300cc vs 400cc Breast Implants: Which Should I Choose?

November 10, 2026

300cc or 400cc? Neither one is the "right" answer. They're two different looks, and both are among the sizes surgeons use most. 400cc holds 100cc more per implant, about a third more volume. That's a little less than half a measuring cup on each side. In clothes, the difference is usually easy to see. The real question is which look you want to live with every day.

Many women end up torn between these two numbers: 300cc feels safe, and 400cc feels like a real change. This guide helps you work out which side you're on, with a simple five-day test you can do at home, in your own clothes, before your consultation.

Are 300cc and 400cc both common sizes?

Yes. In the American Society of Plastic Surgeons' 2025 survey of its member surgeons, 89% named 300–400cc among their most-used implant volumes.¹ So if you're choosing between 300cc and 400cc, you're choosing within the most common range. Neither end is unusual.

The same survey found more surgeons seeing patients trend toward smaller implants (36%) than larger (12%), while about half saw no change.¹ That's useful context, but it describes what women are asking for, not what suits you. A trend can't tell you whether 300cc or 400cc will look right in your own wardrobe.

	300cc	400cc
Volume per implant	300cc	400cc (100cc, about one-third, more)
The look many women describe wanting	"My clothes fit better." A fuller shape that reads as natural.	"I can see a change." A fuller look that's noticeable in fitted clothes.
Cup size	Can't be predicted from cc alone. It depends on your band size, starting volume and the bra brand.
Best way to compare	Wear each one for full days in the same clothes, then see which one you miss.

How different do 300cc and 400cc look?

Here's the same model with no sizers and then wearing each size, so you can compare 300cc and 400cc separately against the same starting point. Slide each image to see the change.

Compare the same model without sizers and wearing 300cc, then 400cc, external sizers in the pocket bra. Look at how the top of the fabric sits in each.

Model wearing 300cc Oumènta breast implant sizers in a pocket bra — No sizers vs. 300cc

Same model wearing the pocket bra without breast implant sizers — No sizers vs. 300cc

Model wearing 400cc Oumènta breast implant sizers in a pocket bra — No sizers vs. 400cc

No sizers versus 300cc and 400cc external sizers on one model. External sizing demonstration only. Not a prediction of surgical results.

Keep in mind that this is one woman. Your frame changes how each size reads. On a narrower frame, 400cc can look fuller than you expect, which our "Is it too big for my body?" guide covers. On a wider frame, 300cc can look more modest than you expect, as our larger-frame guide explains.

Photos also flatten the difference. A side-by-side picture shows you volume. Your clothes show you how a size changes the way you dress, and that's what you'll notice every morning.

Which side are you on: 300cc or 400cc?

Before you try anything on, it helps to know what you're hoping for. These aren't rules, just a way to notice which way you're already leaning.

You may lean toward 300cc if…	You may lean toward 400cc if…
You want your clothes to fit better more than you want people to notice a change.	You want a change you can see in a fitted top from across the room.
You're very active and want a size that stays out of the way.	You've felt "flat" in clothes for years and want them to look filled out.
"Natural" is the most important word in your goal.	"Proportionate to my hips" or "balanced" is the most important word.
You'd rather keep wearing the clothes you own now.	You're happy to rethink some of your wardrobe.

If your answers land on both sides, that's normal. It usually means you need to see both sizes for real, not decide on paper. If "natural" is your main goal, our guide to choosing a natural-looking size helps you turn it into something specific.

Should you lean toward 400cc if you're unsure?

Research showing that about 1 in 4 women surveyed would have preferred a different breast implant size.

Not automatically, but give it a fair trial. In one study, 1 in 4 women would have preferred larger breasts after augmentation, and fewer than 1 in 50 would have preferred smaller.² Most of those women were still happy with their surgery. You can be happy with your breast augmentation and still wish you'd chosen a different size.

For someone torn between 300cc and 400cc, that pattern is worth knowing. A first instinct often leans cautious, and 400cc can feel like "a lot" in the first hour and ordinary by the end of the day. Our guide to whether to go bigger covers this in more detail. The answer still isn't "pick the bigger one." It's to wear both long enough to know. Sizers can't predict your result or how you'll feel after surgery.

How do I choose between 300cc and 400cc? The "which one did you miss?" test

Two days in each size is the heart of this test. One day isn't always enough for a new size to stop feeling new. Then you go back to the first size, and your reaction tells you a lot.

Days	Wear	What to notice
1–2	300cc	Work, errands, dinner. Does your favorite fitted top look the way you hoped?
3–4	400cc	Same outfits. Does it still feel like "too much" on day 4, or has it started to feel like you?
5	Back to 300cc	The deciding day. Do you feel relieved, or do you miss 400cc?
Only if needed	350cc	If you missed neither size strongly, try the middle. Don't start here.

Wear the same outfits on matching days: a fitted tee, a button-down, a dress you love and whatever you wear most on weekends. Take photos in the same spot and light. Our photo guide shows how to keep them fair.

Why not start with 350cc? Because the middle can feel like the careful choice without telling you anything. Our 425cc guide explains this "split-the-difference trap." And if you miss 400cc strongly on day 5, test one more step up before your consultation. An Oumènta custom sizer kit lets you choose three pairs, so 300cc, 350cc and 400cc fit in one kit.

Everything comes in one kit, ready to wear, and it's yours to keep.

Your Oumènta kit includes the pocket bra, in your size, with your sizers. There's no need to find a sports bra that will hold them. The built-in pockets keep each sizer where it belongs, and the adjustable straps let you get the fit right. Then wear each size in your own clothes, to work, on errands and out to dinner, and see it the way you'll actually live with it. There's no rental clock and nothing to send back, so you can take your time and try sizes again before your consultation. Sizes run from 200cc to 500cc in 25cc steps, so you can compare sizes that are close together, too.

What to bring to your consultation

Your surgeon will look at things a sizer can't, such as your chest width, your tissue and which implant profile fits your body. Our guide to implant profile, width and projection explains why the same cc can look different. What you can bring is a clear answer about the look you want.

Which size you missed on day 5, and how strongly
Your matching photos in the same outfits
The one outfit that made the decision obvious
A simple sentence, such as "I liked 400cc in my clothes, but I want it to look natural from the side"

For the full decision process, see how to choose the right breast implant size.

See Oumènta in Everyday Life

From workouts to everyday outings, see how Oumènta breast implant sizers look beneath clothing.

Woman wearing Oumènta sizers beneath a shirt while exercising on a lat pulldown machine — At the gym

Woman wearing Oumènta sizers beneath workout clothing while lifting dumbbells — Everyday movement

Woman wearing Oumènta sizers beneath casual clothing while walking outdoors — Out and about

Woman wearing Oumènta sizers beneath a shirt while using gym equipment — Working out

Woman looking at her silhouette in a mirror while wearing Oumènta sizers beneath clothing — See your silhouette

Woman wearing Oumènta sizers beneath everyday clothing while walking outdoors — Everyday wear

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Frequently asked questions

Is there a big difference between 300cc and 400cc breast implants?

400cc holds 100cc more per implant, about a third more volume. In fitted clothes the difference is usually easy to see, but how big it looks depends on your frame and starting size.

How many cup sizes is 300cc vs 400cc?

There's no reliable conversion. Cup size depends on your band size, your starting volume and the bra brand. Trying each size in your own clothes tells you more than a cup estimate.

Is 400cc too big?

Not necessarily. It's within the most common range: in ASPS's 2025 survey, 89% of surgeons named 300–400cc among their most-used volumes. Whether it's too big for you depends on your frame and the look you want. Wear it for two full days before deciding.

Should I just choose 350cc if I'm torn?

Try 300cc and 400cc first. If you clearly prefer one, you have your answer. Only try 350cc if neither one felt right, so the middle is a real choice, not a compromise.

Can sizers show me what 300cc or 400cc implants will look like?

They show you how each volume looks in your clothes. They can't predict your surgical result, which depends on your anatomy, the implant profile and your surgeon's technique.

Sources

American Society of Plastic Surgeons. Breast surgery in 2025: Evolving aesthetics. 2026. ASPS member surgeon survey: 36% saw patients trending toward smaller implants, 12% larger, 52% no change; 300–400cc named among most-used volumes by 89% of surgeons. https://www.plasticsurgery.org/news/articles/breast-surgery-in-2025-evolving-aesthetics
Swanson E. Prospective Study of Saline versus Silicone Gel Implants for Subpectoral Breast Augmentation. Plastic and Reconstructive Surgery Global Open, 2020. 171 survey respondents: 25.1% would have preferred larger, 1.8% smaller; 98.8% would have the surgery again. https://pmc.ncbi.nlm.nih.gov/articles/PMC7339341/

This article is general information about trying sizes in clothing. It isn't medical advice. Oumènta sizers are apparel products, not medical devices, and can't predict surgical results. Talk with a qualified, board-certified plastic surgeon about implant selection.

Oumènta Editorial Team • Not medically reviewed

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