US sizes are different from European and Asian sizes, and they also differ by brand. Try clothes on, or read the size chart for each brand.
Men's clothes: shirts are S, M, L, XL, or by neck and sleeve length in inches. Pants are by waist and length, for example 32 x 30 means a 32-inch waist and 30-inch leg.
Women's clothes: numbers like 2, 4, 6, 8, 10, or S, M, L. A US size is usually smaller in number than the same size in Europe or the UK.
Children's clothes: by age or height, for example 4T (toddler, about 4 years) or 10-12.
Shoes: men's and women's sizes are on different scales. A woman's US size is usually about 1.5 higher than a man's US size for the same foot. Wide feet: look for "W" or "wide".
One inch is 2.54 centimeters. To convert, measure yourself in centimeters and divide by 2.54.
Reading a size chart online
Measure your chest, waist and hips with a soft tape, and your foot length from heel to longest toe.
Open the size chart link on the product page.
Compare in inches or centimeters, not your size at home.
Read reviews: people often say "runs small" or "runs large".
Check the return policy before you order.
Dressing for cold weather
Large parts of the US have winters well below freezing (0°C is 32°F). The wind chill (how cold it feels with wind) can make it much colder.
Dress in layers: a thin base layer, a warm middle layer (fleece or sweater), and a windproof, waterproof coat.
Cover your head, hands and ears. Frostbite (skin freezing) can happen fast on very cold, windy days.
Wear waterproof boots with grip for snow and ice.
Buy coats in October, before the first cold days, or at end-of-season sales in February.
Dressing for heat and indoor cold
Summers can be very hot and humid in the South and very dry in the Southwest. Wear light colors and a hat, and carry water.
Offices, buses, cinemas and classrooms are often air-conditioned and cold even in summer. Bring a light sweater.
Buying a winter coat at home that is not warm enough here. A warm coat bought here is often the better choice.
Shipping all your clothes. Thrift stores sell good winter clothes cheaply (see the thrift guide).
Wearing cotton in snow. Wet cotton makes you cold. Wool and synthetic fabrics stay warmer when wet.