What percentage enlarges A4 to A3?

Set the copier to 141%. A3 is exactly one A-series step larger than A4, and each step up multiplies every edge by √2, which rounds to 141% on a copier display. 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 every edge by 1/√2, which rounds to 71% on the machine. The same 71% setting also reduces A4 to A5 and A5 to A6, because every adjacent step in the series uses the identical ratio.

Why are 141%, 71%, 200%, and 50% the fixed preset buttons on copiers?

All A-series and B-series paper shares a 1:√2 aspect ratio and each size is the previous one halved in area. 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%. Skipping a size squares the factor: two steps up is 200% and two steps down is 50%.

How do I scale a custom size that is not standard paper?

Switch the calculator to Custom size mode, enter the edge length you currently have and the edge length you want 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 Letter to Legal not give a clean percentage?

US Letter and Legal share the same 8.5-inch width but differ in height, so they do not have the same aspect ratio. A single zoom cannot match both edges at once, so the calculator reports the largest percentage that still fits the entire page and tells you which edge will leave a margin.

Can I use the chart for B-series paper?

Yes. The B-series uses the same 1:√2 ratio as the A-series, so B5 to B4 is 141%, B4 to B5 is 71%, B6 to B4 is 200%, and B4 to B6 is 50%. For mixed A-to-B pairings, use the calculator's Custom size mode.

A4 to A3 Enlargement Percentage Chart: Full Reference

The enlargement percentage from A4 to A3 is 141%, which is the same setting most office copiers list as a preset button under names like "A4→A3" or "A3." Set your copier to 141%, load A3 paper, and a full A4 original will fill the new sheet edge to edge. Reducing A3 back to A4 uses the reciprocal value of 71%, and the identical 71% setting also reduces A4 to A5, A5 to A6, and so on down the ISO 216 series. These four fixed numbers, 141%, 71%, 200%, and 50%, appear as preset buttons on almost every photocopier because every adjacent pair of A-series sheets shares the same aspect ratio and the same length ratio.

Anyone who copies between mixed paper sizes, drafts posters, prints artwork, or rescales a Letter document onto A4 needs a single quick reference that lists the right percentage for every common pair. This guide gives you that reference as a chart, explains the geometry behind the numbers, and shows how the Paper Enlargement Percentage Calculator returns the exact figure for any paper pair, including custom measurements.

a4 to a3 enlargement percentage chart — A4 to A3 Enlargement Percentage Chart: Full Reference

The full A-series enlargement and reduction percentage chart

The table below lists the copier zoom percentage you should dial in for every adjacent and two-step pair within the ISO 216 A-series. The percentages come from the √2 relationship that defines the standard, so they are not approximations. The Paper Enlargement Percentage Calculator uses the exact ISO 216 dimensions to compute these values, so you can confirm any row instantly.

From	To	Copier setting	Action
A5	A4	141%	Enlarge one step up
A4	A3	141%	Enlarge one step up
A3	A2	141%	Enlarge one step up
A4	A5	71%	Reduce one step down
A3	A4	71%	Reduce one step down
A2	A3	71%	Reduce one step down
A5	A3	200%	Enlarge two steps up
A4	A2	200%	Enlarge two steps up
A3	A1	200%	Enlarge two steps up
A6	A4	200%	Enlarge two steps up
A4	A6	50%	Reduce two steps down
A3	A5	50%	Reduce two steps down
A2	A4	50%	Reduce two steps down
A1	A3	50%	Reduce two steps down

Skipping more than two sizes multiplies those factors further. Three steps up is 141% × 141% ≈ 200% × 141% ≈ 283%, and three steps down is roughly 35%. For any combination not shown above, use the calculator's Custom size mode and type the edge length you have and the edge length you want in the same unit.

Why 141% and 71% appear on every office copier

The ISO 216 A-series, which includes A4, A3, A5, and every other A-size, is built around a single geometric rule. Every sheet in the series has the same aspect ratio: 1 to the square root of 2, written 1:√2, which is approximately 1:1.4142. Each size in the series is the previous size cut in half across its longer edge. A5 is half an A4, A4 is half an A3, A3 is half an A2, and so on in both directions.

Because each step halves the area, every edge of the new sheet is exactly 1/√2 ≈ 0.7071 times the edge of the previous sheet, and the next size up is √2 ≈ 1.4142 times larger. Translate those ratios into copier percentages and you get 141.4% for enlarging one step up (rounded to 141% on the copier's display) and 70.7% for reducing one step down (rounded to 71%). The two values are reciprocals: enlarge an A4 to A3 at 141% and immediately reduce that copy back at 71%, and you return to a near-exact A4. Skipping a size squares the factor. Two steps up multiplies the edge by √2 × √2 = 2, which is exactly 200%, and two steps down multiplies by 0.5, which is exactly 50%. That is why 141%, 71%, 200%, and 50% sit as the four fixed preset buttons on most machines.

The same 1:√2 ratio also governs the ISO 216 B-series, so the B4 to B5 reduction and the B5 to B4 enlargement use the same 71% and 141% settings.

How to find your percentage with the Paper Enlargement Percentage Calculator

For any pair of standard sizes, or for any custom measurement you need to scale, the calculator returns the exact copier zoom in a few clicks.

Open the Paper Enlargement Percentage Calculator and leave the default Paper sizes mode selected.
Pick your original size from the From list, for example A4, and pick the target size under To, for example A3.
Read the percentage the tool displays. A4 to A3 shows 141%, and A3 to A4 shows 71%. Use the percentage exactly as the tool reports it.
For non-standard artwork or media, switch to Custom size mode, enter the original edge length in any unit, and enter the target edge length in the same unit. The tool applies target ÷ original × 100 and shows the result.
On your photocopier or printer driver, open the Scale or Zoom setting, type in the percentage, load the target paper, and make your copy.

Everything is computed locally in your browser using the exact ISO 216 dimensions, so no measurements leave your device.

When one clean percentage is not possible

The chart above works cleanly for any A-to-A or B-to-B pairing because every sheet within one series shares the same proportions. The math breaks down the moment you cross between systems that do not share an aspect ratio. US Letter is 8.5 × 11 inches and US Legal is 8.5 × 14 inches. Both share the same 8.5-inch width but differ in height, so one zoom cannot fit a Letter original onto Legal edge to edge in both directions at once. The same issue appears with A4 to US Letter, where the European and North American standards have similar but not identical proportions.

In those cases the Paper Enlargement Percentage Calculator reports the largest percentage that still fits the entire source page on the target, then flags which edge will leave a margin. You can still copy successfully: you just get a small blank strip on one side. If you need a borderless fit, the only options are to use the nearest standard size in the same system or to trim or pad the original before copying.

Tips for getting a perfect copy every time

Always measure the edge you intend to scale along when switching between systems, and confirm both source and target paper are loaded in the correct tray orientation. If your copier rounds to whole numbers, prefer the percentage the calculator gives you rather than a preset button. Preset buttons assume standard ISO dimensions; if your source or target is a custom trim size, the preset will be slightly off and you will get unwanted margins or clipped content. Test the first copy at 50% to confirm paper orientation before running a full batch, especially when you are reducing two or more steps. Finally, store the calculator's percentage in a small note inside the copier lid so the next person to use the machine does not have to re-derive it. If A4 to A3 is the only conversion you do, the deep-dive in our guide on enlarging A4 to A3 with the right copier zoom percentage walks through that single case in more detail.

For a deeper look, see How to Calculate Percentage of a Number (With Examples).