Bra Size Sanity Checker

First, it checks that your measurements make sense together: loose underbust should be ≥ snug underbust, and your standing bust should be larger than your underbust. Next, it estimates your likely cup difference from bust minus snug underbust, and uses the gap between loose and snug underbust (“measurement spread”) as a reliability signal. Finally, it compares the size implied by your measurements to the calculator-reported size, then nudges the recommendation using your fit feedback (band vs cup symptoms).

If your snug and loose underbust are close together, your tension/stance likely stayed consistent—so the implied bra size is more trustworthy. A large spread usually means measurement technique varied (different posture, arm position, breathing, or tape tension), so even a precise-looking calculator result may be unreliable. Also, this tool can’t fully account for breast shape, firmness, projection, or brand/style fit differences—so “likely inaccurate” often indicates you should re-measure or consider shape mismatch rather than abandoning your size entirely.

Use the same unit system for all inputs (inches vs cm). If standing bust isn’t greater than underbust, the calculator logic can’t produce a meaningful cup estimate—treat it as a likely measurement error. If your measurements vary widely, prioritize re-measuring with the same posture and tape tension before trusting any single calculator; then use the recommended sister-size steps only as a quick verification path.