Bra Size Calculator
Estimate a practical US starting size from two measurements, then confirm it with a real fit check.
Use the same unit for underbust and full-bust measurements.
Place the tape directly beneath the bust where the bra band sits. Keep it level and comfortably snug.
Measure around the fullest part while wearing a light, unpadded bra or fitted layer. Keep the tape level.
Use the recommendation as a styling direction. Fabric, fit, comfort, culture, occasion and personal taste can change the best choice.
Use the interactive guide below as a private starting point. No measurement is stored or submitted by this calculator.
Measure under the bust snugly and the full bust at the fullest point. Use the same unit and avoid padding or bulky clothing during measurement.
Finding a comfortable bra starting point
A calculator narrows the shopping search; it cannot replace a real fit check. Band tension, cup volume, breast shape, style construction and stretch can all change how the same nominal size feels.
Explore next: Body Shape Calculator · Neckline MatcherMeasure the underbust
Place the tape directly beneath the bust where the band will sit. Keep it horizontal and comfortably snug. Do not pull the tape so hard that it digs into the body.
Measure the full bust
Measure around the fullest part while wearing a light, unpadded bra or a thin fitted layer. Keep the tape level and stand normally.
Check three fit zones
The band should sit level and feel secure. The cups should contain the bust without cutting in or leaving obvious gaps. Straps should support without carrying all the tension.
Use sister sizes when the fit is close
If cup volume seems right but the band is not, test a sister size as a next shopping experiment. Brand grading is different, so confirm with the brand’s own chart.
Fit note: comfort, returnability and the specific bra design matter more than protecting one calculator label.
Frequently Asked Questions
Is this a guaranteed bra size?
No. It is a US starting point. Brand grading, bra style, breast shape and fit preference can change the best size.
What is a sister size?
A sister size keeps a similar cup volume while changing the band. It can be useful when the cup feels close but the band needs adjustment.
How should the band fit?
A new bra should feel secure and sit level on the loosest hook without digging. The cups and straps should also work together.