which is not a whole pixel. The calculator shows the nearest whole pixel as the practical answer and the exact value beneath it, so you can see the small difference.
Can I use a decimal ratio such as 2.39:1?
Yes. Cinema ratios are conventionally written as a decimal against 1, and they are used exactly as entered. They are never converted into an invented whole-number fraction.
What is the difference between the two entry modes?
Ratio mode takes the proportion directly, such as 16:9. Existing dimensions mode takes a size you already have, such as 1920 × 1080, and keeps that exact proportion. Existing dimensions mode also reports the scale as a percentage of the original.
Does resizing to these dimensions change quality?
This calculator works out geometry only. Enlarging beyond the original pixel dimensions cannot add detail that was not captured, but that is a property of the image, not of the ratio.