To understand Lululemon sizing, it's important to get familiar with their fabrics, as these dictate the level of compression and stretch within their bras and leggings . Whether you should size up or down in a Lululemon product depends on the fabric.
Everlux™ is a technical fabric that features a double-knit construction to keep you cool and dry during intense workouts. It's designed for sweaty studio sessions, so needs to be compressive (read: tighter) to be able to perform properly. We recommend you size up in Everlux™.
Luon® is breathable and soft, and designed with a 4-way stretch for a more comfortable fit. This material is better for yoga and light workout activities. It has a light compression for a body-hugging feel. We recommend you buy your true size in their Luon® fabric.
Luxstreme® is a high-performance fabric that fits like a second skin. Designed for HIIT and running, Luxstreme® has a more compressive fit to help support the muscles. Your true size is normally fine in Luxstreme®.
Nulux™ is a super-soft fabric that feels silky and contours to the body. It's very lightweight and only offers light compression. Because of its lightweight fabric, it might not be the most squat proof of styles. We recommend buying a smaller size in Nulux™, but if you're buying a lighter pair stick to your true size as a bigger size will make them less see-through.
Nulu™ has a second-skin fit and a buttery soft finish. It's not compressive but it's very lightweight, making it ideal for light exercises like yoga and casual wear. Either a size down or your true size is normally fine in Nulu™.
As a general rule, consider sizing up in more compressive styles, stick to your true size in styles with medium compression, and consider sizing down in styles with little compression.