Bra Size Calculator Reddit

Calculated Band

Average Bust

Bust-Band Difference

Copied!

Your Sister Sizes

These sizes have the same cup volume. If the band feels too tight or too loose in your recommended size, try one of these.

Band Looser / Cup Smaller	Recommended Size	Band Tighter / Cup Larger

What is the bra size calculator reddit Method?

The bra size calculator reddit refers to a specific sizing method popularized by the online community r/ABraThatFits. It stands in stark contrast to older, often inaccurate methods (like adding 4 inches to your band measurement) that many retail stores traditionally used. This calculator uses six precise measurements to get a much more accurate starting point for your true bra size. It acknowledges that breasts are three-dimensional and that their shape and volume can change depending on posture.

This method is for anyone who has struggled with poor-fitting bras—gapping cups, digging straps, or bands that ride up. By providing a more detailed assessment, it empowers users to find sizes they may have never considered, often leading to a dramatic improvement in comfort and support. The core idea is that the band should be snug and supportive, and the cup should fully contain the breast tissue. If you’re new to this, be prepared for “sticker shock”—your calculated size might be a smaller band and a much larger cup than you’re used to!

The Formula and Explanation Behind the Reddit Bra Size Calculator

The logic isn’t one single formula, but a series of steps to determine the band and cup size. The goal is to match the band to your frame and the cup to your breast volume.

1. Band Size: The band size is typically derived from your snug underbust measurement. For most people, rounding the snug measurement up to the nearest even number gives a good starting band size. For example, a snug measurement of 31.2 inches would point to a 32 band.
2. Cup Volume Measurement: This is where the multiple bust measurements come in. The calculator often uses the leaning bust measurement or an average of all three (standing, leaning, lying) as the most accurate representation of breast volume. This is because leaning forward helps capture all the breast tissue, especially for projected shapes.
3. Cup Size Calculation: The cup size is the difference between your bust measurement (step 2) and your band size (e.g., 32). Each inch of difference corresponds to a cup letter.

Variables Table

All measurements should be taken without a bra on. The unit (inches or cm) is selected in the calculator.

Variable	Meaning	Unit	Typical Range
Loose Underbust	Measurement around the ribcage with a loose tape.	in/cm	24 – 50 in
Snug Underbust	A firm measurement around the ribcage, like a new bra band.	in/cm	23 – 48 in
Tight Underbust	Measurement around the ribcage with the tape pulled as tight as possible.	in/cm	22 – 46 in
Standing Bust	Measurement around the fullest part of the bust while standing up.	in/cm	25 – 60 in
Leaning Bust	Measurement around the fullest part of the bust while bent over at 90 degrees.	in/cm	26 – 65 in
Lying Bust	Measurement around the fullest part of the bust while lying down.	in/cm	25 – 62 in

Practical Examples

Example 1: Smaller Band, Average Projection

Let’s look at a user with the following measurements in inches:

• Inputs: Loose: 30″, Snug: 29″, Tight: 28″, Standing: 35″, Leaning: 37″, Lying: 36″
• Calculation:
  • The snug underbust of 29″ points towards a 30 band.
  • The leaning bust of 37″ is used. The difference is 37″ – 30″ = 7″.
  • A 7″ difference is the 7th letter in the alphabet: A, B, C, D, DD, E, F.
• Results: A starting size of 30F (UK) or 30G (US). This is very different from the 34B they might have been wearing from a department store. The bra shape guide is a great next step.

Example 2: Larger Band, Shallow Shape

Let’s look at a user with the following measurements in inches:

• Inputs: Loose: 38.5″, Snug: 38″, Tight: 36″, Standing: 42″, Leaning: 43″, Lying: 42.5″
• Calculation:
  • The snug underbust of 38″ points directly to a 38 band.
  • The bust measurements are very close, suggesting a shallow shape. We’ll use the leaning measurement of 43″. The difference is 43″ – 38″ = 5″.
  • A 5″ difference is the 5th letter: A, B, C, D, DD.
• Results: A starting size of 38DD (UK & US). This user might want to explore our bras for shallow breasts.

How to Use This bra size calculator reddit

Follow these steps to get your most accurate starting size:

1. Select Your Unit: Choose between inches and centimeters. Inches are standard for UK/US sizing.
2. Take Your 6 Measurements: Use a soft measuring tape. For best results, measure yourself without a bra on. Ensure the tape is parallel to the floor for all measurements. Be precise!
3. Enter the Numbers: Input each measurement into the corresponding field. The calculator will update in real-time.
4. Interpret the Results: The calculator will provide a primary UK and US starting size. Remember, this is a starting point, not a final verdict. Use this size as your baseline for trying on bras.
5. Check Sister Sizes: The table shows you sizes with the same cup volume. If a 32E band feels too tight, try its sister size up, a 34DD. If you want a tighter band, try a 30F.

Key Factors That Affect Bra Fit

Your calculated size is just the beginning. Perfect fit is also about shape. Here are key factors to consider:

• 1. Breast Shape (Projection): Are your breasts “projected” (like a cup) or “shallow” (like a plate)? A bra made for a projected shape won’t fit a shallow shape well, even in the “right” size, causing gaps. You may need our projected breast guide.
• 2. Breast Fullness: Are you more full on the top, bottom, or evenly full? This affects what style of cup (e.g., balconette vs. full cup) will work best for you.
• 3. Brand and Style Variations: Just like jeans, bra sizing is not standardized across brands. A 32F in one brand might fit like a 32E in another.
• 4. Sizing System (UK vs. US): UK and US sizing are identical up to a DD cup. After that, they diverge. UK uses FF, G, GG, H, while US often uses F(DDD), G, H, I. Our calculator provides both. This is where a bra size conversion chart comes in handy.
• 5. Sister Sizing: Understanding that a 34D has the same cup volume as a 32DD and 36C is a superpower. It gives you more options when a band doesn’t fit quite right.
• 6. Time and Body Changes: Weight fluctuation, hormonal cycles, and age can all change your breast size and shape. It’s a good idea to remeasure every 6-12 months.

Frequently Asked Questions (FAQ)

1. Why does this calculator use 6 measurements?

The three underbust measurements help determine the best band support, while the three bust measurements account for how breast tissue behaves in different positions, giving a more accurate volume estimate than a single measurement.

2. My calculated size is shocking! Can it be right?

Yes! Most people who have been wearing store-sized bras are in a band that is too large and a cup that is too small. A 36C wearer might find their true size is closer to 32E. Trust the measurements as a starting point and try some bras in your new size. You can also explore a fit check guide to confirm.

3. Is this calculator 100% accurate?

No calculator is perfect. It’s an excellent mathematical starting point, but it cannot account for individual factors like breast shape, root width, or tissue density. Think of it as getting your foot in the door of the right section of the bra store.

4. What are sister sizes?

Sister sizes are bra sizes that have the same cup volume. To find a sister size, you go up in the band and down in the cup (e.g., 34C -> 36B), or down in the band and up in the cup (e.g., 34C -> 32D).

5. What’s the main difference between UK and US sizing?

After DD, the systems diverge. UK sizing continues with double letters (E, F, FF, G, GG, etc.). US sizing typically uses single letters after DD (E/DDD, F, G, H, etc.), but it can be inconsistent. Most brands recommended by the Reddit community use UK sizing.

6. What do I do if I’m between two sizes?

It’s best to try both! You may find one fits better in certain styles or brands. For example, if you’re between a 30E and 30F, a padded plunge style might fit better in the smaller cup, while an unlined balconette fits better in the larger one.

7. How do I know if a bra *really* fits?

The band should be snug and parallel to the floor. The center gore (front part between cups) should lie flat against your sternum. Your breast tissue should be fully contained within the cups with no spilling or gaping. Straps should not be digging in.

8. Where can I even buy bras in sizes like 28G or 34J?

You’ll have the most success shopping online. Websites like Bravissimo, Bare Necessities, and Brastop specialize in a wide range of sizes. Many UK brands like Panache, Freya, and Curvy Kate are popular choices.

Related Tools and Internal Resources

Once you have your starting size, the journey continues! Use these resources to refine your fit.