The Short Answer
A T-shirt bra has smooth, seamless, molded cups designed to be invisible under fitted tops. A full cup has maximum-coverage multi-panel seamed cups designed for support and lift, especially in larger sizes. The T-shirt bra prioritizes invisibility; the full cup prioritizes engineering.
Construction Side by Side
| Feature | T-Shirt Bra | Full Cup |
|---|---|---|
| Cup construction | Single molded piece (seamless) | Multi-panel seamed |
| Cup surface | Smooth — no visible seams | Seams visible across cup face |
| Coverage | Moderate to full | Full — highest coverage |
| Padding | Light foam (for smoothing) | Usually none |
| Fabric | Microfiber, plain nylon | Varies — lace, embroidery, mesh |
| Size range focus | A–DD (most common) | D–K (built for larger sizes) |
| Under clothing | Invisible | Seams may show under thin fabric |
How to Tell Them Apart
Run your finger across the cup. If it's perfectly smooth with no seam ridges — T-shirt bra. If you feel seam lines crossing the cup — full cup. The seams in a full cup aren't a flaw; they're structural — each panel is cut to shape and support a specific area of the breast.
The Size Gap
T-shirt bras are the best sellers in A–DD, but they struggle above DD because a single molded piece can't provide the same lift as multi-panel engineering. Full cup bras are the workhorse of D+ lingerie — brands like Elomi, Panache, and Fantasie build their ranges around this silhouette because the seamed panels can handle the weight.
When to Wear Each
T-shirt bra: Under any fitted top where you need a clean line. The everyday go-to for A–DD.
Full cup: When support matters more than invisibility. Under thicker fabrics, blazers, and structured tops where seam show-through isn't a concern. The right choice for larger cup sizes where molded cups don't provide enough lift.