Quick Answer: The classic tailoring rule is ‘sometimes, always, never’ — for a three-button blazer, fasten the middle always, the top sometimes, and never the bottom button. For a two-button blazer, fasten only the top. Leaving the bottom button open isn’t sloppy — it’s actually correct.

Most people either button every blazer button out of habit or leave all of them open, both of which miss a simple tailoring rule that instantly makes a blazer sit better.

What is the actual button rule and why does it exist?

The rule — ‘sometimes, always, never’ — comes from traditional tailoring and exists for a structural reason: blazers are cut with extra room at the bottom hem specifically assuming the bottom button stays open. Fastening the bottom button pulls the fabric tight and creates awkward pulling across the hip, which is why a buttoned bottom often looks stiff or ill-fitting even on a well-tailored piece.

For a two-button blazer, only the top button gets fastened; the second is left open for the same structural reason.

What does this look like in practice for common blazer styles?

On a standard two-button blazer, fasten the top button when standing, and it’s generally fine to unbutton entirely when seated. On a three-button blazer, the middle button is the primary one to keep fastened, the top is optional depending on the cut and your preference, and the bottom always stays open regardless of style.

Single-button blazers follow the simplest version: fasten it when standing, unbutton when sitting, since sitting in any fastened blazer creates pulling across the lap.

Blazer Fit Checkpoints Beyond the Button Rule

Buttoning correctly matters, but it can’t fix an underlying fit issue — shoulder seams should sit exactly at the edge of your natural shoulder, sleeve length should end near the wrist bone, and there should be enough room through the chest to fasten the correct button without pulling. If the correct button still creates strain across the chest, that’s a sizing issue the button rule alone won’t solve.

FAQ: Blazer Button Questions, Answered

Does the button rule apply to casual, unstructured blazers too?

No — the rule matters most for structured, tailored blazers; softer, unstructured styles are more flexible since they weren’t cut with the same hem allowance.

Is it ever acceptable to button all the buttons?

Generally no for tailored pieces — even on formal occasions, fastening the bottom button is considered a fit mistake by traditional tailoring standards, not a formality upgrade.

Should the button rule change based on body type?

The core rule stays the same, but on some fuller-hip proportions, leaving even the second button open on a three-button style can look more flattering than the standard ‘sometimes’ guidance.

TL;DR:

• The rule is sometimes, always, never — top sometimes, middle always, bottom never
• Two-button blazers: fasten only the top
• The bottom button is left open by design, not by mistake
• Correct buttoning can’t fix an underlying shoulder or chest fit issue

A blazer that ‘doesn’t sit right’ is often just being buttoned according to habit instead of according to how it was actually tailored to be worn.