Fountain Pen Nib Sizes Explained

The nib is the heart of a fountain pen — the shaped metal point that meets the paper and decides how wide, wet, and characterful your line turns out. Nib sizes look simple on a chart, but a few quirks trip up almost everyone new to the hobby, especially the gap between how Western and Japanese makers label the same widths. Here’s what the letters mean and how to predict the line you’ll actually get.

The standard width letters

Most round nibs are sold by a single letter that describes how much line they lay down. From finest to broadest, the common Western sizes run roughly:

• EF (extra fine): around 0.4 mm — a thin, precise line for small handwriting and tight margins.
• F (fine): around 0.5 to 0.6 mm — still crisp, a touch more forgiving than EF.
• M (medium): around 0.7 mm — the balanced all-rounder most pens ship with.
• B (broad): around 0.9 to 1.0 mm — a bold, wet line that shows off ink color and shading.

These are approximate. A nib’s stated size is a starting point, not a precise measurement, because the real line width depends on more than the tipping alone.

The Japanese-versus-Western catch

Here is the single most important thing to know before buying online: Japanese nibs run about one full size finer than their Western equivalents. The major Japanese makers — Pilot, Sailor, and Platinum — grind their points narrower than European houses such as Pelikan, Lamy, and Montblanc. As a rule of thumb:

A Japanese Medium writes roughly like a Western Fine.

So if you love a fine line, a Japanese Fine will be very thin indeed, while a European Medium will feel generous and wet. Ignore this and a pen ordered sight-unseen can land a size or more away from what you pictured. When you’re comparing a Japanese nib against a European one, our nib size converter lines the two systems up so you know what you’re really ordering.

Shaped nibs: stub, italic, and oblique

Not every nib is a plain round point. Shaped nibs deliberately vary the line to add character:

• Stub: a broad, rounded edge that writes thick on downstrokes and thinner on cross-strokes, giving handwriting a gentle calligraphic flair while staying easy to use.
• Italic: like a stub but with sharper, crisper corners — more dramatic line variation, but less forgiving of a careless angle.
• Oblique: a point cut at an angle to suit writers who rotate the pen in the hand, keeping the sweet spot aligned with the paper.

Why the same nib can write differently

Two people can put identical nibs to paper and get noticeably different lines, because tipping size is only part of the equation. Three other factors matter:

• Ink wetness: a free-flowing, wet ink spreads wider than a dry one, effectively bumping your line up a size.
• Paper absorbency: cheap, uncoated paper drinks ink and lets it spread along the fibers, widening the line; coated paper keeps it tight.
• Writing angle and speed: more pressure and a slower hand both let more ink down onto the page.

This is why the same Western Medium can look like a fine line on smooth paper with a dry ink, and a broad one on absorbent paper with a wet ink.

Which size should you pick?

If you write small or your handwriting is compact, lean fine — EF or F in a Western pen, and remember that a Japanese F will be finer still. If you want to enjoy ink shading and sheen, or your hand is larger, a Medium or Broad gives the ink room to show off. For a first fountain pen, a Western Fine or Medium is the safe, versatile choice: wet enough to feel smooth without flooding ordinary paper. From there you can branch into stubs and broads once you know what kind of line makes you want to keep writing.