Thinkstock Images/Comstock/Getty Images

Choosing a pair of new earrings becomes more complicated when you are considering selecting a new gauge size. Shop for new jewelry -- either for your ears or your body -- with confidence when you know the difference between common gauge sizes like 18 gauge and 16 gauge.

Gauge Sizing

Though it seemingly goes against logic, earrings and other jewelry gauge sizes actually get bigger the lower the number of the gauge. An 18 gauge, one of the smallest gauges, is actually smaller than a 16 gauge earring, with the largest gauges being 0, 00, and 000 gauge jewelry.

U.S. Gauge Conversion

The United States typically measures gauges in inches, unlike most other countries. In the U.S. an 18 gauge earring measures approximately 5/128-inch while a 16 gauge earring measures 3/64-inch, for a difference of 1/128-inch or approximately 0.0078 inches.

Metric Gauge Conversion

Gauge sizes are more often listed in millimeters for a simpler measurement standard. An 18 gauge earring measures approximately 1.0 mm and a 16 gauge earring measures approximately 1.2 mm, for a difference of 0.2 mm.

Choosing a Gauge Size

While the difference in size between an 18 and 16 gauge earring may seem negligible, you should always check with a professional piercer to choose the best size for your particular piercing for best results. Earrings and jewelry also come in different lengths, so choose an appropriate gauge and length for the most comfortable piercing. An 18 or 16 gauge is a popular choice for ear, nose, lip and eyebrow piercings, though 16 gauge is also often used for septum or genital piercings.