How to Measure Your Bra Size at Home

You can measure your bra size at home with just a soft measuring tape and a mirror. Measure your underbust to estimate your band size, then measure around the fullest part of your bust. Use these measurements together with the sizing method of the brand you’re buying from to find your starting bra size.

The important word here is starting. Bra sizing isn’t perfectly standardized across every brand or style, so your measurements should guide you towards the right size rather than be treated as an absolute rule.

Why Knowing Your Bra Size Matters

A bra can be beautifully made and still feel uncomfortable if the size isn’t right.

A band that’s too loose may ride up your back. Cups that are too small can cause spillage, while cups that are too large may gape. Straps may also slip or dig into your shoulders when the overall fit isn’t right.

The good news is that you don’t necessarily need a professional fitting to get a useful starting point. You can take your measurements at home in a few minutes.

What You’ll Need

• A soft measuring tape
• A mirror
• A non-padded, lightly structured bra or no bra
• A pen and paper or your phone to record the measurements

Avoid measuring over thick clothing or a heavily padded bra because it can change the bust measurement.

Stand naturally rather than deliberately expanding your chest or holding your stomach in.

Step 1: Measure Your Underbust

Your underbust is the circumference of your ribcage directly underneath your breasts.

Stand in front of a mirror and wrap the measuring tape around your ribcage, immediately below your bust where your bra band would normally sit.

Make sure the tape is:

• Level around your body
• Snug, but not painfully tight
• Flat against your skin
• Not twisted at the back

Take the measurement in inches and write it down.

How Does This Become Your Band Size?

This is where bra sizing can become confusing.

Foma Innerwear uses a legacy manufacturing sizing method in which the band size includes a comfort allowance. For example, an underbust measurement of 30 inches corresponds to a 34 band using this method.

Other brands may use different sizing systems, which is why the same body measurements can sometimes produce different recommended sizes.

If you’re shopping for Foma bras, use our Bra Size Guide & Size Calculator to convert your measurements into the size used for our bras.

Step 2: Measure Your Bust

Next, measure your overbust or bust circumference.

Wrap the measuring tape around the fullest part of your breasts.

Check yourself in the mirror and make sure the tape runs horizontally around your body.

The tape should rest gently against your body. Don’t pull it so tightly that it compresses your breasts, but don’t leave it hanging loose either.

Write down this measurement.

Now you have the two measurements needed to estimate your bra size:

Step 3: Find Your Band Size

Use your underbust measurement with the size chart provided by the bra brand you’re considering.

This step matters because bra sizing isn’t completely uniform between brands.

A measurement that points towards one size on one company’s chart may point towards a slightly different size elsewhere.

Step 4: Find Your Cup Size

Cup size is determined by the relationship between your bust and band measurements rather than by your bust measurement alone.

Under Foma’s sizing method, cup size is calculated using the difference between your overbust measurement and calculated band size.

For example, using Foma’s sizing method:

You can skip doing this calculation manually by using the Foma Bra Size Calculator .

Your Bra Size Is More Than a Number

Suppose two women both wear a B cup. That doesn’t mean their cups are the same size.

A 32B and 38B are not equivalent bras because cup volume changes along with band size.

That’s one reason saying “I’m a B cup” doesn’t provide your complete bra size.

Step 5: Try the Bra and Check the Actual Fit

Measurements narrow down your options. The bra itself tells you whether you’ve found the right fit.

1. Check the Band

The band should sit relatively level around your body rather than climbing significantly up your back.

It should feel secure without making it difficult to breathe comfortably.

A new bra is generally best assessed on its loosest comfortable hook so you have room to adjust the band as the elastic changes with wear.

2. Check the Cups

Your breasts should sit comfortably inside the cups.

Cup may be too small if:

• Breast tissue spills over the top or sides
• The cup edge noticeably cuts into the breast
• You feel compressed inside the cup

Cup may be too large if:

• There’s empty space inside the cup
• The fabric wrinkles or gapes
• The cup doesn’t sit against the breast properly

3. Check the Straps

The straps shouldn’t constantly fall off your shoulders, but they also shouldn’t need to be tightened so much that they dig deeply into your skin.

The band provides an important part of a bra’s support, so overtightening the straps shouldn’t be the solution to a loose band.

4. Move Around

Don’t judge the fit while standing perfectly still. Try:

• Raising your arms
• Sitting down
• Bending slightly
• Moving your shoulders
• Walking around

The bra should stay reasonably secure and comfortable as you move.

Common Mistakes When Measuring Bra Size at Home

Pulling the Measuring Tape Too Tightly

Your underbust measurement should be snug, but don’t pull the tape aggressively into your skin. Likewise, don’t compress your breasts while taking the bust measurement.

Letting the Tape Slope

Use a mirror to check the tape. If it’s much higher or lower at the back than the front, your measurement can change.

Measuring Over a Padded Bra

Padding adds volume and can affect your bust measurement. Measure without a bra or while wearing a thin, non-padded bra.

Assuming Your Old Size Must Still Fit

Bodies change. Weight changes, hormonal changes, pregnancy, ageing and other factors can affect breast and body measurements.

Re-measuring occasionally is therefore useful, particularly when your existing bras suddenly stop feeling comfortable.

Assuming Every Brand Fits Identically

Even if you’ve comfortably worn one size for years, don’t automatically assume that size will fit exactly the same across every brand and every bra style.

Check the brand’s size chart before ordering.

What If You’re Between Two Sizes?

Don’t panic if your measurements don’t land neatly on a size chart. Bodies aren’t manufactured in standardized increments.

Start with the size closest to your measurements and assess the actual fit.

You may also encounter sister sizes. Sister sizes use a different band and cup combination while maintaining approximately similar cup volume.

For example, moving up one band size usually means moving down one cup size to maintain a similar cup volume, while moving down a band generally means moving up a cup.

Signs You Should Recheck Your Bra Size

• Your band repeatedly rides upward
• Your breasts spill out of the cups
• Your cups consistently gape
• Your straps constantly fall down despite adjustment
• Your bra feels significantly tighter than before
• Your body measurements have changed
• You haven’t measured yourself for a long time
• You’re repeatedly uncomfortable in your current bras

Your bra size isn’t something you need to remain loyal to.

Comfort and fit matter more than the number printed on the label.

Quick Bra Measurement Checklist

Keep your measurements saved on your phone. It makes comparing size charts much easier the next time you shop.

Frequently Asked Questions

Can I measure my bra size at home?

Yes. A soft measuring tape can give you useful underbust and bust measurements at home. Use those measurements with the size chart of the brand you’re considering and then assess how the actual bra fits.

Should I wear a bra while measuring?

You can measure without a bra or in a thin, non-padded bra. Avoid heavily padded or push-up bras because they can affect your bust measurement.

How tight should the measuring tape be?

For the underbust, keep it snug and level without pulling painfully into your skin. When measuring your bust, let the tape rest gently around the fullest part without compressing your breasts.

Is bra size the same for every brand?

Not necessarily. Sizing methods, construction and fit can differ between manufacturers and styles. That’s why you should check the specific brand’s sizing information before purchasing.

How do I know whether my bra fits correctly?

Look at the complete fit rather than only the label. The band should remain relatively level and secure, your breasts should sit comfortably inside the cups without significant spillage or gaping, and the straps shouldn’t constantly slip or painfully dig into your shoulders.

Why does my usual bra size sometimes not fit?

Different bra designs can sit differently on the body, and brands don’t necessarily use identical sizing and construction. Your body measurements can also change over time.

How often should I measure my bra size?

There’s no universal schedule you have to follow. Re-measure when your existing bras stop fitting comfortably, after meaningful body changes, or whenever you’re unsure about your current size.

The Most Important Rule: Fit Comes Before the Label

Learning how to measure your bra size at home gives you a much better starting point for shopping, particularly when buying bras online.

But don’t become too attached to a particular number or cup letter.

That’s a more reliable approach than assuming one calculated bra size will fit every bra you buy.

Ultimately, the right bra is the one that feels comfortable and fits your body well.