Image-resize dimensions
Work out the correct height for a resized image so it keeps its original proportions, given a new width.
Result
New height (keeping aspect ratio)
How to use this calculator
- Enter the image's original width and height.
- Enter the new width you want.
- Read the matching height that keeps the image's proportions.
Assumptions
- Assumes you want to preserve the exact original aspect ratio — cropping to a different ratio needs a separate decision about what to cut.
Technical details: what the fields mean
- Original width
originalWidth - The image's current width in pixels.
- Original height
originalHeight - The image's current height in pixels.
- New width
newWidth - The width you want to resize to.
Methodology
New height = new width × (original height ÷ original width) — keeps the same width-to-height ratio as the original.
Worked example
1600×900px image resized to 800px wide
Inputs: originalWidth=1600, originalHeight=900, newWidth=800
Result: 450px height
Practical guidance
- Most image editors and CSS frameworks have a 'lock aspect ratio' option that does this automatically — use this calculator when you need the exact number ahead of time.
Common mistakes
- Manually entering both a new width and a new height without checking they match the original ratio, which stretches or squashes the image.
FAQs
How do I resize an image without distorting it?
Only specify one new dimension (width or height) and calculate the other using the original ratio — this calculator does that for you.