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Trim Marks

Proportional Scale Calculator

The percentage, the new size, and whether it crops.

Original size

Any unit, as long as both boxes use the same one. Ratio 3:2.

Result

If the original is pixels

  • At 300 ppi4.00 in
  • At 150 ppi8.00 in
  • Effective ppi at 8in150

Scaling up past 100% does not add detail — it invents it. For print, aim to place images at 100% or below at 300 ppi; anything much beyond that will show.

The digital version of the circular scale wheel that used to live on every studio wall. Enter the original size and what you need — a width, a height, a percentage, or a box to fit or fill — and get the scaling percentage and the resulting dimensions. Fill mode tells you exactly how much will be cropped.

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Why use this tool?

Five modes

To width, to height, by percentage, fit inside a box, or fill a box.

Tells you what crops

Fill mode reports how much falls outside the box in each direction.

Print resolution

Shows the physical size at 300 and 150 ppi, and the effective resolution at a given width.

Ratio simplified

1920 × 1080 comes back as 16:9.

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How this proportional scale calculator works

The percentage is simply the target divided by the original. What the tool adds is doing it in both directions at once, so you see the dimension you did not specify — which is the one that overflows the frame you were fitting into.

Fit and fill are the two useful box behaviours and they differ in which axis wins. Fit takes the smaller of the two ratios so the whole image lands inside the box, usually leaving a gap. Fill takes the larger so the box is covered, and the overflow is cropped. The tool reports exactly how much falls outside, because that is the number that decides whether the crop is acceptable.

Resolution is the thing scaling quietly destroys. An image placed at 200% has half the effective resolution it had, and past 100% you are not revealing detail — the software is inventing it. The panel shows the physical size at 300 and 150 ppi so you can see whether the scaled version still has the resolution the job needs.

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How to use it

  1. Step 1: Enter the original size

    Any unit, as long as both boxes match.

  2. Step 2: Choose what you are doing

    Fit keeps everything visible; fill crops.

  3. Step 3: Read the percentage

    That is the number to type into your layout application.

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Example usage

Placing a photo
An image scaled to a known column width, with the resulting depth checked against the space on the page.
Fitting a logo
Fit mode into a fixed frame, so nothing is cropped and the clear space is preserved.
Checking print resolution
A scanned file scaled up, with the effective ppi checked before it goes anywhere near a press.
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Resolution, upscaling and what AI changed

The old rule was simple and nearly absolute: you could scale an image down freely and scale it up only slightly, because enlargement spreads existing detail thinner and interpolation invents pixels by averaging neighbours. Anything past about 120% looked soft, and the only real fix was a better original.

Machine-learning upscalers genuinely changed part of that. Rather than averaging neighbours, they reconstruct plausible detail from what they learned about similar images. On photographic subjects — foliage, skin, fabric — the results can be very good, and a 200% enlargement that would have been unusable is now often acceptable in print.

The word doing the work there is plausible. The model is synthesising detail that was not captured, and on anything where accuracy is the point — a logo, small text in a screenshot, a product photograph, a face that has to be that person's face — it can invent confidently and wrongly. Use it where the detail is texture, and get a proper original where the detail is information. The resolution figures on this page still tell you which situation you are in.

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Frequently asked questions

What is the difference between fit and fill?

Fit scales until the whole image is inside the box, which usually leaves a gap on one axis. Fill scales until the box is covered, which crops the overflow. Fit for a logo, fill for a background.

Can I scale an image up?

You can, but past 100% you are inventing detail rather than revealing it. For print, aim to place images at 100% or below at 300 ppi.

What resolution do I need for print?

300 ppi at final size is the usual specification for quality litho. Large-format work viewed from a distance can go far lower — a billboard might be 20 ppi and look perfect.

Can AI upscaling replace a high-resolution original?

For texture, often. For information, no. An upscaler reconstructs plausible detail rather than recovering real detail, which is fine on foliage or fabric and unreliable on logos, small text, product shots and faces, where it can invent confidently and wrongly. Where accuracy matters, get the original file.

What is the difference between ppi and dpi?

Pixels per inch describes an image; dots per inch describes a printing device. They get used interchangeably and it rarely causes harm, but a press laying down 2,400 dpi is not contradicting a 300 ppi image — it is using many tiny dots to reproduce each pixel as a halftone.

What resolution does large-format work need?

Far less than print, because it is read from further away. A billboard viewed from tens of metres can be 20 ppi and look sharp; an exhibition panel read at arm's length wants something near photographic quality. The honest input is viewing distance, not the physical size of the piece.

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