Fountain Pen Nib Sizes Explained: EF, F, M, B, and Stub
Nib size is the single most consequential choice when buying a fountain pen, more than the brand, the color, or even the price, and it's also the one most first-time buyers get wrong simply because the labels (EF, F, M, B, and the rest) aren't explained anywhere obvious at the point of purchase.
What nib size actually controls
Nib size determines line width, not writing pressure. Fountain pens are meant to glide, never press, regardless of nib size. A wider nib simply lays down a wider line and, generally, more ink per stroke, which affects how colors shade and sheen and how quickly ink dries on the page.
The standard sizes, in order
Extra-fine (EF) produces the thinnest line, suited to small, dense handwriting and thinner paper, though it shows less ink character (shading, sheen) than broader sizes. Fine (F) is the most commonly recommended default for a first pen: noticeably finer than most ballpoints, but forgiving and versatile. Medium (M) is a genuinely different writing experience from F, wider and wetter, showing more of what an interesting ink can do, and it's a common second-nib choice. Broad (B) and wider sizes favor bold, expressive strokes and show off shading and sheen most dramatically, at the cost of being less practical for small or dense writing.
Stub and italic sizes
Beyond the standard round sizes, stub and cursive italic nibs are ground with a flatter tip that produces line variation (thick downstrokes, thin crossstrokes) similar to calligraphy, without requiring calligraphy technique. These are a distinct category from EF through B and worth a separate look once you already know you enjoy the hobby; see our guide to custom nib grinds for more detail.
How brands differ
The same letter doesn't always mean the same width across brands. Japanese nibs (Pilot, Sailor, Platinum) tend to run a size or so finer than their labeled European or American equivalent, so a Japanese fine often writes closer to a European extra-fine. This is worth knowing before assuming a size based on a single brand's chart.
Picking a first nib size
For a genuine first fountain pen, a fine (F) is the safest, most broadly recommended starting point: forgiving on ordinary paper, suited to most handwriting sizes, and easy to build a feel for before branching into wider or specialty grinds later.