Thirdlove Bra Size Calculator
An expert tool for discovering your accurate bra size based on the ThirdLove fitting method. Achieve the perfect balance of comfort and support with our precise calculator.
Measurement Inputs
Measure snugly around your ribcage, directly under your bust. The tape should be level.
Please enter a valid positive number.
Measure around the fullest part of your bust. Keep the tape level and not too tight.
Please enter a valid positive number.
Your Calculated Bra Size
32C
Calculated Band Size
32
Calculated Cup Size
C
Bust-Band Difference
3.5″
Your cup size is determined by the difference between your bust and underbust measurements. We use half-inch increments for a more precise fit, a hallmark of the ThirdLove approach.
| Your Sister Size Chart | ||
|---|---|---|
| Go Down a Band Size | Your Calculated Size | Go Up a Band Size |
| 30D | 32C | 34B |
What is a Thirdlove Bra Size Calculator?
A Thirdlove bra size calculator is a specialized online tool designed to determine your most accurate bra size based on specific body measurements. Unlike generic calculators, the Thirdlove bra size calculator incorporates the brand’s unique fitting philosophy, which often includes half-cup sizes to provide a more precise and comfortable fit. It helps bridge the gap between standard sizing and individual body shapes, addressing common fit issues like gaping cups, slipping straps, and tight bands.
This calculator should be used by anyone struggling to find a comfortable, well-fitting bra. If you’ve experienced weight fluctuations, pregnancy, or simply feel your current bra is no longer serving you, using a Thirdlove bra size calculator is an excellent first step. A common misconception is that your bra size remains the same for years. In reality, your body changes, and so does your ideal bra size. Regularly using a tool like the Thirdlove bra size calculator ensures you adapt to these changes.
Thirdlove Bra Size Calculator Formula and Explanation
The core logic of the Thirdlove bra size calculator revolves around two key measurements: the underbust (for the band size) and the fullest bust (for the cup size). The process is broken down into simple steps.
- Determine Band Size: The band size is derived from the underbust measurement. The raw measurement (in inches) is rounded up to the next even number. For example, a 31.5-inch measurement results in a 32 band size.
- Calculate Measurement Difference: Subtract the underbust measurement (not the final band size) from the bust measurement. This difference is crucial for determining the cup volume.
- Determine Cup Size: The difference calculated in the previous step corresponds to a letter, which may include half sizes. For example, a 3-inch difference is a C cup, while a 3.5-inch difference is a C½ cup. This nuanced approach is central to the Thirdlove bra size calculator.
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Underbust Measurement | The circumference of the ribcage directly below the breasts. | Inches | 26 – 48 |
| Bust Measurement | The circumference over the fullest part of the bust. | Inches | 28 – 56 |
| Measurement Difference | Bust Measurement – Underbust Measurement | Inches | 0.5 – 10 |
| Calculated Band Size | The final band size number. | Size (e.g., 32, 34) | 28 – 50 |
| Calculated Cup Size | The final cup size letter. | Letter (e.g., C, C½) | AA – H |
Practical Examples
Example 1: Standard Sizing
- Inputs: Underbust = 33 inches, Bust = 37 inches.
- Calculation:
- Band Size: 33 inches rounds up to a 34 band.
- Difference: 37″ – 33″ = 4 inches.
- Cup Size: A 4-inch difference corresponds to a D cup.
- Output: The Thirdlove bra size calculator recommends a 34D. This person likely needs a standard size with good support.
Example 2: Half-Cup Sizing
- Inputs: Underbust = 29.5 inches, Bust = 33 inches.
- Calculation:
- Band Size: 29.5 inches rounds up to a 30 band.
- Difference: 33″ – 29.5″ = 3.5 inches.
- Cup Size: A 3.5-inch difference corresponds to a C½ cup.
- Output: The Thirdlove bra size calculator suggests a 30C½. This highlights the importance of half-cups for someone who finds a C cup too small but a D cup too large. It’s a perfect example of how to find my bra size with greater precision.
How to Use This Thirdlove Bra Size Calculator
- Enter Underbust Measurement: Use a soft measuring tape to measure your ribcage. Enter this value in the first input field. Ensure the tape is snug but not constricting.
- Enter Bust Measurement: Measure around the fullest part of your bust. Enter this value in the second input field.
- Review the Results: The calculator will instantly display your calculated bra size, including your band and cup size. Pay attention to the primary result.
- Check Intermediate Values: Look at the “Bust-Band Difference” to understand how your cup size was determined.
- Explore Your Sister Sizes: The Sister Size Chart shows alternative sizes with the same cup volume. This is useful if your recommended size is out of stock or if you want a looser or tighter band. Our guide on the correct bra fit can provide more context.
Key Factors That Affect Thirdlove Bra Size Calculator Results
- Measurement Accuracy: The most critical factor. An inaccurate measurement, even by half an inch, can change the result. Always measure twice.
- Time of Month: Hormonal fluctuations can cause breasts to swell. It’s best to measure at a time in your cycle when your breasts are at their baseline size.
- Type of Bra Worn During Measurement: For the most accurate bust measurement, wear a non-padded, lightly lined bra. Measuring without a bra can sometimes lead to an inaccurate bust measurement if your breasts are not supported.
- Posture: Stand up straight when measuring. Slouching can alter both your underbust and bust measurements.
- Breast Shape: Breast shape (e.g., shallow, projected, asymmetric) can affect how a bra fits, even if the size is technically correct. The Thirdlove bra size calculator gives a great starting point, but you might need a specific style for your shape. A ThirdLove fit finder can help with this.
- Band Elasticity: Over time, a bra’s band will stretch out. A new bra should fit snugly on the loosest hook, so be sure your current bra’s fit isn’t skewing your perception.
Frequently Asked Questions (FAQ)
- 1. How often should I use a thirdlove bra size calculator?
- It’s recommended to remeasure yourself every 6-12 months, or after significant life events like pregnancy, weight loss/gain, or starting a new fitness regimen.
- 2. What if I’m between two band sizes?
- The calculator automatically rounds up. However, if you prefer a very snug fit, you could try the sister size with a smaller band and larger cup. See our sister size calculator for more options.
- 3. Are half-cup sizes really necessary?
- For many, they are a game-changer. If you constantly have slight gaping or spillage, a half-cup provides the micro-adjustment needed for a perfect fit, which is a core part of the ThirdLove sizing philosophy.
- 4. Does the calculator work for all bra brands?
- This calculator is optimized for ThirdLove’s sizing. While it provides a very reliable starting point for any brand, sizing can vary. Always check a brand’s specific size chart.
- 5. What does “sister size” mean?
- Sister sizes are alternate sizes where the cup volume is the same. For example, a 34C has the same cup volume as a 32D and a 36B. Knowing this is helpful for finding a better fit.
- 6. My two breasts are different sizes. How do I measure?
- Always fit to the larger breast. You can use a small insert or “cookie” in the cup for the smaller breast to create a symmetrical appearance if desired.
- 7. Why does this calculator not add 4 inches to the band (the “+4 method”)?
- The “+4 method” is an outdated technique from when bras were made with less elastic materials. Modern bras are designed to fit snugly based on your true underbust measurement, providing better support. The Thirdlove bra size calculator uses this modern approach.
- 8. Can I find my sports bra size with this calculator?
- This calculator provides your standard bra size. While it’s a good starting point, sports bras often use different sizing (e.g., S/M/L) and have different fit requirements based on impact level. It is best to consult a specific sports bra size chart.