The **Reddit Bra Calculator** (often referred to as the **r/ABraThatFits Calculator**) uses a comprehensive set of six measurements to provide an accurate starting point for UK bra sizing, moving beyond the traditional “+4” method. Enter your measurements below to find your recommended size.
Reddit Bra Size Calculator (UK Sizing)
Your Suggested UK Bra Size is:
32FF(This is a starting point. Fit is key!)
Reddit Bra Size Calculator Formula (r/ABTF)
Band Size (B):
B = Round up Snug Underbust (SU) to the nearest even number (min 30).
Average Bust (AB):
AB = (Standing Bust + Leaning Bust + Lying Bust) / 3
Cup Difference (CD):
CD = AB – B
Cup Letter: Mapped from CD (1″ = A, 2″ = B, 5″ = DD, 8″ = FF, etc.)
Formula Sources: r/ABraThatFits Beginners’ Guide, ABraThatFits External Calculator.
Variables Explained
- Loose Underbust: Measured loosely, where the bra band normally sits. Used as a comfort check.
- Snug Underbust: Measured firmly, but not painful. This is the base for your band size.
- Tight Underbust: Measured as tightly as possible, exhaling all air. This is the absolute minimum band size you can tolerate.
- Standing Bust: Measured while standing upright, across the fullest part of the bust.
- Leaning Bust: Measured while leaning over 90 degrees. Captures tissue fullness and projection.
- Lying Bust: Measured while lying flat on your back. Helps determine breast firmness.
What is the Reddit Bra Size Calculator?
The Reddit Bra Calculator, popularized by the r/ABraThatFits subreddit, is widely considered one of the most accurate methods for determining a starting bra size. Unlike traditional retail methods that often add 4 or more inches to the underbust (which leads to loose bands and small cups), this method uses your *actual* snug underbust measurement for the band size.
Furthermore, it incorporates the average of three different bust measurements (standing, leaning, and lying) to account for various breast shapes, projection, and tissue density. This 3D approach averages out potential variations, resulting in a cup size estimate that is far more reliable than single-measurement methods, dramatically increasing the chance of a good fit.
How to Calculate Your Size (Example)
Using a sample measurement set (LU: 32.5, SU: 31, TU: 30, SB: 38, LB: 40, LyB: 39):
- Determine Band Size: The Snug Underbust is 31 inches. Rounding up to the nearest even number gives a band size of 32.
- Calculate Average Bust: ($$ (38 + 40 + 39) / 3 = 117 / 3 = 39 $$ inches).
- Find the Cup Difference: Average Bust minus Band Size ($$ 39 – 32 = 7 $$ inches).
- Map to Cup Letter: A difference of 7 inches corresponds to a **32F** in standard UK sizing (1=A, 5=DD, 7=F).
- Final Suggested Size: 32F.
Related Calculators & Guides
- Bra Sister Size Finder
- Scoop and Swoop Fit Guide
- Bra Cup Volume Estimator
- Wireless Bra Fit Test Tool
Frequently Asked Questions (FAQ)
Is the Reddit Bra Calculator always correct?
No, it’s a highly accurate *starting point*. Breasts are three-dimensional, and factors like breast shape, root width, and projection can mean you need to go up or down a cup size, or try a sister size. Always check the fit!
What is a “Sister Size?”
A sister size shares the same cup volume but has a different band size. For example, a 34C has the same cup volume as a 32D and a 36B. If your band is too tight, you can try the next band up and the cup down (e.g., from 32FF to 34F).
Why do I need three bust measurements?
Using standing, leaning, and lying measurements captures different aspects of your breast tissue. This helps the calculator better estimate the volume, especially for projected, soft, or dense tissue, leading to a much more reliable cup size.
My band size is an odd number (e.g., 31). What should I do?
Most bra bands are made in even sizes (30, 32, 34, etc.). If your snug underbust is 31, the calculator will likely recommend a 32 band. You may consider using a bra extender on a new 30 band or using the tighter hook on a 32 band.