Straight, fitted or oversized blazer: which fit should you choose?

In short:

1. A blazer fit comes down to chest ease: about 9.5 to 11 cm for a fitted blazer, 11 to 14 cm for a straight one, over 15 cm for an oversized one.
2. In a French size 38 (86 cm bust), that means a jacket about 48 cm flat from armpit to armpit when fitted, 48.5 to 50 cm when straight, 50.5 cm and more when oversized.
3. Length does not decide the fit: two jackets with tailored collars read on 20 October 2026, one slightly fitted, the other slightly oversized, both measured 72 cm from the shoulder in a French size 36.
4. Buttoning (single or double-breasted) and lapels (notched or peak) are separate choices: they do not change the fit.

A women’s oversized blazer, a straight blazer and a fitted blazer differ first in one measurement: the room left between the body and the jacket at the chest. The fitted blazer reduces it and takes it in at the waist with darts. The straight blazer falls without shaping the waist. The oversized blazer adds volume on purpose, with widened or dropped shoulders. Everything else, buttoning, lapels, length, combines with all three fits. Here is how to recognise them on a product page, which body shapes each one suits and what to wear them with.

Fitted, straight or oversized blazer: measurements in one table

The values below are rough guides. Ease comes from the jacket fit chart published by the sewing magazine Threads (issue 221), converted to centimetres. The jacket chest measurements are calculated for a French size 38 (UK 10), starting from an 86 cm bust, the middle of the 82 to 90 cm range given by French size charts. Every brand drafts its own patterns.

One way to read this table: the gap between a fitted and an oversized blazer rarely exceeds 15 cm around the chest. Measured flat, that is 5 to 7 cm. A difference you see at once on the body.

Ease: what makes the fit of a blazer

Ease is the room a garment leaves beyond the body’s measurements. Pattern makers distinguish two kinds, as the encyclopedia entry on ease in sewing explains: wearing ease, which lets you sit and move, and design ease, added to create a silhouette. One source cited by that entry sets wearing ease at 2.5 inches at the bust, about 6.4 cm.

A jacket is worn over other clothes. Its starting ease is therefore larger than a blouse’s. In Louise Cutting’s table published by Threads, a fitted jacket keeps 3¾ to 4¼ inches of ease (9.5 to 10.8 cm), a semifitted jacket 4⅜ to 5⅜ inches (11.1 to 13.7 cm), a loose-fitting jacket 5⅞ to 10 inches (14.9 to 25.4 cm) and a very loose-fitting jacket more. For a fitted blouse, the same table drops to 3 to 4 inches, or 7.6 to 10.2 cm.

These categories do not carry shop names. But they map onto them well: the fitted blazer matches the fitted jacket, the straight blazer the semifitted one, the oversized blazer the last two. That figure, more than the label, tells you whether the blazer will let you slip a sweater underneath.

The fitted blazer: darts to shape the waist

A fitted blazer takes in fabric at the waist with darts, folds sewn to a point that remove ease to give volume to the bust and take it away at the waist. Vertical darts start at the hem and run up towards the bust, according to the definition of a dart in sewing. The result: the jacket follows the curve between bust and hips.

In a French size 38, a fitted blazer measures about 48 cm flat from armpit to armpit. The shoulder seam sits at the end of the shoulder, never beyond it. A fitted blazer in your size closes without pulling: if an X-shaped crease forms around the button, the jacket is too tight.

It is the closest fit to the body, and the most demanding on size. Between two sizes, look at the shoulder width: a shoulder that is too narrow is hard for a tailor to fix, while a waist that is too wide is easy to take in.

The straight blazer: a clean line with no shaped waist

A straight blazer falls from shoulder to hem without nipping in at the waist. It has few darts, or none. The encyclopedia entry on the suit gives a telling example: the American sack suit, cut without darts, has a straighter, looser line than darted jackets.

In a French size 38, a straight jacket is around 48.5 to 50 cm flat, with a shoulder seam that stays at the end of the shoulder. Those few extra centimetres compared with a fitted blazer let a shirt or a fine knit pass underneath without bunching. The jacket does not depend on your waist measurement: only bust and shoulders count.

Watch the vocabulary on product pages. “Straight” describes the cut, not the number of button rows. A jacket read on 20 October 2026 was described at once as an “oversized tailored jacket”, with a “straight cut” and “double-breasted”. The three words describe three different things.

The oversized blazer: volume by design

An oversized blazer adds design ease: over 15 cm around the chest, or 50.5 cm and more flat in a French size 38. That volume sits mostly at the shoulders. Two approaches coexist: wide shoulder pads that extend the shoulder line, or a lowered shoulder seam that falls on the upper arm, which some product pages call a “low shoulder line”.

The wide shoulder has a long history. According to the encyclopedia entry on shoulder pads, Paris couturiers brought them into their collections as early as 1931; by the early 1940s, nearly every garment had them except lingerie. They returned from 1978, then became the sign of 1980s “power dressing”, before shoulders narrowed again late in the decade. Cotton shoulder pads from the 1930s lost their shape in the wash; those of the 1980s were made of foam, sometimes removable thanks to a hook-and-loop strip.

Should you size up to get the oversized effect? No. An oversized blazer is drafted roomy in your own size. One product page read on 20 October 2026 even advised the opposite: take one size down for a closer fit. A classic jacket taken two sizes up mostly lengthens the sleeves and drops the shoulder seam in a random place.

Buttoning and lapels: single, double-breasted, notched or peak

Buttoning is chosen separately from the fit. A single-breasted jacket has one column of buttons, most often two or three; the one-button jacket has regained some popularity, notes the entry on the suit. Convention says you leave the bottom button of a two-button jacket undone, and fasten the middle button of a three-button jacket.

A double-breasted blazer has wide overlapping front panels and two symmetrical columns of buttons. On most current models only one column actually fastens; the other is decorative, and an inner button holds the underlap, according to the entry on double-breasted garments. Tailors write the arrangement as “six-on-two” or “six-on-one”: six buttons in all, two or one fastening. A double-breasted jacket is almost always worn closed. For a short torso, the same entry points to four- or six-button models where only the bottom button fastens.

Lapels follow the buttoning. The entry on lapels lists three kinds:

• the notched lapel, sewn to the collar at an angle that forms a step, standard on single-breasted jackets;
• the peak lapel, the most formal, found on double-breasted jackets and sometimes on single-breasted ones;
• the shawl collar, a single curve, mostly kept for dinner jackets.

Lapel width has changed over the decades. A rule of thumb attributed to one designer in the same entry: the lapel stops slightly short of halfway between the collar and the shoulder line.

Length and sleeves: what product pages show

The length of a blazer is measured from the highest point of the shoulder down to the hem. On women’s jacket pages read on 20 October 2026 from French ready-to-wear brands, in a French size 36:

• a structured jacket with a tailored collar, “slightly fitted at the waist”, measured 72 cm;
• a “slightly oversized” suit jacket also measured 72 cm;
• a wool jacket measured 71.5 cm;
• a short structured jacket stopped at 51 cm, a boxy jacket at 55 cm in size S.

The lesson is simple: length does not tell you the fit. A classic tailored jacket covers the hips, around 72 cm in a French size 36, whether fitted or roomy. Cropped jackets, around 51 to 55 cm, fall at the waist and pair mainly with high-waisted bottoms.

For sleeves, one fitting rule is enough: with your arms by your sides, the sleeve covers the wrist bone. On an oversized blazer, rolled-up sleeves are part of the look; they then sit at mid-forearm.

Which blazer fit for which body shape

Body shape does not dictate everything, but a few pointers help:

• Defined waist, hips and shoulders about equal: the fitted blazer follows that line. A straight blazer hides it without fighting it.
• Hips wider than shoulders: a straight blazer that covers the hips, or an oversized one with structured shoulders, balances top and bottom.
• Shoulders wider than hips: go for a natural shoulder, without thick pads, in a straight or slightly fitted cut. A narrow notched lapel lightens the top.
• Straight figure: all three fits work. The fitted blazer creates a waist, the oversized one plays on contrast.
• Petite: a cropped or standard length, and a moderate oversize rather than a jacket that reaches mid-thigh. Single-breasted buttoning lengthens the figure better than a six-button double-breasted front.
• Tall: check sleeve length and total length on the product page, because a jacket that is too short loses its balance.

Our view, plainly: if you only buy one blazer, make it a straight, single-breasted one. It takes a shirt as well as a fine sweater, closes without pulling, and looks just as right open as closed.

What to wear with each fit

The basic rule fits in one sentence: volume on top calls for a cleaner line below, and the other way round.

• Fitted blazer: it balances a wide leg. With wide-leg or palazzo trousers, the defined waist of the jacket keeps the silhouette readable. It also works over straight jeans or a pencil skirt.
• Straight blazer: the easiest fit to pair. Straight trousers, jeans, a midi dress or a velvet dress for the festive season, and in winter a fine sweater underneath: a fine-knit turtleneck slips under a jacket without bulk.
• Oversized blazer: slim bottoms or a short dress, so the figure does not drown. With a loose shirt underneath, keep a single oversized piece; our guide on what size to get for an oversized shirt helps balance the volumes.

A practical point for winter: an oversized blazer under a coat needs a coat with ease of its own. Before ordering one, our guide to choosing your women’s coat size explains which measurements to compare.

How to measure a blazer before ordering

Size charts give body measurements, and the ISO 8559-1 standard sets how to take them (bust, waist, hips). The fit, however, shows in the garment’s measurements. To compare a product page with what you already own, lay a blazer that fits you well flat, buttoned, and note:

1. Shoulder width: from one shoulder seam to the other, across the back.
2. Chest width: from armpit to armpit, across the front, jacket closed. Double it to get the circumference.
3. Length: from the highest point of the shoulder to the hem, at the front, or from the collar to the hem at the back, depending on the product page.
4. Sleeve length: from the shoulder seam to the edge of the sleeve.

Then compare your jacket’s chest width with half your own bust measurement: the gap tells you whether you like to wear things fitted, straight or roomy. And if you order from a UK or US site, the women’s size conversion chart for France, the UK and the US keeps you in the right column.

From rowing club to women’s wardrobe

The word “blazer” first meant the bright red flannel jackets worn by the rowers of the Lady Margaret Boat Club, the rowing club of St John’s College, Cambridge, founded in 1825. The London Daily News gave that definition on 22 August 1889, according to the encyclopedia entry on the blazer. The jacket lost its sporting ties in the 1930s. Double-breasted jackets went through two great spells of popularity: from the mid-1930s to the late 1950s, then from the mid-1980s to the early 2000s.

Today’s three fits all descend from that sports jacket. To choose between them, keep one figure in mind: about 10 cm of chest ease for a fitted blazer, 12 for a straight one, 15 and more for an oversized one.