A tank top is the most honest garment in the wardrobe. One thin layer of ribbed or jersey cotton, straps a finger wide, and armholes that start on the slope of the shoulder. Nothing about it hides anything, which is why it makes people reach for a bra that then shows at three places. The three problems are separate, and it helps to solve them separately.
What shows under a tank top?
The strap first. A bra strap is wider than a tank strap, so it shows at the edge on both sides, and no colour hides a strap edge against skin. The band second: a wide armhole shows the side of the band under the arm, especially when you lift an arm. And the fabric itself: ribbed cotton is thin and stretchy, and it prints whatever is under it, including a nipple, a lace edge or the seam of a cup.
| The problem | Why it happens | The fix |
|---|---|---|
| Strap shows at the edge | Tank straps are narrower than any bra strap | Match a strap on purpose, or go strapless or adhesive |
| Band shows under the arm | The armhole is cut wide | A cup with no band |
| Fabric prints | One thin stretchy layer | Covers, with or without anything else |
Do you need a bra under a tank top at all?
Often not, and for a lot of tank tops the honest answer is covers only. A cotton tank with a built-in shelf, or a fitted rib that holds its own shape, needs coverage more than support, and reusable nipple covers give that with no strap, no band and no edge anywhere near the armhole. Can nipple covers replace a bra sets out when that is enough and when it is not.
When it is not, the question becomes the same one as a sleeveless dress, because the armhole is the same problem: a bra for a sleeveless dress sorts the options by how far in the armhole is cut. The tank version of that ladder is below.
Which strap route?
Three honest ones. Match a strap and let it show, which works with a plain strap in the tank's colour and is the option people forget; a bra for a spaghetti strap dress makes the case for it. Go strapless, where the strapless adhesive bra gives a band's support with a clasp at the centre, sized 30A to 40D, under a tank whose armhole is not so wide that the band's side would show. Or go band-free with the butterfly stick-on bra, which anchors high on the chest and leaves both the strap line and the underarm clear, in cup sizes A-B, C and D-D++.
Under a ribbed tank, the third route has an extra point in its favour: it has no edge to print. A moulded cup's outer edge can show through rib as a faint line, where the butterfly's fabric edge and a cover's thin silicone edge do not.
What about a white tank?
Skin-tone covers, not white ones. White under white shows as a brighter patch; your own shade under white disappears. The bio-glue covers and the reusable ones both come in more than one skin shade for this. The rule is the same one what to wear under a white shirt sets out, and it applies to any pale tank.
The gym tank
A gym tank is worn over a sports bra, and the tank is not the problem; the bra is. A thin or light-coloured sports bra prints through a fitted tank in exactly the way a cotton tank does, and covers under the sports bra solve it. Nipple covers for the gym covers which ones hold through sweat and which shade to pick under a pale bra.
The layered tank
A tank under an open shirt or a blazer is coverage work only, since the outer layer does the rest. Covers under the tank, and nothing else, is the usual answer; the strap question only returns if the shirt comes off.
The short version
Split the three problems. Strap: match it on purpose, go strapless, or go band-free. Band: a wide armhole wants a cup with no side, which is the butterfly. Fabric: covers, in your skin tone under a pale tank, which are also the whole answer under a tank that holds its own shape. At the gym, put the covers under the sports bra rather than fighting the tank. What to wear under any neckline will take the tank's cut and your cup size and pick one.
