OS1st Size Chart

Please use your shoe size to find the perfect OS1st fit for you!
Sock Size Men Women Euro Ankle Circumference
Small 3-5.5 4-6.5 33-36 5-8"
Medium 6-9.5 7-10.5 37-41 7-10"
Large 10-13 11+ 42-46 9-13"
X-Large 13.5-15 47-50 11-15"
XX-Large 15.5+ 51+ 13-18"
OS1st Calf Sleeve Sizing
Sock Size Men Women Euro Ankle Circumference Calf Circumference
Small 3-5.5 4-6.5 33-36 6.5-8.5" 9.5-14.5"
Medium 6-9.5 7-10.5 37-41 8.5-10.5" 12-17"
Large 10-13 11+ 42-46 9.5-12.5" 14-19"
X-Large 13.5-15 47-50 12-14" 14.5-20"

For sizing assistance, call our toll-free customer service line at 1-866-446-2767.