Pencil-to-Page Size Guide
Pick the ISO paper size your drawing is on and the size you want to scale it to — get the exact scale factor and a practical lead-width recommendation for the new format.
Scale from A4 to A2
Recommended lead for A2: A 0.7mm or 0.9mm mechanical pencil, or a woodcase pencil kept to a broad sharpened point.
The A-series, briefly
ISO 216 defines A0 as a sheet with an area of exactly one square metre, in a 1:√2 ratio. Every smaller size — A1, A2, A3 and so on — is made by folding the previous size in half along its long edge, which preserves the same aspect ratio at every step. That's the whole reason a photocopier can enlarge an A4 page to A3 with nothing cut off: the proportions never change, only the scale.
This tool uses the official rounded millimetre dimensions for A0 through A6 to compute the exact linear and area scale factor between any two sizes in the series.
Frequently Asked Questions
Why does moving up two A-sizes exactly double the drawing?
The ISO 216 system is built so each size is exactly half the area of the one before it, and every size shares the same 1:√2 aspect ratio. Halving the area twice doubles the linear dimensions exactly, which is why A4 to A2 is a clean ×2 scale, while a single step (A4 to A3) scales by 1/√2 ≈ 0.707 in the other direction.
Why isn't A4-to-A0 exactly ×4?
The published ISO 216 millimetre dimensions are rounded to the nearest whole millimetre, so tiny rounding differences creep in over multiple steps. A4 to A0 comes out to about ×4.003 rather than a mathematically perfect 4 — close enough for planning a drawing, but worth knowing if you need millimetre-exact figures.
Why recommend a different lead width for a bigger page?
A very fine 0.3mm lead takes a long time to cover a large sheet and wears down constantly under heavier strokes, while a broad 2mm clutch lead is too coarse for delicate detail on a small page. Matching the lead width to the format keeps blocking-in fast on big work and keeps fine passes precise on small work.
Does this work for non-ISO sizes like US Letter?
Not directly — Letter, Legal, and Tabloid follow a different (non-√2) ratio, so their scale factors between each other aren't the clean powers of √2 that ISO sizes have. This tool is built specifically around the ISO A-series used almost everywhere outside North America.
Educational tool only. Lead-width recommendations are general studio guidance — personal drawing style and the amount of detail in your subject matter more than the paper size alone.