A jacket can be the main event, but its base layer changes the whole outfit. A plain or restrained regular-fit tee is often the easiest place to start.
Start at the neckline
A crew neck gives an open jacket a clean frame. Check how high it sits and whether you like the amount of tee visible. A tank creates a more open line, while a higher neckline makes the layers feel closer together.
Try the combination with the jacket both open and closed. The base layer should feel comfortable around your neck and shoulders in either position.
Leave room inside the jacket
A regular or closer fit is usually easier to layer beneath a fitted jacket than a very wide tee. Under a roomier overshirt, you have more freedom. Pay attention to fabric gathering around the upper arm and underarm.
Move your arms, sit down and reach forward. If the layers bunch or pull, try less sleeve volume or a different jacket size. The right combination should work beyond a mirror photograph.
Decide how much hem to show
A tee finishing near the jacket hem keeps the outline simple. A longer tee can add another visible layer, but the difference should feel deliberate. Check the side view and try a tuck before deciding the piece is wrong.
Colour can do some of the work too. A quiet neutral lets the outer layer stand out; a contrasting tee makes the opening of the jacket more noticeable.
Match the fabric to the day
Fabric weight, texture and your local weather matter more than a label such as essential. A lighter base can feel easier under a substantial jacket; a heavier tee can hold its shape when you take that jacket off.
Browse Polos & Regular for everyday base layers and Outerwear for jackets and overshirts. Compare fabric details and measurements at the store, then use Pair up with to explore alternatives around the piece you like.