A beach towel is and should be larger than your regular bath towel. It should be big enough for you to dry yourself after swimming and lie down fully on the beach. Typically, it measures 30” x 60”. Some good 30” x 60” towels include the following:
Amazon Basics Cabana Stripe Beach Towel
Ben Kaufman 6-Pack Yarn Dye Stripes Oversized Towel
Utopia Towels Cabana Stripe Beach & Pool Towels
However, many models come in bigger sizes than average. The following options, for example, are available in a 78” x 35” variety:
Elite Trend Beach Towel
Dock & Bay Quick Dry Beach Towel