Put your hand flat on a table. Measure your hand across the knuckles, thumb excluded, for normal glove size. Those at the lower end of the size, who want a closer fit, order one size smaller. Another way to measure is to take the circumference of your hand. Both of these measurements will give you an idea of your range. Those at the upper end of the size, who want a looser fit, order one size larger.
Grenade brand gloves run small, so order a size larger than the size recommended on the chart.