correct bra size calculator

How to use this correct bra size calculator

This tool gives you a practical starting point for finding your bra size. It uses a simple, modern fit approach: estimate your band size from your underbust measurement and estimate your cup size from the difference between your bust and band.

• Measure your underbust snugly, directly under your breasts.
• Measure your full bust at the fullest point, keeping the tape level.
• Enter both values above and click Calculate Size.
• Use the result as a baseline, then fine-tune by brand and style.

Understanding bra sizing: band + cup

Band size

The band provides most of a bra’s support. In US sizing, band sizes are usually even numbers (30, 32, 34, 36, etc.). A well-fitted band should feel secure on the loosest hook when new, without riding up your back.

Cup size

Cup size is based on the difference between your bust measurement and your band size. Roughly: 1 inch is A, 2 inches is B, 3 inches is C, 4 inches is D, and so on. This calculator rounds to the nearest inch for a clear recommendation.

Sister sizes

Sister sizes have the same cup volume with a different band length. For example, 34C, 32D, and 36B are sister sizes. If your cup feels right but your band feels too tight or too loose, sister sizing helps you adjust intelligently.

How to measure correctly at home

1) Underbust measurement tips

• Use a soft measuring tape and keep it parallel to the floor.
• Measure while standing upright and breathing normally.
• Keep the tape snug, not painfully tight.
• Take two measurements and average if needed.

2) Full bust measurement tips

• Measure around the fullest part of your chest.
• Wear a non-padded bra (or no bra if that is more consistent for you).
• Do not compress tissue with the tape.
• Make sure the tape stays level front and back.

Signs you may be wearing the wrong bra size

• Band rides up in back (often means band is too loose).
• Straps dig in deeply (band may not be providing enough support).
• Spillage over cup edges (cup likely too small).
• Gaps in cups (cup shape or size may be off).
• Center gore does not sit flat (fit mismatch in cup or band).

Important fit notes

A calculator can’t account for every body shape or every bra design. Different brands vary in stretch, cup depth, wire width, and sizing consistency. Use your calculated size as a strong starting point, then test nearby sizes based on comfort and support.

If you’re between sizes:

• Choose the firmer band if you want more support.
• Choose the larger cup if you see cutting-in or spillage.
• Try sister sizes if only one part of the fit feels off.

FAQ

Is this bra size calculator accurate?

It is accurate as a starting estimate and works well for many people. Final fit should still be confirmed by trying on bras, because style and brand differences matter.

Does this tool use US or UK bra sizing?

The output is in US-style sizing notation (for example, DD and DDD/F). If you shop UK brands, convert the cup progression accordingly.

Can body changes affect bra size?

Yes. Weight changes, hormonal cycles, pregnancy/postpartum, and training changes can all affect fit. Re-measuring every few months is a good habit.

Should I trust comfort over the label?

Absolutely. The best bra size is the one that gives you comfort, support, and a stable fit throughout the day.

Bottom line

A correct bra size can improve posture, comfort, and confidence. Use this calculator to quickly estimate your band and cup, then fine-tune with real-world try-ons and sister sizes. The goal isn’t just a number—it’s a better fit.