TL;DR
A writer describes using a sheet of A4 paper as an ad-hoc measuring device and explains why the A-series paper sizes have their particular dimensions. The piece shows a hands-on example: estimating a monitor's diagonal with folded A4 sheets and basic arithmetic.
What happened
In a short essay, the author outlines a personal, informal method for measuring objects using a sheet of A4 paper. The piece explains the mathematical reason behind A-series paper proportions: a rectangle whose aspect ratio is preserved when bisected repeatedly. Starting from an A0 sheet of area 1 m² and that special ratio, successive halving produces A1, A2, A3 and then A4 with dimensions of 21.0 cm × 29.7 cm. The author then demonstrates the technique in practice by aligning and folding an A4 sheet to estimate the width and height of a turned-off monitor, computing a diagonal, converting centimeters to inches, and concluding the screen was about 27 inches. The tone mixes plain explanation with light humor and explicit cautions that the method is neither fast nor accurate and should not be used for precision work like cabinetry.
Why it matters
- A-series paper sizes are designed so halving a sheet preserves the same aspect ratio, which simplifies scaling and folding.
- A4's fixed dimensions make it a readily available reference for informal, on-the-spot size estimates.
- The example shows how basic geometry and unit conversion can turn an everyday object into a rough measuring aid.
- It underscores that improvised methods can be serviceable for casual checks but are not substitutes for calibrated tools.
Key facts
- A0 paper is defined in the piece as having an area of 1 m² and dimensions approximately 84.1 cm × 118.9 cm.
- Bisecting A0 repeatedly yields A1, A2, A3 and A4; A4 is given as 21.0 cm × 29.7 cm.
- The A-series aspect ratio is chosen so that cutting parallel to the short side produces two smaller sheets with the same aspect ratio.
- Folding an A4 sheet once produces an A5-sized rectangle with dimensions 14.8 cm × 21.0 cm (as used in the demonstration).
- Using lined-up and folded A4 edges, the author estimated the monitor width ~60 cm and height ~34 cm, giving a diagonal near 68.9 cm.
- Converting that diagonal using 1 in = 2.54 cm yields roughly 27.2 inches, matching a 27-inch display estimate.
- The author cautions the method is neither fast nor precise and is not recommended by standards bodies for accurate work.
- The piece was published by Susam Pal on 06 Jan 2026.
What to watch next
- Using A4 for precision tasks (kitchen cabinets, furniture) — not confirmed in the source
- How availability of A4 varies across regions and how that affects ad-hoc measuring — not confirmed in the source
- Whether smartphone measurement apps or other portable tools would have produced a different, more accurate result — not confirmed in the source
Quick glossary
- A4 paper: A common paper size in the A-series with dimensions 21.0 cm × 29.7 cm, widely used for printing and writing.
- Aspect ratio: The ratio of a rectangle's longer side to its shorter side; important for preserving shape when scaling or halving sheets.
- A-series (ISO 216): A family of paper sizes in which each size is half the area of the previous one and shares the same aspect ratio so that halving preserves proportions.
- Diagonal (screen): The length measured from one corner of a rectangular screen to the opposite corner, commonly used to describe display size.
Reader FAQ
Is using A4 paper a reliable way to measure things accurately?
No — the author describes it as neither fast nor accurate and explicitly says it is not recommended for precision work.
What are the exact dimensions of A4 paper?
A4 is 21.0 cm by 29.7 cm, according to the explanation in the piece.
Why do A-series paper sizes preserve shape when halved?
Because they use an aspect ratio chosen so that cutting parallel to the short side yields two rectangles with the same aspect ratio; the author derives this property starting from an A0 sheet of area 1 m².
Did the author confirm the monitor was exactly 27 inches using professional tools?
Not confirmed in the source.
A4 Paper Stories By Susam Pal on 06 Jan 2026 I have a measuring technique that is neither fast, nor accurate, nor recommended by any standards body and yet it…
Sources
- A4 Paper Stories
- How to Measure Things Without a Ruler
- How to determine the size of non-standard printer paper …
- How to Measure Length Without A Ruler: Simple DIY …
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