38B to 38D Breast Implants: How Many CCs on a Larger Frame?

Going from a 38B to a 38D usually means testing somewhere around 300cc to 450cc per side. One lab study found that wider bands need about 150cc for each cup size, so two cups on a 38 band start at roughly 300cc. On a broader frame, 300cc can look smaller than expected. That's why the range runs higher than the "A to C" numbers you may have seen online.

There's a second thing most size charts skip: a 38B isn't a small starting point. By standard bra sizing, a 38B uses the same cup as a 34D. So this article isn't about whether you're "too small to go big." It's about choosing a volume that looks in proportion on a wider frame, without stopping short.

Your 38B Is Already a 34D

Bra cups are built in step with the band. Researchers who studied bra sizing put it plainly: the cup pattern used for a 34D is the same as a 36C and a 38B (Dal Cin & Jeans, 2005). The same rule runs one step further for your goal. A 38D shares its cup with a 36DD and a 40C.

Sister sizes follow the rule "one band up, one cup down." Brands differ, so treat this as a guide, not a measurement. For more on how sister sizes work, see 34A to 34C breast implants.

Why this matters: when a friend on a 34 band says she went "two cups up with 300cc," her starting point and yours aren't the same. Your goal, a 38D, holds the same amount as a 36DD. If you've read our 36B to 36DD guide, you're aiming at a similar finish line, starting from a bigger base.

How Many CCs Is One Cup on a 38 Band?

The old rule of thumb was 100cc per cup. A 2017 study that filled bras with measured volumes found that number was too low. It recommended telling patients that one cup size takes about 130cc to 150cc, with narrower bands near 130cc and wider bands near 150cc (King et al., 2017). A 38 band sits at the wide end of that range.

This is also why the per-cup numbers on our other cup-to-cc pages vary. A narrower band like a 32 uses less volume per cup, and a 38 uses more. The general A cup to D cup guide uses the middle of the range. On a 38 band, plan from the high end.

The Bigger Risk on a Larger Frame: Stopping Short

Women on a smaller band often worry about going too big. On a 38 band, the more common worry runs the other way: "Will anyone even notice?" A volume that looks dramatic on a narrow chest spreads across a wider one. 300cc on a 38 band can read as a modest change in clothes.

Research backs up how often size preference lands on the "bigger" side. In one study of 341 women surveyed three months after augmentation, about 1 in 4 said they would have preferred a different size: 16.7% wished they were larger and 7.3% wished they were smaller (Brown et al., 2021). Most women were still content with their result. You can be happy with your breast augmentation and still wish you'd chosen a different size.

Trying sizes at home can't predict your surgical result or guarantee you'll be happy with it. What it can do is show you how each volume looks in your own clothes, on your own frame, so the number you bring to your surgeon is one you've actually seen.

What 400cc Looks Like in a Pocket Bra

The model below has a narrower frame than a 38 band. Keep that in mind: the same 400cc will look less projected on a wider chest. Use the slider to see how much shape the sizers add in the bra, then picture that volume spread across your own width.

Compare the same model without sizers and wearing 400cc external sizers in the pocket bra. Notice the added fullness at the top and front of the cup.

No sizers versus 400cc external sizers. The model's frame is narrower than a 38 band. External sizing demonstration only. Not a prediction of surgical results.

If 400cc looks like "a lot" on the model, that's normal. It's the reason to try volumes on your own body instead of judging from someone else's photo. For a closer look at volumes in this range, see 350cc vs. 450cc and 400cc vs. 500cc.

One fitting tip for a 38 band: pick the pocket bra that fits the body you have now, not the size you're hoping for. A bra that's tight around the band will squeeze the sizers flat and make every volume look smaller than it is.

The Larger-Frame Proportion Test

On a narrow frame, the question is "Is this too big for my body?" On a 38 band, ask a different question: "Does this look in proportion with my shoulders, ribcage and hips?" Start with three volumes, such as 350cc, 400cc and 450cc, and wear each one for at least a few hours. Then run these five checks:

1. The side view in a fitted top. Stand sideways to a mirror. Does your bust line come forward past your ribcage and tummy line, or does it blend in? On a wider frame, a volume that doesn't clear that line can look like "nothing changed."
2. The shoulder check. Look straight on in a fitted tee. Does the bust look balanced with your shoulder width, or do your shoulders still look wider than your chest?
3. The button-down test. Wear a shirt that fits your shoulders now. Note where it gaps. Some gapping might be a trade you're happy with, or it might tell you a size is past what you want.
4. The everyday outfit. Wear what you'd wear on a normal Tuesday. If you only like a volume in a swimsuit, keep testing.
5. The end-of-day check. After several hours, does the size still feel like you? A volume that excites you in the first ten minutes can feel different by evening.

If all three volumes pass the shoulder check and you still wish for more, try 450cc against 500cc. If 350cc already feels like plenty, step down and compare 300cc. Our 450cc everyday clothes guide has more outfit ideas for the upper end of the range.

These are starting points for at-home testing, not implant recommendations. Your surgeon will decide which implant dimensions suit your chest.

What to Bring to Your Consultation

A cup letter means different things to you, your surgeon and every bra brand. Volume is the language your surgeon works in. After testing, bring the volume you liked best, the one that felt too small and the one that felt like too much. Add a few side-view photos in the same fitted top (see how at-home sizing works).

Your surgeon will look at your chest width and tissue and may suggest a different volume or profile. That's expected. Profile changes how the same volume sits, which matters on a wider chest. Our profile guide explains width and projection, and the size-choosing framework walks through the whole decision.

Frequently Asked Questions

This article is for general education about trying breast implant sizes with external sizers worn in clothing. It isn't medical advice. Oumènta sizers are apparel products and can't predict surgical results. Talk with a board-certified plastic surgeon about your options.

Oumènta Editorial Team • Not medically reviewed