UGGs with zippers, heels, or rubber-heavy constructions (like the Adirondack) often have less "give" and run true to size.

For the (the iconic tall, short, and mini boots), the consensus is often to size down .

The question of whether to size up or down in UGG boots is a classic debate for any fan of the brand. Because UGG uses high-quality sheepskin and a unique construction style, the way they fit on day one is rarely how they feel on day thirty. To get the perfect fit, you generally need to lean toward a snugger start. The Material Factor

Most Classic UGGs do not come in half sizes. If you typically wear a 7.5, dropping down to a 7 is usually the safest bet.