Maternity Bra Size
Calculator UK
Your body goes through significant changes during pregnancy, and your bra size will adapt along with it. Choose your pre-pregnancy or current UK size below to see estimated adjustments for each trimester.
Maternity Bra Size Calculator
Sports Bra Size (UK)
Sports bras in the UK typically follow the same band/cup sizing. However, for high-impact sports, go down one cup size for extra support.
| Impact Level | Fit Advice | Cup Guide |
|---|---|---|
| Low | Yoga, Walking | Your usual cup size |
| Medium | Cycling, Hiking | Your usual cup size |
| High | Running, HIIT | Go down 1 cup for support |
Maternity Bra Tips
- ✓ Your size can increase by 2–4 cup sizes during pregnancy
- ✓ Buy maternity bras in your 3rd trimester for best fit
- ✓ Look for adjustable bands and extenders
- ✓ Re-measure after delivery and during breastfeeding
Maternity Bra FAQs
How do I calculate my maternity bra size?+
Start by entering your pre-pregnancy or current UK size in our calculator above. On average, expect to drop down a band size and go up one cup size by the end of the first trimester, with further changes as you reach the third trimester. If your ribcage expands, look for sister sizes with larger bands and smaller cups.
When should I buy a maternity bra?+
Around weeks 12 to 16, most expectant mothers feel their normal bras becoming too tight. It is wise to purchase only one or two transition bras, as your sizing will likely continue to shift throughout pregnancy and into nursing.
What is the difference between a maternity bra and a nursing bra?+
Maternity bras focus on comfortable support during pregnancy (using stretchier materials and wire-free shapes). Nursing bras include all those features but add drop-down clasps or crossover designs for convenient nursing access.
Can I wear an underwire bra during pregnancy?+
UK fitting experts and midwives generally suggest switching to wire-free options, especially after the first trimester. Underwires can compress developing tissue and block milk ducts. Stretchy, wire-free maternity styles offer flexible support and greater comfort.