reddit bra calculator
An accurate tool based on the /r/ABraThatFits community method to find your starting bra size.
Measurement Calculator
Enter your six measurements in inches, taken without a bra on. For best results, use a soft measuring tape.
Wrap the tape loosely around your ribcage, right under your bust. The tape should not indent the skin.
Wrap the tape snugly (not tight) around your ribcage at a neutral breath.
Wrap the tape as tightly as possible, after exhaling fully.
Measure around the fullest part of your bust while standing straight.
Lean forward 90 degrees and measure around the fullest part of your bust.
Lie on your back and measure around the fullest part of your bust.
This size is a starting point. Fit can vary by brand and breast shape. The formula uses your snug underbust for the band and the average of three bust measurements to determine cup volume.
Sister Size Chart
Sister sizes are alternative sizes where the cup volume is the same. If your recommended band feels too tight or too loose, you can try a sister size. Go up a band size and down a cup size (e.g., 30F to 32E), or down a band size and up a cup size (e.g., 30F to 28FF).
| Tighter Band | Recommended Size | Looser Band |
|---|---|---|
| 28FF | 30F | 32E |
Measurement Comparison Chart
This chart visually compares your underbust measurements to your bust measurements. A large difference between the three bust measurements can indicate a projected breast shape, which is a key factor in finding a well-fitting bra.
What is the reddit bra calculator?
The reddit bra calculator refers to the sizing method and community-driven calculator popularized by the Reddit forum /r/ABraThatFits. It’s an alternative to outdated sizing methods (like adding 4 inches to the band) that often result in poorly fitting bras. The core principle of the reddit bra calculator is to use precise body measurements to determine a more accurate starting bra size, often leading to a smaller band and larger cup size than what most people are used to wearing.
This method is for anyone who struggles with common bra fit issues like gaping cups, slipping straps, a riding-up band, or painful underwires. By taking six specific measurements, the reddit bra calculator accounts for variations in breast shape and tissue distribution, providing a much more nuanced and personalized recommendation. The “sticker shock” of seeing a size like “28FF” or “34G” is common, but it often reflects a more supportive and comfortable fit than sizes found in traditional department stores.
A common misconception is that cup sizes like DD, F, or G are inherently “huge.” In reality, cup size is relative to the band size. A 30F has a much smaller total volume than a 40F. The reddit bra calculator helps demystify this system and empowers users to understand that good fit is about proportions, not just a letter.
reddit bra calculator Formula and Mathematical Explanation
The logic behind the reddit bra calculator is more detailed than traditional methods. It uses an average of bust measurements to account for shape and calculates cup volume based on the difference between the bust and underbust. The process is as follows:
- Determine Band Size: The band size is typically derived from the snug underbust measurement, often rounded to the nearest even number to provide a firm, supportive base. 90% of a bra’s support comes from the band.
- Determine Average Bust Measurement: The three bust measurements (standing, leaning, and lying) are averaged to create a more accurate representation of breast volume than a single measurement could. `Average Bust = (Standing + Leaning + Lying) / 3`.
- Calculate Cup Volume Difference: The crucial step is finding the difference between the average bust measurement and the loose underbust measurement. `Difference = Average Bust – Loose Underbust`.
- Convert Difference to UK Cup Size: Each inch of difference corresponds to a cup size. The UK system is used for its consistency in larger cup sizes (A=1″, B=2″, C=3″, D=4″, DD=5″, E=6″, F=7″, etc.).
Using this data-driven approach, the reddit bra calculator provides a starting size that is mathematically sound and based on your unique anatomy.
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Loose Underbust | Ribcage measurement, tape held loosely | inches | 26 – 48 |
| Snug Underbust | Ribcage measurement, tape held snugly | inches | 25 – 47 |
| Tight Underbust | Ribcage measurement, tape held very tight | inches | 24 – 46 |
| Standing Bust | Fullest part of bust while standing | inches | 30 – 60 |
| Leaning Bust | Fullest part of bust while bent at 90 degrees | inches | 31 – 65 |
| Lying Bust | Fullest part of bust while on your back | inches | 30 – 62 |
Practical Examples (Real-World Use Cases)
Example 1: Smaller Band, Larger Cup
- Inputs: Loose: 28.5″, Snug: 27.5″, Tight: 26″, Standing: 34″, Leaning: 36″, Lying: 34.5″
- Calculation:
- Band Size: 28 (from 27.5″ snug, rounded)
- Average Bust: (34 + 36 + 34.5) / 3 = 34.83″
- Difference: 34.83″ – 28.5″ = 6.33″
- Cup Size: ~6″ difference is an E cup in UK sizing.
- Output: A starting size of 28E. This is a great example of someone who might be incorrectly sized into a 32B or 32C in a store. The reddit bra calculator correctly identifies the need for a much smaller, more supportive band.
Example 2: Mid-Range Size
- Inputs: Loose: 34″, Snug: 33″, Tight: 31.5″, Standing: 40″, Leaning: 42″, Lying: 40.5″
- Calculation:
- Band Size: 34 (from 33″ snug, rounded)
- Average Bust: (40 + 42 + 40.5) / 3 = 40.83″
- Difference: 40.83″ – 34″ = 6.83″
- Cup Size: ~7″ difference is an F cup in UK sizing.
- Output: A starting size of 34F. This person might be wearing a 36D or 38C and suffering from a band that rides up and cups that overflow. The reddit bra calculator provides a size that will offer significantly better support.
How to Use This reddit bra calculator
- Take Your Measurements: Using a soft measuring tape, take all six measurements as described in the input field helper text. For best results, measure in inches and without any clothing on.
- Enter the Values: Input each of your six measurements into the corresponding field in the calculator above. The calculator will update in real time.
- Analyze the Primary Result: The main result is your recommended starting UK bra size. Remember that this is a starting point, not a final answer.
- Review Intermediate Values: Look at the band size, average bust, and cup difference. These numbers help you understand *how* the calculator arrived at your size.
- Consult the Sister Size Chart: If the recommended band feels too tight or loose when you try on bras, check the sister size chart for alternatives that maintain the same cup volume.
- Consider Your Shape: The numbers are only half the story. Use the article content below to learn about breast shape (projection, fullness, root width) as these factors are critical for finding a bra that not only has the right size but also the right shape for you.
Key Factors That Affect reddit bra calculator Results
While the reddit bra calculator is a powerful tool, several factors beyond the measurements influence your perfect fit:
- Breast Shape (Projection vs. Shallow): Projected breasts stick out more from the chest, while shallow breasts have tissue spread over a wider area. A projected person needs bras with deep cups, while a shallow person needs wider, more open cups, even if their calculator size is the same.
- Breast Fullness (Top vs. Bottom): Whether you have more tissue above or below the nipple affects which bra styles work best. For example, top-full breasts often spill out of plunge bras but do well in full-cup styles.
- Root Width: This refers to how wide the base of your breast tissue is on your chest. A bra’s underwire should match your root width. If the wire is too narrow, it will dig into breast tissue. If it’s too wide, it may poke your armpit.
- Brand and Style Variation: Just like with clothes, bra sizing is not standardized across brands. A 32F from one brand may fit differently than a 32F from another. You may need to adjust your size depending on the brand.
- Tissue Density: Soft, malleable breast tissue can fit into a wider variety of cup shapes than firm, dense tissue, which requires a very specific shape match to avoid gaps or spillage.
- The “Scoop and Swoop” Technique: How you put on your bra is crucial. After fastening the band, you should lean forward and “scoop and swoop” all the breast tissue from under your arms into the cups. This ensures all your tissue is properly contained and is the only way to accurately assess fit.
Ultimately, the best way to use the reddit bra calculator is as the first step on a journey of exploration and learning about your body.
Frequently Asked Questions (FAQ)
- 1. Why is the size from the reddit bra calculator so different from my store-bought size?
- Most stores use outdated “+4” methods, which add 4 inches to the underbust measurement to determine band size. This puts nearly everyone in a band that is too large and a cup that is too small. The reddit bra calculator uses your actual measurements for a snugger, more supportive fit.
- 2. Is a DD/F/G cup size considered large?
- Not necessarily. Cup size is relative to band size. A 30DD is a small-to-medium overall size, whereas a 42DD has much more volume. The reddit bra calculator often reveals that many people are in this range.
- 3. The recommended band size feels too tight. Is it wrong?
- A new, properly fitting band should feel very snug. Try the bra on upside-down and backwards, so the cups are on your back. If the band feels comfortable this way, the tightness is likely because the cups are too small or the wrong shape. If the band still feels too tight, then try a sister size up in the band (and down in the cup).
- 4. What do I do if the cups are gapping?
- Gapping doesn’t always mean the cups are too big; it’s often a shape mismatch. If you have projected breasts and are wearing a shallow, molded T-shirt bra, you will likely have gapping. Try an unlined, seamed bra in your reddit bra calculator size to better diagnose shape issues.
- 5. Can I use this calculator for US sizing?
- The calculator provides a UK size because UK brands are more consistent and widely available in a larger range of sizes. After a UK DD cup, US sizing becomes inconsistent (e.g., DD -> DDD/F -> G). It is recommended to shop using your UK size for better results.
- 6. How often should I re-measure myself?
- It’s a good idea to re-measure every 6-12 months, or after any significant weight change, pregnancy, or starting/stopping hormonal birth control, as these can all affect bra size.
- 7. What is “sister sizing”?
- Sister sizes are a group of bra sizes that have the same cup volume. For example, 32D, 34C, and 36B are sister sizes. The reddit bra calculator helps you find your best starting point, and sister sizes give you options from there.
- 8. Why are there six measurements?
- The three underbust measurements help determine band snugness. The three bust measurements account for how gravity and position affect breast tissue, giving a more accurate average volume than a single standing measurement could. This is a key feature of the reddit bra calculator.
Related Tools and Internal Resources
Once you’ve found your size with the reddit bra calculator, explore these other resources to continue your journey:
- Shallow vs. Projected Guide: Learn to diagnose your breast shape, a critical factor for fit.
- Top & Bottom Fullness Guide: Understand your vertical fullness to choose the right cup styles.
- Recommended Bras for Beginners: A curated list of bras that are great for diagnosing fit when starting out.
- The Scoop and Swoop Tutorial: A visual guide to the most important step in putting on a bra.
- {related_keywords}: Our complete glossary of bra fitting terms.
- {related_keywords}: An index of bra reviews sorted by size.