How to Choose Your Shapewear: The Complete Sizing Guide

November 27, 2025

Comment Choisir son Body Gainant : Le Guide Complet des Tailles

The €60 Mistake 67% of Buyers Make

You fell in love with a shaping bodysuit after reading all the glowing reviews. It arrives, you excitedly try it on, and... disaster. Too tight, it creates unflattering bulges. Too loose, no sculpting effect. The result: 67% of shaping bodysuit returns are due to choosing the wrong size.

This costly mistake is, however, completely avoidable. The problem? Size charts vary enormously from one brand to another, and your usual clothing size does not always correspond to that of a shaping bodysuit.

In this comprehensive guide, you'll discover how to choose the perfect size for your shaping bodysuit according to your body shape, how to measure your body correctly, understand the differences between brands, and most importantly: avoid mistakes that ruin the desired effect.

No more returns, disappointments, and wasted money. It's time for informed choices.

Why Size is CRUCIAL for a Shaping Bodysuit

The Direct Impact on Effectiveness

Unlike a classic garment where a slight sizing error goes unnoticed, an ill-fitting shaping bodysuit completely ruins its effectiveness:

Too small:

Creates multiple bulges (above, below, on the sides)
Excessively compresses, causing extreme discomfort
Constantly rolls up and rides up
Difficult or even impossible to put on
Painfully marks the skin
Impairs blood circulation (dangerous)

Too large:

No effective compression
Slips and sags during the day
No tummy-flattening effect
Visible folds and creases under clothes
Completely wasted investment

Testimonial - Sandrine, 34: "I took my usual size 38. Monumental mistake. Couldn't breathe, bulges everywhere. I reordered a 40 TwinsWomen with their sizing advice, and it's perfect: effective but comfortable compression."

The Absolute Golden Rule

NEVER size down thinking you'll get more compression. This is the fatal mistake made by 43% of disappointed buyers.

Compressive fabric naturally does its job when it's the right size. Forcing a smaller size creates the opposite of the desired effect: you'll appear bulkier with all those artificially created bulges.

The real rule: If in doubt between two sizes, ALWAYS choose the larger size. You can adjust with the straps if necessary.

How to Take Your Measurements Correctly

Required Materials

femme qui se mesure pour porter un body gainant

Essential:

A flexible, non-elastic tailor's measuring tape
A mirror (to check the horizontality of the tape)
Ideally, someone to help you (more accurate)

To avoid:

Rigid construction measuring tape (inaccurate)
Smartphone apps (too many approximations)
Measuring over thick clothes

The 5 Essential Measurements

1. Bust Measurement

Position: Place the tape at the fullest part of your bust, wrap it all the way around, passing under your arms and across your shoulder blades.

Criteria for correct measurement:

Tape measure is horizontal (check in mirror)
Neither too tight nor too loose (should glide easily)
Measure at the end of a natural exhalation (not empty lungs)
Wear your usual bra

Common mistake: Measuring bare-chested and then choosing a size when you'll be wearing a bra underneath (2-5 cm difference).

2. Waist Measurement

Position: Place the tape at the narrowest part of your waist, usually 2-3 cm above your belly button.

Criteria for correct measurement:

DO NOT suck in your stomach (natural measurement)
Relaxed standing position
Tape measure is horizontal
Do not pull the tape tight (just lay it on)

Pro tip: Lean slightly to the side: the crease that forms naturally indicates your waist.

3. Hip Measurement

Position: Measure at the fullest part of your hips/buttocks, usually 18-22 cm below the waist.

Criteria for correct measurement:

Feet together (gap changes the measurement)
Include the most prominent part of your buttocks
Tape measure is horizontal (check from behind in mirror)

Common mistake: Measuring too high (iliac crest level) = 3-7 cm underestimation.

4. Thigh Measurement (If Mid-Thigh Bodysuit)

Position: Measure at the fullest part of your thigh, usually 5-8 cm below the crotch.

Criteria for correct measurement:

Relaxed leg, weight evenly distributed
Tape measure horizontal all around
Do not pull tight (compression will be provided by the bodysuit)

5. Torso Length (Less Common)

Position: From the tip of the shoulder to the crotch, passing over the bust.

Usefulness: Some brands offer short/standard/long sizes. Crucial if you are very petite (under 1.60m) or tall (over 1.75m).

Measurement Chart to Fill In

Measurement	Value (cm)	Notes
Bust	_____ cm	With bra
Waist	_____ cm	Narrowest point
Hips	_____ cm	Fullest point
Thigh	_____ cm	If mid-thigh bodysuit
Torso length	_____ cm	Shoulder-crotch

Keep these measurements: they are valid for 3-6 months (unless significant weight changes).

Understanding Size Charts by Brand

Why Each Brand Differs

European vs. American sizes:

A French size 40 = US size 12 = Italian size 44
American brands (Spanx, SKIMS) sometimes use US sizing
Always check the origin of the size chart

Compression standards:

Strong compression brands (Spanx, Leonisa) generally run smaller
Comfort brands (Yummie, Maidenform) run larger
French brands (TwinsWomen) follow classic European standards

Size Charts for Major Brands

TwinsWomen (Standard French Sizes)

Size	Bust	Waist	Hips
34 (XS)	74-78 cm	58-62 cm	84-88 cm
36 (S)	78-82 cm	62-66 cm	88-92 cm
38 (S/M)	82-86 cm	66-70 cm	92-96 cm
40 (M)	86-90 cm	70-74 cm	96-100 cm
42 (M/L)	90-94 cm	74-78 cm	100-104 cm
44 (L)	94-98 cm	78-82 cm	104-108 cm
46 (XL)	98-103 cm	82-87 cm	108-113 cm
48 (XXL)	103-108 cm	87-92 cm	113-118 cm
50 (3XL)	108-114 cm	92-98 cm	118-124 cm
52 (4XL)	114-120 cm	98-104 cm	124-130 cm

TwinsWomen's Special Feature: True inclusivity up to size 52, French cut adapted to European body types.

→ See detailed TwinsWomen size guide

Spanx (US/International Sizes)

Size	FR Equivalent	Bust	Waist	Hips
XS	34-36	81-86 cm	63-68 cm	89-94 cm
S	36-38	86-91 cm	68-73 cm	94-99 cm
M	38-40	91-97 cm	73-79 cm	99-105 cm
L	42-44	97-104 cm	79-86 cm	105-112 cm
XL	46-48	104-112 cm	86-94 cm	112-120 cm

Spanx's Special Feature: Generally runs smaller than French standard. Size up if in doubt.

Maidenform (Standard US Sizes)

Size	FR Equivalent	Bust	Waist	Hips
S	36-38	84-89 cm	66-71 cm	91-96 cm
M	38-40	89-94 cm	71-76 cm	96-102 cm
L	42-44	94-102 cm	76-84 cm	102-109 cm
XL	46-48	102-109 cm	84-91 cm	109-117 cm
XXL	50-52	109-119 cm	91-102 cm	117-127 cm

Maidenform's Special Feature: Generous sizing, comfort is a priority. Size close to French standard.

SKIMS (US/Inclusive Sizes)

Size	FR Equivalent	Bust	Waist	Hips
XXS	32-34	76-81 cm	58-63 cm	84-89 cm
XS	34-36	81-86 cm	63-68 cm	89-94 cm
S	36-38	86-91 cm	68-73 cm	94-99 cm
M	38-40	91-97 cm	73-79 cm	99-105 cm
L	42-44	97-104 cm	79-86 cm	105-112 cm
XL	46-48	104-112 cm	86-94 cm	112-120 cm
2XL	50-52	112-122 cm	94-104 cm	120-130 cm

SKIMS' Special Feature: Very detailed sizing system, if between two sizes, choose the larger one.

Body Shape Guide

A-Shape (Pear): Hips > Shoulders

Characteristics:

Hips and thighs wider than bust
Defined waist
Narrow shoulders

Sizing rule:

Choose based on your hips (widest measurement)
Accept that the top might be slightly loose
Prioritize adjustable straps to compensate

Recommended styles:

TwinsWomen (adaptive fit)
Mid-thigh bodysuits to smooth hips/thighs

Testimonial - Lucie, 29: "I'm a 38 on top, 42 on the bottom. I took a TwinsWomen size 42 as advised. The top adjusts with straps, the bottom is perfect. Finally, a bodysuit that fits!"

V-Shape (Inverted Triangle): Shoulders > Hips

Characteristics:

Broad shoulders and bust
Narrow hips
Slender legs

Sizing rule:

Choose based on bust and back (upper measurements)
The bottom will be slightly loose, which is normal
Avoid excessive compression at the top

Recommended styles:

Moderate compression (not strong)
Bodysuits with adjustable cups

H-Shape (Rectangle): Shoulders ≈ Hips

Characteristics:

Straight silhouette
Undefined waist
Balanced proportions

Sizing rule:

Easiest to fit!
Follow standard chart
Most brands generally work

Recommended styles:

TwinsWomen, Maidenform (standard sizes)
Any compression level depending on preference

X-Shape (Hourglass): Shoulders ≈ Hips, Defined Waist

Characteristics:

Naturally very defined waist
Shoulders and hips aligned
Harmonious curves

Sizing rule:

Be careful not to over-compress the waist
Choose hip measurement if in doubt
Prioritize gradual compression

Recommended styles:

Bodysuits that enhance natural waist
Avoid overly strong compression (waist already defined)

O-Shape (Round): Prominent Belly

Characteristics:

Volume concentrated in the abdomen
Undefined waist
Main objective: flat stomach

Sizing rule:

CRUCIAL: DO NOT size down
Measure hips AND waist (take the larger measurement)
Prioritize plus-size brands

Recommended styles:

TwinsWomen (up to 52, adapted compression)
Maidenform (up to 52, comfort)
Moderate to strong compression depending on tolerance

Testimonial - Nathalie, 46: "Size 48, I long believed shapewear wasn't for me. TwinsWomen truly offers size 48, not stretched-out 44! Effective compression without suffocating me."

If you prefer shapewear without a crotch, the shaping jumpsuit offers the same support from bust to thighs, with more freedom of movement. For discreet daily wear, the shaping tank top wears like a simple shaping top.

Special Cases and Situations

You Are Between Two Sizes

Situation: Your measurements correspond to two different sizes depending on the area.

Solution:

ALWAYS choose the larger size
Use adjustable straps to compensate
Prefer brands with detailed sizing (TwinsWomen, SKIMS)

Example: Waist = 76 cm (corresponds to 42), hips = 96 cm (corresponds to 38) → Choose 42 (the largest measurement takes precedence)

You Are Petite (Under 5'3")

Problem: Standard bodysuits are too long, crotch too low, straps too long.

Solutions:

Look for "petite" or "short" sizes if available
SKIMS offers petite-friendly sizing
TwinsWomen: ultra-adjustable straps
Check total product length (technical info)

You Are Tall (Over 5'9")

Problem: Bodysuits are too short, compress poorly, pull on shoulders.

Solutions:

Look for "tall" or "long" sizes
Opt for mid-length rather than short bodysuits
Spanx and Triumph offer long options
Check bust height in descriptions

You Have a Large Bust (D-Cup+)

Problem: Integrated cups are unsuitable, excessive breast compression.

Solutions:

Check cup compatibility (up to what cup size?)
Triumph specializes in large busts (up to F)
Opt for open-bust bodysuits if very generous (G+)
Size primarily according to bust measurement

Post-Pregnancy (Body in Transition)

Problem: Fluctuating measurements, skin sensitivity, temporary body shape.

Solutions:

Wait for medical clearance (minimum 6-8 weeks)
Take current size, not pre-pregnancy size
Light compression only
Anticipate body changes (sizing up is wise)
TwinsWomen and Yummie are suitable for postpartum

Testimonial - Emilie, 32: "3 months postpartum, I hesitated between my old size 38 and my current 40. I chose a size 40 TwinsWomen light compression. Perfect, comfortable, and it still fits me now that I've lost weight."

Fatal Mistakes to Absolutely Avoid

Mistake No. 1: Taking Your Clothing Size (58%)

The trap: "I wear a size 40 dress, so a size 40 bodysuit"

Why it's wrong: Clothing sizes vary greatly depending on brands and cuts. A shapewear bodysuit requires precise measurements, not approximate equivalence.

Solution: Measure yourself systematically, consult the brand's specific size chart.

Mistake No. 2: Taking One Size Down (43%)

The trap: "The tighter it is, the more it compresses, so size down"

Why it's wrong: Creates multiple bulges, extreme discomfort, inverse effect. Compressive fabric works best at the correct size.

Solution: Respect your measurements. When in doubt, size up.

Mistake No. 3: Measuring Over Thick Clothing (34%)

The trap: Measuring yourself in thick jeans and a sweater out of laziness

Why it's wrong: Adds 3-7 cm artificially, skews all measurements.

Solution: Measure yourself in thin underwear only.

Mistake No. 4: Not Checking the Chart's Origin (29%)

The trap: Using a French conversion without checking if the chart is US/UK/EU

Why it's wrong: Significant differences between systems (e.g., 40 FR ≠ 40 IT).

Solution: Always check the chart's system (FR/EU/US/UK).

Mistake No. 5: Ignoring Body Shape (24%)

The trap: "The chart says 38, so I'll take 38" even though hips are size 42

Why it's wrong: A disproportionate body requires adjustment.

Solution: Take size according to your WIDEST measurement.

Mistake No. 6: Choosing by Weight Rather Than Measurements (19%)

The trap: "I weigh 65 kg, so I'll take M"

Why it's wrong: Two women weighing 65 kg can be a size 38 and 44 depending on weight distribution/muscle mass/height.

Solution: Only measurements matter, never weight.

Final Pre-Purchase Checklist

Before Ordering

☑️ I have taken my precise measurements (bust, waist, hips, thighs if needed)

☑️ I have consulted THE specific brand's size chart (not a generic one)

☑️ I have identified if it's FR/EU/US/UK sizing

☑️ I have chosen based on my LARGEST measurement if between sizes

☑️ I have NOT sized down from my actual measurements

☑️ I have checked reviews on sizing (runs small/large/true to size?)

☑️ I have consulted the return policy (just in case)

☑️ I have noted my measurements for future purchases

Upon Receipt

☑️ I try it on at home first (not directly for an event)

☑️ I wear it for a 2-3 hour test to check real comfort

☑️ I check for the absence of artificial bulges

☑️ I test it under the snug clothing I plan to wear it with

☑️ I check that it doesn't roll up during movements

☑️ If in doubt, I exchange it (do not keep a poorly sized bodysuit)

Customer Service and Sizing Assistance

TwinsWomen: Personalized Support

Advantages of French service:

Personalized size advice via chat/email
Response within 24 hours (business days)
Free exchange if wrong size
Video guide for taking measurements
30-day satisfaction or money-back guarantee

→ Contact TwinsWomen customer service

Testimonial - Valérie, 41: "I hesitated between 44 and 46. I contacted TwinsWomen customer service with my measurements. They advised me to take 46. Perfect, exactly the right size. Truly excellent service."

Other Brand Services

Spanx: Interactive online sizing guide (English) Maidenform: USA customer service (longer delays) SKIMS: Online body shape quiz Triumph: In-store fitting available

Frequently Asked Sizing Questions

How do I know if my shapewear bodysuit is too small?

Obvious signs:

Bulges above and below
Painful red marks on skin
Difficulty breathing
Constantly rolls up
Impossible to put on alone

→ Exchange immediately for the next size up

How do I know if my shapewear bodysuit is too big?

Obvious signs:

No compression felt
Slips and sags during the day
Fabric folds and wrinkles
Straps at maximum adjustment are still too long
No tummy-flattening effect

→ Exchange for the next size down (the only case where sizing down is acceptable)

What if I'm exactly between two sizes?

ALWAYS choose the larger size. You can adjust with straps, but it's impossible to "create" more fabric if it's too small.

Do TwinsWomen sizes correspond to classic French sizes?

Yes, TwinsWomen follows French/European standards. If you wear a 40 at Zara/H&M, you will probably wear a 40 TwinsWomen. But measure yourself to confirm.

Can I trust "runs small/large" reviews?

With caution. Every body shape is unique. Someone who finds it "runs small" may have taken a size down from their actual measurements. Rely on size charts, not subjective impressions.