ThirdLove Bra Size Calculator
Find Your Perfect ThirdLove Fit
Follow the steps below to find your recommended bra size. For best results, use a soft measuring tape and measure while wearing a non-padded bra.
What is a ThirdLove Bra Size Calculator?
A thirdlove bra size calculator is a specialized tool designed to determine your most accurate bra size based on ThirdLove’s unique sizing system, which notably includes half-cup sizes. Unlike generic calculators, the thirdlove bra size calculator accounts for the specific fit and design of their bras, providing a more precise recommendation. Anyone who has struggled with cups that gap, bands that dig in, or simply feels their current bra isn’t a perfect fit should use this calculator. A common misconception is that a bra size from one brand will fit the same at another; however, using a brand-specific tool like the thirdlove bra size calculator is essential for finding true comfort and support.
ThirdLove Bra Size Calculator Formula and Mathematical Explanation
The logic behind the thirdlove bra size calculator involves two key measurements: the underbust (for the band) and the fullest part of the bust (for the cup). The process is a simple, two-step calculation.
- Band Size Calculation: The underbust measurement is rounded to the nearest whole number. Then, 3 inches are added if the number is odd, and 2 inches are added if it’s even. This result is your final band size. ThirdLove’s method aims to provide a firm, supportive band.
- Cup Size Calculation: The final calculated band size is subtracted from the bust measurement. The resulting difference in inches corresponds to a specific cup size, including the innovative half-cups that set ThirdLove apart. For instance, a 2.5-inch difference results in a B½ cup.
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Underbust Measurement | Measurement around the ribcage directly under the bust. | Inches | 28 – 45 |
| Bust Measurement | Measurement around the fullest part of the bust. | Inches | 30 – 55 |
| Bust-Band Difference | Bust Measurement – Calculated Band Size | Inches | 0 – 9 |
Practical Examples (Real-World Use Cases)
Example 1: Finding a Half-Cup Size
- Inputs:
- Underbust Measurement: 31.5 inches
- Bust Measurement: 36 inches
- Calculation:
- Band: 31.5 rounds to 32 (even), so 32 + 2 = 34. Your band size is 34.
- Cup: 36″ (Bust) – 34″ (Band) = 2.5″ difference.
- Result: The 2.5″ difference corresponds to a C½ cup. The recommended size from the thirdlove bra size calculator is 34C½.
Example 2: A Standard Cup Size
- Inputs:
- Underbust Measurement: 33 inches
- Bust Measurement: 39 inches
- Calculation:
- Band: 33 (odd), so 33 + 3 = 36. Your band size is 36.
- Cup: 39″ (Bust) – 36″ (Band) = 3″ difference.
- Result: The 3″ difference corresponds to a D cup. The final size is 36D. Using a thirdlove bra size calculator ensures this maps correctly to their styles.
How to Use This ThirdLove Bra Size Calculator
- Enter Your Band Measurement: Using a soft tape measure, find the length around your ribcage, just under your bust. Enter this number (in inches) into the first input field.
- Enter Your Bust Measurement: Measure loosely around the fullest part of your chest. Enter this number into the second field.
- Read Your Results: The calculator will instantly update. The primary result is your recommended ThirdLove bra size. You will also see your calculated band size, cup size, and the measurement difference.
- Consult the Sister Size Chart: The table below the result shows your sister sizes. If your recommended size’s band feels too tight, try the size with a larger band and smaller cup. This feature makes our thirdlove bra size calculator a comprehensive bra fitting guide.
Key Factors That Affect ThirdLove Bra Size Results
Finding the perfect fit with a thirdlove bra size calculator is the first step, but several factors can influence how a bra actually fits your body.
- Breast Shape: Are your breasts teardrop, east-west, or round? Shape affects how you fill a cup. ThirdLove’s Perfect Coverage bras are great for fuller shapes, while plunge styles often suit less full or east-west shapes.
- Band Snugness: The band should provide ~80% of the support. It should be snug and parallel to the floor. If it rides up, you need a smaller band size.
- Cup Spillage or Gaping: If you spill out of the top or sides (quad-boob), you need a larger cup size. If the cups are puckered or have gaps, try a smaller cup or a half-cup size.
- Gore Tacking: The center part of the bra (the gore) should lie flat against your sternum. If it sits away from your chest, your cups are likely too small.
- Strap Tension: Straps should only provide about 20% of the support. If they dig into your shoulders, your band is probably too loose. They shouldn’t be falling off, either.
- Time and Body Changes: Your body changes over time due to weight fluctuations, hormones, and age. It’s wise to re-measure yourself and use a thirdlove bra size calculator every 6-12 months.
Frequently Asked Questions (FAQ)
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. If your band fits but your cup doesn’t (or vice versa), they are your best tool for adjustment. Our thirdlove bra size calculator provides these automatically.
Bra sizing is not standardized across the industry. ThirdLove’s inclusion of half-cup sizes and their specific fit model means your ideal size with them might be different. That’s why a dedicated thirdlove fit finder is more accurate.
If you’re in between, consider your preference. Do you like a very snug fit or a slightly looser one? A good rule is to start with the smaller band size, as bras stretch over time. You can use the loosest hook at first and move inwards.
It’s recommended to measure yourself every 6 to 12 months, or after any significant life changes such as pregnancy, weight loss, or weight gain, to ensure you’re always wearing the best fit.
This is a classic sign that your band is too large and not providing enough support. You should go down a band size and up a cup size (e.g., from 36C to 34D) to maintain cup volume. A proper thirdlove bra size calculator will show you this sister size.
Gapping usually means the cups are too big. This is a perfect scenario to try a half-size down (e.g., from a C cup to a B½). It could also be a shape mismatch. A different style like a plunge bra might fit better. See our guide to the best T-Shirt bras.
This calculator is optimized for ThirdLove’s sizing. While it can give you a good starting point, the most accurate size for another brand would come from their own calculator or fit guide.
Both are equally important. Your size (band and cup) provides the dimensions, but your breast shape determines how you fill the cup. This is why a size that seems correct on paper might not fit perfectly in certain bra styles.