Fit Calculator Bra

Find your perfect bra size with our easy-to-use calculator. Accurate measurements lead to ultimate comfort and support.

Your Recommended Bra Fit

Key Assumptions

Bra Style—

Underbust Measurement— cm

Overbust Measurement— cm

How it's Calculated:

The band size is typically your underbust measurement. The cup size is determined by the difference between your overbust and underbust measurements. Different bra styles may require slight adjustments.

Bra Fit Measurement Guide

Measurement Difference (cm)	US Cup Size	UK Cup Size	EU Cup Size
0-1.5	AA	AA	A
1.5-3	A	A	B
3-5	B	B	C
5-7	C	C	D
7-9	D	D	E
9-11	DD/E	DD	F
11-13	DDD/F	E	G
13-15	G	F	H
15-17	H	FF	I
17-19	I	G	J
19-21	J	GG	K
21-23	K	H	L

Finding the right bra size is crucial for comfort, support, and overall well-being. This comprehensive guide, featuring our advanced bra fit calculator, demystifies the process, helping you achieve a perfect fit every time.

What is a Bra Fit Calculator?

A bra fit calculator is an online tool designed to help individuals determine their most accurate bra size based on a few key body measurements. Unlike traditional methods that rely solely on guesswork or outdated sizing charts, a bra fit calculator uses specific formulas and considers variations in bra styles and international sizing standards to provide a personalized recommendation.

Who Should Use It: Anyone looking for a more comfortable and supportive bra, experiencing discomfort or poor fit with their current bras, undergoing body changes (weight fluctuations, pregnancy, post-surgery), or shopping for bras online. It's particularly useful for those who find standard sizing confusing or inconsistent across brands.

Common Misconceptions:

• "My size never changes": Body shape and size can fluctuate, meaning your bra size might too.
• "All brands use the same sizing": Bra sizing can vary significantly between brands and even styles within the same brand.
• "The calculator is always 100% accurate": While highly accurate, personal preference and specific bra construction can influence the ideal fit. It's a starting point, not an absolute decree.
• "A tight band means a smaller size": Often, a band that feels too tight indicates the cups are too small, forcing the band forward.

Bra Fit Calculation: Formula and Mathematical Explanation

The core of a bra fit calculator relies on two primary measurements: the underbust (band size) and the overbust (bust size). The difference between these measurements determines the cup size.

Band Size Calculation:

The band size is generally determined by the underbust measurement. While some calculators add a small increment, the most straightforward approach is to use the measurement directly or round to the nearest standard band size (e.g., 32, 34, 36 inches or 70, 75, 80 cm).

Formula: Band Size = Underbust Measurement (adjusted for standard sizing)

Cup Size Calculation:

The cup size is derived from the difference between the overbust and underbust measurements. This difference indicates the volume of the breast relative to the ribcage.

Formula: Cup Size = (Overbust Measurement – Underbust Measurement)

This difference is then mapped to a standard cup size (e.g., A, B, C, D, etc.) based on established sizing charts, which can vary slightly by region (US, UK, EU).

Style Adjustments:

Different bra styles offer varying levels of coverage and support. For example:

• Full Cup/Standard: Generally designed for maximum coverage and support, often aligning closely with calculated sizes.
• Balconette/Demi: Offers less coverage, potentially requiring a slightly different fit or size for optimal appearance.
• Plunge: Features a low center gore, ideal for deep necklines. The fit might feel different due to the cut.
• T-Shirt: Smooth, seamless cups designed for a smooth silhouette under clothing.

Our calculator uses these differences to provide a more nuanced recommendation, though personal comfort remains paramount.

Variables Table:

Variable	Meaning	Unit	Typical Range
Underbust Measurement	Circumference around the ribcage directly below the bust.	cm / inches	60 – 120 cm (approx. 24 – 47 inches)
Overbust Measurement	Circumference around the fullest part of the bust, typically over the nipples.	cm / inches	70 – 140 cm (approx. 28 – 55 inches)
Measurement Difference	The difference between Overbust and Underbust measurements.	cm / inches	0 – 50 cm (approx. 0 – 20 inches)
Band Size	The circumference of the bra band.	cm / inches / Standard Size (e.g., 34, 75)	65 – 110 cm (approx. 30 – 44 inches)
Cup Size	Represents the volume of the breast relative to the band size.	Letter (e.g., A, B, C) / Standard Size	AA to K+
Bra Style	The type or cut of the bra.	Category (e.g., Full Cup, Plunge)	N/A

Practical Examples (Real-World Use Cases)

Example 1: Standard Fit Scenario

Inputs:

• Underbust Measurement: 78 cm
• Overbust Measurement: 95 cm
• Bra Style: Standard/Full Cup

Calculation:

• Band Size: Rounded to the nearest standard size, likely 75 cm (or 34 inches).
• Measurement Difference: 95 cm – 78 cm = 17 cm.
• Cup Size: A difference of 17 cm typically corresponds to a UK G cup, US H cup, or EU I cup.

Calculator Output: Band Size: 75, Cup Size: H (US) / G (UK) / I (EU)

Interpretation: This individual likely needs a bra in the 75H (US) / 75G (UK) / 75I (EU) range. The standard cup style should provide good coverage and support.

Example 2: Plunge Bra Consideration

Inputs:

• Underbust Measurement: 70 cm
• Overbust Measurement: 88 cm
• Bra Style: Plunge

Calculation:

• Band Size: 70 cm (or 32 inches).
• Measurement Difference: 88 cm – 70 cm = 18 cm.
• Cup Size: A difference of 18 cm typically corresponds to a UK GG cup, US I cup, or EU J cup.

Calculator Output: Band Size: 70, Cup Size: I (US) / GG (UK) / J (EU)

Interpretation: For a plunge bra, the calculated size is 70I (US) / 70GG (UK) / 70J (EU). While the calculation provides a starting point, the lower center gore of a plunge bra might feel different. It's advisable to try this size, but be mindful of how the cups sit and if the center gore lays flat against the sternum.

How to Use This Bra Fit Calculator

Using our bra fit calculator is simple and takes just a few minutes. Follow these steps for an accurate assessment:

1. Measure Your Underbust: Place a soft measuring tape snugly around your ribcage, directly under your bust. Ensure the tape is level and not digging in. Record this measurement in centimeters (cm). This is your 'Underbust Measurement'.
2. Measure Your Overbust: Measure around the fullest part of your bust, usually over the nipples. Keep the tape measure parallel to the ground and ensure it's not too tight or too loose. Record this measurement in centimeters (cm). This is your 'Overbust Measurement'.
3. Select Bra Style: Choose the type of bra you are interested in fitting (e.g., Standard, Balconette, Plunge, T-shirt). This helps refine the recommendation.
4. Enter Measurements: Input your recorded underbust and overbust measurements into the respective fields in the calculator.
5. Calculate: Click the "Calculate My Size" button.

How to Read Results: The calculator will display your recommended Band Size (e.g., 75, 80) and Cup Size (e.g., C, D, DD). It will also show the EU equivalent sizes and the key measurements used. The primary result highlights the most likely size combination.

Decision-Making Guidance: Use the calculated size as your primary guide when shopping. Remember that fit can vary by brand and style. If you are between sizes, consider trying the next band size up if the cups feel too small, or the next cup size up if the band feels too tight but the cups fit well. Always prioritize comfort and proper support – the band should be snug and parallel to the floor, the cups should contain the breast tissue without gaping or spilling, and the center gore should ideally sit flat against your sternum.

Key Factors That Affect Bra Fit Results

While our calculator provides a strong starting point, several factors can influence the perfect bra fit:

1. Body Shape and Breast Tissue Density: Different breast shapes (e.g., teardrop, conical, round) and tissue density (soft vs. firm) interact differently with bra designs. A calculator provides a general size, but the specific cut and construction of the bra matter.
2. Bra Construction and Brand Variations: As mentioned, sizing is not universal. A 34D in one brand might fit like a 32DD in another. Seam placement, wire width, and fabric stretch all play a role.
3. Underwire Fit: The underwire should comfortably encase the breast tissue and lie flat against the ribcage, extending towards the armpit. If the wire digs in, pokes, or doesn't reach the armpit, the band or cup size might be incorrect, or the bra style isn't suitable.
4. Band Support: The bra band provides about 80% of the support. It should feel snug and secure, allowing only one or two fingers to fit underneath. If the band rides up your back, it's likely too loose.
5. Strap Adjustment and Comfort: Straps should stay in place without digging into your shoulders. They provide about 10-20% of the support. Overly tight straps can cause discomfort and shoulder pain, while loose straps lead to poor support.
6. Center Gore Placement: The center panel (gore) between the cups should ideally lie flat against your sternum. If it floats away from the body, it can indicate that the cups are too small or the band is too large.
7. Personal Comfort and Preference: Ultimately, the best bra is the one that feels most comfortable and provides the desired support and aesthetic for your needs. The calculator's recommendation is a guide, not a rigid rule.

Frequently Asked Questions (FAQ)

What if my underbust and overbust measurements are very close?

If the difference is small (0-2 cm), you likely need an AA or A cup. Ensure your underbust measurement is accurate and snug.

What if my overbust measurement is significantly larger than my underbust?

This indicates a larger cup size. The calculator will help determine this based on the difference. For very large differences, ensure you are measuring correctly and consider bras designed for fuller busts.

Does the calculator account for international sizing differences?

Yes, our calculator provides US, UK, and EU cup size equivalents where applicable, helping you navigate different sizing systems.

My current bra size doesn't match the calculator result. What should I do?

It's common! Many people wear the wrong bra size. Trust the calculator's recommendation as a starting point and try bras in that size. Your current bra might be ill-fitting or stretched out.

How often should I check my bra size?

It's recommended to check your bra size at least once a year, or whenever you notice significant changes in your body weight, hormonal status (like pregnancy or menopause), or if your current bras feel uncomfortable or ill-fitting.

Can I use this calculator if I'm pregnant or breastfeeding?

While the calculator can provide a starting point, pregnancy and breastfeeding cause significant breast size fluctuations. It's best to measure frequently during these times and consult with a professional fitter if possible. Maternity or nursing bras often require a different fit.

What does the 'Band Size' mean in relation to my underbust measurement?

The band size is the circumference of the bra band. While it's closely related to your underbust measurement, standard band sizes (like 32, 34, 75, 80) are used. Our calculator helps determine the closest standard band size.

How do I know if the underwire is fitting correctly?

The underwire should sit smoothly against your ribcage, encasing all breast tissue, and extend towards your armpit. It should not dig into your breast tissue or poke your skin. If it does, the cup size or bra style might be incorrect.