Rectangle and Diamond faces are among the pairs most commonly confused with each other, usually because one or two measurements land close together even though the overall proportions differ.
Rectangle Face Shape
Rectangle: Face length is noticeably greater than width (often 1.7x or more); forehead, cheek, and jaw widths are similar. Also called oblong, this shape shares the square's consistent width from forehead to jaw but stretches significantly longer, often with a tall forehead and elongated cheeks. The jaw can be squared or slightly rounded, but the defining trait is verticality rather than angularity.
Diamond Face Shape
Diamond: Cheekbones are the clear widest point; forehead and jaw are both notably narrower and close in width to each other. A diamond face narrows at both the forehead and the jaw while flaring dramatically at the cheekbones — the opposite structure of a rectangle. The chin is often pointed, and the temples can appear slightly recessed relative to the cheekbone's width.
The Key Difference
The key difference: A rectangle face has a jaw that "squared or gently rounded, similar in width to the forehead," while a diamond face's jaw "narrow, tapering to match the forehead's width." That single measurement — jaw width relative to forehead and cheekbones — is usually the fastest way to tell the two apart when they're otherwise close.
Why It Matters for Styling
Why it matters for styling: Rectangle faces are best served by introduce visual width and interrupt the vertical line — horizontal volume at the sides, fringe or bangs that shorten the forehead, and frames or hairlines with a strong horizontal emphasis all work against excess length rather than adding to it, while diamond faces need soften and add visual width at the forehead and jaw to bring them closer to the cheekbone's width, while avoiding extra volume directly at cheekbone height, which is already the face's widest point — confirming which category you actually fall into before choosing a cut, frame, or beard style matters, since the two shapes' styling advice can point in different directions.