Maternity Size Calculator: What Maternity Size to Buy in Each Trimester
Free tool · Updated October 2, 2026 · By CouponTalk
Your result
Enter your measurements to see your result.
Quick answer
Maternity clothes are sized by your pre-pregnancy size: if you wore M before, buy maternity M. The extra room for your bump is built into the panels and stretch fabric. In the first trimester a belly band and your own clothes are usually enough. Size up one only if you were at the top of your size before, or you are carrying twins.
How to measure
- Pick the size you wore before pregnancy.
- Choose your trimester.
- Tell us whether you were at the top of your size, or expecting twins.
Maternity Size Chart
| Trimester | What usually fits | Buy now |
|---|---|---|
| First (1–13 weeks) | Your own clothes | Belly band, soft wire-free bra |
| Second (14–27 weeks) | Maternity, same size as before | Bottoms with a bump panel, a re-fitted bra |
| Third (28–40 weeks) | Same maternity size | Nursing bras at about 35–37 weeks |
Every pregnancy is different. Choose comfort first, and ask your doctor about any discomfort.
Frequently asked questions
When should I start wearing maternity clothes?
Most women switch in the second trimester, around weeks 14–20, when regular waistbands get tight.
Will maternity clothes fit after delivery?
Many do for the first few weeks, which makes them useful postpartum too.
When should I buy a nursing bra?
Around weeks 35–37, when your size is closer to what it will be while feeding. Choose one that fits on the tightest hook.
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