X-height

X-height is the height of the main body of a lowercase letter, measured from the baseline to the top of a letter like x, o or n, without counting the parts that stick up or down on letters like l, h, g or y. It is one of the core proportions used to design a consistent alphabet, since every lowercase letter is built to align with the same x-height even though ascenders and descenders vary.

In broad edge calligraphy, x-height and other proportions are traditionally measured in nib widths rather than a fixed unit, so a wider nib produces a bigger x-height at the same number of nib-width units. In pointed pen and modern calligraphy, x-height is usually set directly on a guide sheet instead, since there is no single nib width to measure against.

Getting x-height consistent across a line of lettering is one of the most common struggles for beginners, since even small drift makes a page look uneven. Using a guide sheet or a slant and height calculator helps enforce consistency while the habit is still forming. A frequent mistake is letting x-height creep larger or smaller across a page as fatigue sets in, which is why short, focused practice sessions tend to produce more even results than long unguided ones.