physics

Letter (paper size)

Letter (paper size) is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Letter (paper size) rather than just read about it. In short: Letter (officially ANSI A) is a paper size standard defined in ANSI/ASME Y14.1 by the American National Standards Institute, commonly used as home or office stationery primarily in the United States, Canada, and the Philippines, and variably across Latin America. It measures 8.5 by 11 inches (215.9 by 279.4 mm) and is similar in use to the A4 paper standard at 210 mm × 297 mm (8.27 in × 11.7 in) used by most other c…

Key takeaways

Letter (paper size) belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Letter (paper size) to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Letter (paper size) from memory before moving on to harder problems.

Reference excerpt

Letter (officially ANSI A) is a paper size standard defined in ANSI/ASME Y14.1 by the American National Standards Institute, commonly used as home or office stationery primarily in the United States, Canada, and the Philippines, and variably across Latin America. It measures 8.5 by 11 inches (215.9 by 279.4 mm) and is similar in use to the A4 paper standard at 210 mm × 297 mm (8.27 in × 11.7 in) used by most other countries, defined in ISO 216 by the International Organization for Standardization.

Details The Reagan administration made Letter-size paper the norm for US federal forms in the early 1980s; previously, the smaller "official" Government Letter size, 8 by 10.5 inches (203.2 by 266.7 mm) (aspect ratio: 1.3125), was used in government, while 8.5-by-11-inch (215.9 by 279.4 mm) paper was standard in most other offices. The aspect ratio is ⁠22/17⁠ ≈ 1.294 and the diagonal is √8.52 + 112 ≈ 13.901 inches (353.1 mm) in length. In the US, paper density is usually measured in "pounds per ream" (of 500 sheets). Typical Letter paper has a basis weight of paper of 20 or 24 pounds (9.1 or 10.9 kg) – the weight of 500 sheets (a ream) of 17-by-22-inch (431.8 by 558.8 mm) paper at 70 °F (21 °C) and at 50% humidity. One ream of 20-pound Letter-sized paper weighs 5 pounds (2.3 kg), and a single Letter-sized sheet of 20-pound paper weighs 0.16 ounces (4.536 g), which is equivalent to 75.19 g/m2. Some metric information is typically included on American ream packaging. For example, 20-pound paper is also labeled as 75 g/m2. The most common density of A4 paper is 80 g/m2. The related paper size known as Invoice (colloquially Half Letter) is exactly one half of the US Letter size: 8.5 by 5.5 inches (215.9 by 139.7 mm).

History

The precise origins of the dimensions of US letter-size paper (8.5 × 11 in) are unknown. The American Forest & Paper Association says that the standard US dimensions have their origin in the days of manual papermaking, with the 11-inch length of the standard paper being about a quarter of "the average maximum stretch of an experienced vatman's arms". The letter size falls within the range of the historical quarto size, which since pre-modern times refers to page sizes of 8 to 9 inches (200 to 230 mm) wide and 10 to 11 inches (250 to 280 mm) high, and it is indeed almost exactly one quarter of the old Imperial (British) paper size known as demy quarto – 17+1⁄2 by 22+1⁄2 inches (444.5 by 571.5 mm) – allowing one-half inch (12.7 mm) for trimming.

See also ANSI/ASME Y14.1 ISO 216 Loose paper sizes PC LOAD LETTER

References

Illustrations

Worked examples

Example 1 — a first encounter with Letter (paper size)

Start with the simplest possible case. Write down what Letter (paper size) claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Letter (paper size) before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Letter (paper size) ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Letter (paper size)

In research: Letter (paper size) appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Letter (paper size) in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Letter (paper size) is common in secondary-school and first-year university syllabi. It links to neighbouring topics Mechanical standards, Paper, Printing, so understanding it makes those chapters shorter.
In everyday life: Look for Letter (paper size) outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Letter (paper size)” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Letter (paper size) in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Letter (paper size) means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Letter (paper size) out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Letter (paper size) in simple terms?

Why does Letter (paper size) matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Letter (paper size)?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Letter (paper size).