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Paper Enlargement Percentage Calculator

Copier scaling % between A4, A3, Letter & more

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Choose Paper sizes mode and pick your original size under From and the size you want under To — for example A4 to A3.
  2. 2.Read the copier zoom percentage shown (A4 to A3 is 141%, A3 to A4 is 71%), or switch to Custom size and type the original and target edge lengths in the same unit.
  3. 3.Set your photocopier or printer to that percentage, load the target paper, and make the copy.

About Paper Enlargement Percentage Calculator

The photocopy scaling percentage is the zoom you dial into a copier or printer so an image on one paper size fits another. For the ISO 216 A-series it comes down to two numbers: enlarging one step up (for example a4 to a3 enlargement) is 141%, and reducing one step down (a3 to a4, or a4 to a5) is 71%. This calculator gives you that number for any pair of standard sizes, or for a custom original-to-target measurement, so you can set the machine once and copy without trial and error.

Those 141% and 71% figures are not arbitrary. Every A-series sheet has the same 1:√2 (one to the square root of two) aspect ratio, and each size is the previous one cut in half across its long edge — A5 is half an A4, A4 is half an A3, and so on. Because area halves at each step, the length of each edge changes by √2 ≈ 1.41421. Enlarging therefore multiplies each edge by about 1.414 (141%), and reducing multiplies by 1/√2 ≈ 0.7071 (71%). The two values are reciprocals: enlarge at 141% then reduce at 71% and you are back where you started. The same ratio governs the B-series, which also uses 1:√2.

Skipping a size squares the factor. Going two steps up, such as A5 to A3, is 200% (an exact doubling of area is a √2 × √2 = 2 length factor), and two steps down, like A4 to A6, is 50%. That is why 141%, 71%, 200% and 50% are the fixed preset buttons on almost every office copier.

The tool works in two modes. In paper-sizes mode you pick a source and a target from A2 through A6, B4, B5, and the US sizes Letter (8.5 × 11 in), Legal (8.5 × 14 in) and Tabloid/Ledger (11 × 17 in); it returns the percentage that fits the whole source page onto the target. When the two shapes match — any A-to-A or B-to-B pairing — a single percentage fits both edges exactly. When the proportions differ, such as A4 to US Letter or Letter to Legal, one zoom cannot match both edges, so the tool reports the largest setting that still fits the entire page and tells you which edge will leave a margin. In custom mode you type the size you have and the size you want (the same edge, in any unit) and it returns target ÷ original × 100.

Use it whenever you photocopy, scale a print, or resize artwork: set the copier to the percentage shown, load the target paper, and copy. Everything is computed locally in your browser using the exact ISO 216 dimensions, so no measurements ever leave your device.

Frequently asked questions

What percentage do I use to enlarge A4 to A3?
Set the copier to 141%. A3 is exactly one size larger than A4, and each A-series step up multiplies every edge by the square root of 2 (about 1.414), which is 141% as a zoom setting. Loading A3 paper and copying an A4 original at 141% fills the A3 sheet.
What percentage reduces A3 to A4?
Use 71%. Reducing one A-series step multiplies each edge by 1/√2 ≈ 0.7071, which rounds to 71%. The same 71% also reduces A4 to A5 and A5 to A6, because every adjacent step uses the identical ratio.
Why are the copier presets 141% and 71%?
Because all A-series (and B-series) paper shares a 1:√2 aspect ratio and each size is the previous one halved. Halving the area changes each edge by √2 ≈ 1.41421, so enlarging one step is 141% and reducing one step is its reciprocal, 1/√2 ≈ 0.7071 or 71%. They are exact reciprocals, which is why enlarging then reducing returns the original size.
How do I scale a custom size that is not a standard paper?
Switch to Custom size mode, enter the edge length you currently have and the length you want it to become in the same unit, and the tool returns target ÷ original × 100. For example, going from 210 mm to 297 mm gives 141%, and 100 mm to 75 mm gives 75%.
Why does US Letter to Legal not give a clean percentage?
US Letter and Legal have different proportions (both are 8.5 inches wide but 11 versus 14 inches tall), unlike the A-series which all share one shape. A single zoom cannot match both edges, so the calculator reports the largest percentage that still fits the whole page and notes that the shorter side will leave a margin.

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