Chinese bra sizes usually use a centimeter band plus a cup letter. Convert the band first, then keep the cup label as a practical estimate.
Quick answer: 70A is about US 32A, 75B is about US 34B, 80C is about US 36C and 85D is about US 38D.
A 75B Chinese bra is usually close to US 34B.
A 80C Chinese bra is usually close to US 36C.
Cup shape and brand grading can vary.
Measure under-bust and bust in centimeters before buying.
This page answers one specific size search intent. For the best fit, start with the linked main converter and use the centimeter measurements on the Chinese chart whenever they are available.
Marketplace labels are useful shortcuts, but brand charts, garment type, fabric stretch and body measurements can change the final fit. Treat the lookup as a nearest match, not a guaranteed size.
Chinese size labels are practical lookup shortcuts, not universal brand guarantees. A CN shoe label, clothing size, bra code or Taobao chart row can vary by seller, product category, last shape, fabric stretch and whether the chart shows body measurements or garment measurements.
When possible, use the centimeter value first: foot length for shoes, bust/waist/hip for clothing, under-bust and cup difference for bras, and the specific Taobao chart row for marketplace listings. Then use the converter result as the nearest US, UK or EU match.
For the broader explanation, read Chinese bra size chart to US complete guide. For why these pages give estimates instead of promises, read Why Chinese size conversion is an estimate.