Welcome to the most accurate and community-trusted **A Bra That Fits Calculator**. This tool utilizes the advanced six-measurement method to provide you with a recommended US/UK bra size, offering a superior starting point compared to traditional +4 sizing methods.
A Bra That Fits Calculator
Recommended US/UK Bra Size:
Detailed Calculation Breakdown
A Bra That Fits Calculator Formula
The A Bra That Fits (ABTF) method is not a single algebraic formula but a systematic approach using multiple measurements to determine band and cup size independently, minimizing guesswork associated with breast shape and projection.
Avg. Bust = (Standing Bust + Leaning Bust + Lying Bust) / 3
Cup Difference = Round(Avg. Bust – Band Size)
Cup Letter = Cup Difference converted using standard US/UK size chart.
Variables
The calculation requires six distinct measurements, all taken in inches (in):
- **Loose Underbust:** Your circumference when breathing normally, for maximum comfort.
- **Snug Underbust:** Your circumference when the tape measure is pulled taut, but not painfully tight. This determines the base band size.
- **Tight Underbust:** Your circumference when exhaling fully and pulling the tape as tight as possible (the “break the tape” measurement). This determines the minimum viable band size.
- **Standing Bust:** Your circumference when standing straight, measuring over the nipples.
- **Leaning Bust:** Your circumference measured while leaning over at a 90-degree angle. This measurement often captures projection better.
- **Lying Bust:** Your circumference measured while lying on your back. This helps average out measurements influenced by gravity.
Related Calculators
What is the A Bra That Fits (ABTF) Method?
The A Bra That Fits methodology revolutionizes bra sizing by moving away from the outdated “add 4 inches” rule, which frequently leads to wearing a band that is too loose and cups that are too small. By taking six specific measurements—three underbust and three bust measurements—the ABTF method calculates a personalized, data-driven starting size recommendation. This comprehensive approach accounts for anatomical variations, tissue migration, and breast projection that a simple two-measurement system misses.
The method operates on the principle that the band size should primarily be determined by the underbust measurements, while the cup size is determined by the difference between the average bust measurement and the calculated band size. The three bust measurements are averaged to mitigate the influence of different breast shapes on a single measurement point, offering a more reliable indicator of overall breast volume.
How to Calculate A Bra That Fits (Example)
Let’s use an example with the following inputs (in inches) to illustrate the calculation:
- Loose Underbust: 32.5 in
- Snug Underbust: 31 in
- Tight Underbust: 30 in
- Standing Bust: 39 in
- Leaning Bust: 40 in
- Lying Bust: 38 in
**Step 1: Determine Band Size (31 in):** The snug underbust (31 in) is rounded up to the nearest even number, giving a band size of **32**.
**Step 2: Calculate Average Bust Size:** ($$(39 + 40 + 38) / 3 = 39$$ in).
**Step 3: Calculate Cup Difference:** The difference is Average Bust minus Band Size ($$39 – 32 = 7$$ in).
**Step 4: Convert Difference to Cup Letter:** A 7-inch difference corresponds to a US size of **G** (7th letter difference: A=1, B=2, C=3, D=4, DD=5, DDD/F=6, G=7).
**Result:** The recommended size is **32G (US)** or **32F (UK)**.
Frequently Asked Questions (FAQ)
Is the ABTF calculator always 100% accurate?
No calculator is 100% accurate, as breast shape (such as root width and projection) significantly affects how a bra fits. The ABTF result provides an excellent starting point and sister size range, but fine-tuning based on shape is usually required.
Why do I need six measurements instead of two?
The six measurements account for the firmness and squishiness of the rib cage (3 underbust measures) and the variation in breast volume under different gravitational pulls (3 bust measures). This triangulation provides a much more precise estimate of your true size.
What is the difference between US and UK sizing?
UK sizing is generally more consistent, especially past a D cup. In UK sizing, the cups progress D, DD, E, F, FF, G, GG, etc. US sizing often uses confusing progressions like D, DD, DDD, G, H, I, etc. The calculator will provide both standard conversions.
My band size feels tight, what should I do?
The Snug and Tight measurements are critical. If the calculated band size feels too tight, try your next “sister size” up (e.g., if you are a 32G, try a 34FF). The tighter band provides necessary support and better lift.