Bra Size Conversion Chart - Band & Cup Comparison

Underbust (cm)

Bust (cm)

Filter by region

Underbust ranges are measured in centimeters. Taiwan often lists both the centimeter value (e.g. 70) and the related US/UK number (e.g. 32).

Underbust range	US band
58 - 62 cm	28
63 - 67 cm	30
68 - 72 cm	32
73 - 77 cm	34
78 - 82 cm	36
83 - 87 cm	38
88 - 92 cm	40
93 - 97 cm	42
98 - 102 cm	44
103 - 107 cm	46
108 - 112 cm	48
113 - 117 cm	50
118 - 122 cm	52

How to measure bust and underbust

Keep a relaxed posture and measure on bare skin or with a thin, non-padded bra to reduce error.

Stand naturally, relax shoulders, avoid holding your breath.
Keep the tape level and snug to the body when circling underbust and bust points.
Thin wireless or unpadded bras are fine; thick padding can distort numbers.

Cup difference basics

A cup generally changes every 2–2.5 cm (about 1 inch) of bust-underbust difference; values are approximate references.

Taiwan/Japan often use 2.5 cm grading; some US/UK brands use 1-inch steps and name DD/DDD separately after D.
Actual fullness and shape still depend on design; use the table as a quick guide then confirm by trying on.

Fit reminders & disclaimer

Sizing varies by brand, country, fabric, and cup style; labels may mix centimeters and US/UK numbers.
The chart is for general reference only; the best size is the one that fits comfortably when tried on.

Sister size examples

Sister sizes share a similar cup volume with a different band. Adjust band down, go up one cup letter; adjust band up, go down one cup letter.

75C ≈ 70D or 80B80D ≈ 75E or 85C70B ≈ 65C or 75A

Check band tension and strap adjustability when moving between sister sizes; comfort comes first.

Underbust (cm)

Bust (cm)

Filter by region

Underbust ranges are measured in centimeters. Taiwan often lists both the centimeter value (e.g. 70) and the related US/UK number (e.g. 32).

Underbust range	US band
58 - 62 cm	28
63 - 67 cm	30
68 - 72 cm	32
73 - 77 cm	34
78 - 82 cm	36
83 - 87 cm	38
88 - 92 cm	40
93 - 97 cm	42
98 - 102 cm	44
103 - 107 cm	46
108 - 112 cm	48
113 - 117 cm	50
118 - 122 cm	52

How to measure bust and underbust

Keep a relaxed posture and measure on bare skin or with a thin, non-padded bra to reduce error.

Stand naturally, relax shoulders, avoid holding your breath.
Keep the tape level and snug to the body when circling underbust and bust points.
Thin wireless or unpadded bras are fine; thick padding can distort numbers.

Cup difference basics

A cup generally changes every 2–2.5 cm (about 1 inch) of bust-underbust difference; values are approximate references.

Taiwan/Japan often use 2.5 cm grading; some US/UK brands use 1-inch steps and name DD/DDD separately after D.
Actual fullness and shape still depend on design; use the table as a quick guide then confirm by trying on.

Fit reminders & disclaimer

Sizing varies by brand, country, fabric, and cup style; labels may mix centimeters and US/UK numbers.
The chart is for general reference only; the best size is the one that fits comfortably when tried on.

Sister size examples

Sister sizes share a similar cup volume with a different band. Adjust band down, go up one cup letter; adjust band up, go down one cup letter.

75C ≈ 70D or 80B80D ≈ 75E or 85C70B ≈ 65C or 75A

Check band tension and strap adjustability when moving between sister sizes; comfort comes first.

FAQ

Common questions and answers about this topic.

Why can the same cup letter look so different?

The letter only reflects bust-underbust difference. Band length, cup depth, padding, and style change the visual volume.

Why do same labeled sizes feel different across brands?

Brand patterns, cup shapes, fabric stretch, and wire length all affect fit. Some brands run tighter or looser by design.

What is a sister size?

It is an alternate size with similar cup volume but a different band, such as 75C close to 70D or 80B.

How to choose if two sizes both seem wearable?

Pick the one that stays firm without pressure: the band should sit level without digging, and straps adjust without slipping. You can also start with the loosest hook for longer wear life.

What is Bra Size Conversion Table?

Compare bra band sizes and cup measurements across Taiwan, US/UK, Europe, and Japan with optional filters.

Is Bra Size Conversion Table free to use?

Yes, Bra Size Conversion Table is completely free to use.