Image Scale Percentage Calculator
When you resize an image, knowing the exact scale percentage keeps the result sharp and correctly proportioned, and this image scale percentage calculator works it out in one step. Enter the original dimension and the new dimension you want, in whatever unit you like as long as both match, and the tool divides the new by the original and multiplies by 100 to give the scale as a percentage. A result above 100% tells you the image is being enlarged, while below 100% tells you it is being shrunk, so you can see at a glance how aggressive the change is. The real value of working in percentages is that the same figure can be applied to both width and height to keep the aspect ratio intact, which prevents the stretched or squashed look that comes from scaling each side by a different amount. The percentage method works identically for pixels, inches or centimeters, so it suits screen graphics and print sizing alike. Because original and target sizes vary with every job, both inputs are fully editable rather than fixed. The calculation is a single division followed by multiplying by 100, shown in the formula below, with a worked example that reconciles exactly to the calculator defaults.
Scale percentage compares new size to original: scale % = new / original x 100. Resizing a 800 unit image to 1,200 units is a scale of 150.00%, an enlargement.
Image scale percentage formula
Scale % = (N / O) x 100
N = new dimension
O = original dimension
Above 100% enlarges, below 100% shrinks
Dividing the new dimension by the original gives the ratio of the two sizes, and multiplying by 100 expresses that ratio as a percentage of the original.
Worked example
An image that is 800 pixels wide is being resized to 1,200 pixels wide.
- Ratio = 1,200 / 800 = 1.5
- Scale % = 1.5 x 100 = 150%
The image is scaled to 150%, an enlargement. These are the calculator's default inputs, so the result above matches the widget exactly.
Image scale percentage calculator: frequently asked questions
How do I find the scale percentage for an image?
Divide the new size by the original size and multiply by 100. If an image that was 800 pixels wide becomes 1,200 pixels wide, the scale is 1,200 / 800 x 100, which equals 150%. A result above 100% means you are enlarging the image, while below 100% means you are shrinking it.
Will scaling distort my image?
Only if the width and height are scaled by different percentages. To keep the proportions correct, apply the same scale percentage to both dimensions. This calculator finds the percentage from one dimension pair, and using that same percentage on the other dimension preserves the aspect ratio so the picture is not stretched or squashed.
Does enlarging an image reduce quality?
Enlarging a raster image above 100% spreads the existing pixels over a larger area, which can make it look soft or blocky because no new detail is created. Shrinking generally looks fine. For large enlargements, start from the highest resolution source you have, or use a vector format that scales without losing sharpness.
Can I use this for print sizing too?
Yes. The same percentage method works whether you measure in pixels, inches or centimeters, as long as both sizes use the same units. Find the scale from your target dimension against the original, then apply it to set the print or canvas size. Just keep an eye on resolution so an enlargement does not drop below a usable dots-per-inch.
What is the image scale percentage formula?
Scale percentage equals the new dimension divided by the original dimension, multiplied by 100. With a new width of 1,200 and an original width of 800, that is 1,200 / 800 x 100, which equals 150%.
Official sources
- Measurement and units guidance: US National Institute of Standards and Technology (NIST). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.