US Letter paper Size in Inches & cm

US Letter paper is 8.5 x 11 inches, or 215.9 x 279.4 mm. It is the default office and home-printer size across the United States, Canada, and parts of Latin America, while most of the rest of the world uses the slightly different A4.

This guide covers the exact Letter dimensions, how it compares to A4 and to US Legal, why the two systems never merged, and how a sheet sizes up against a laptop, a clipboard, and a manila folder.

Quick Answer: How Big Is US Letter Paper?

US Letter is 215.9 x 279.4 mm (8.5 x 11 in). A single 20 lb (75 gsm) sheet weighs about 4.5 grams. It is 6 mm wider and 18 mm shorter than A4.

US Letter Dimensions at a Glance

• Size: 215.9 x 279.4 mm / 21.59 x 27.94 cm / 8.5 x 11 in
• vs A4 (210 x 297 mm): Letter is 5.9 mm wider, 17.6 mm shorter
• Aspect ratio: 1:1.294 (A4 is 1:1.414, so Letter is squarer)
• Common weights: 20 lb bond / 75 gsm (4.5 g), 24 lb / 90 gsm (5.4 g), 32 lb / 120 gsm (7.2 g), 65 lb cover / 176 gsm (10.6 g)

What Does US Letter Paper Look Like in Size?

A sheet of Letter paper is the footprint of a standard clipboard, a manila folder (unfolded it is a bit larger), and roughly the deck area of a 15-inch laptop with a little to spare. Held upright it runs from a desktop to about elbow height when you rest your forearm on the desk.

6 Everyday Comparisons for US Letter Paper

1. A4 paper (210 x 297 mm) is narrower and taller. Stack the two and Letter overhangs on the sides while A4 overhangs at the top.
2. US Legal paper (215.9 x 355.6 mm) is the same width but 76 mm (3 in) longer.
3. A 15-inch laptop (about 340 x 240 mm closed) is a little wider and shorter than a Letter sheet.
4. A standard clipboard is built around exactly this size.
5. A vinyl record sleeve (315 x 315 mm) is wider and squarer.
6. A cereal box front is roughly two-thirds of a Letter sheet.

US Letter Size in Different Units

Why the US Uses Letter Instead of A4

A4 comes from ISO 216, built on the 1:root 2 ratio so sizes halve cleanly. US Letter predates that system and comes from a different tradition, reportedly tied to the dimensions a person could comfortably stretch and cut by hand, later fixed by manufacturers and the US government. Because printers, folders, envelopes (the No. 10 envelope fits a Letter sheet folded in thirds), filing cabinets, and software defaults were all built around 8.5 x 11, switching would touch almost every office object in North America. So the two standards coexist, and most software lets you pick either.

Common Mistakes When Comparing US Letter Paper

1. Assuming Letter and A4 are interchangeable. They differ enough that a full-bleed A4 design gets clipped on Letter, and a Letter design leaves a margin on A4.
2. Calling Letter “8×11”. It is 8.5 x 11 inches.
3. Confusing Letter with Legal. Same width, but Legal is 3 inches longer.
4. Mixing paper-weight systems. US “20 lb bond” and metric “75 gsm” describe the same everyday copy paper.
5. Using 72 DPI for print pixels. Letter at 300 DPI is 2550 x 3300 px.

Frequently Asked Questions

How big is US Letter paper in mm?

215.9 x 279.4 mm.

How big is Letter paper in cm?

21.59 x 27.94 cm.

Is US Letter the same as A4?

No. Letter is 5.9 mm wider and 17.6 mm shorter than A4.

Is Letter the same as Legal?

No. Legal is the same width but 76 mm (3 in) longer.

How much does a sheet of Letter paper weigh?

About 4.5 g for standard 20 lb / 75 gsm copy paper.

Why does the US not use A4?

Letter predates the ISO system and is baked into North American printers, envelopes, folders, and filing, so both standards coexist.

What DPI is Letter at print resolution?

2550 x 3300 pixels at 300 DPI.

Final Takeaway

US Letter paper is 215.9 x 279.4 mm (8.5 x 11 in) and weighs about 4.5 grams per standard sheet. It is wider and shorter than A4, the same width as but 3 inches shorter than Legal, and it stays the North American default because so much office equipment is built around it.