Smith Optics Bike Helmet Size Chart

1. Achieve the perfect fit by measuring your head circumference correctly.

2. Watch the video below to see how to measure your head correctly.

3. VIDEO: How To Measure For A Bike Helmet

Follow Heads Don’t Bounce on Youtube!

4. On the chart below, find the helmet model that you are interested in, then find your head measurement to see which size you need.

Smith Optics Bike Helmet Size Charts

ModelXS / Youth SSmallMediumLargeExtra Large
Convoy MIPS
51 – 55cm55 – 59cm59 – 62cm61 – 65cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”24⅞” – 26⅜”
Engage MIPS
51 – 55cm55 – 59cm59 – 62cm61 – 65cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”24⅞” – 26⅜”
Express &
Express MIPS
51 – 55cm55 – 59cm59 – 62cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”
Forefront 2 MIPS
51 – 55cm55 – 59cm59 – 62cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”
Ignite MIPS
51 – 55cm55 – 59cm59 – 62cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”
Jetstream TT MIPS
51 – 55cm55 – 59cm59 – 62cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”
Mainline MIPS
51 – 55cm55 – 59cm59 – 62cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”
Maze
51 – 55cm55 – 59cm59 – 62cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”
Network MIPS
51 – 55cm55 – 59cm59 – 62cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”
Persist MIPS
51 – 55cm55 – 59cm59 – 62cm61 – 65cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”24⅞” – 26⅜”
Podium TT MIPS

55 – 59cm59 – 62cm


21¾” – 23¼”23¼” – 24½”
Portal MIPS
51 – 55cm55 – 59cm59 – 62cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”
Route MIPS
51 – 55cm55 – 59cm59 – 62cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”
Rover MIPS
51 – 55cm55 – 59cm59 – 62cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”
Session MIPS
51 – 55cm55 – 59cm59 – 62cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”
Signal MIPS
51 – 55cm55 – 59cm59 – 62cm61 – 65cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”24⅞” – 26⅜”
Trace MIPS
51 – 55cm55 – 59cm59 – 62cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”
Venture MIPS
51 – 55cm55 – 59cm59 – 62cm

20⅛” – 21⅝”21¾” – 23¼”23¼” – 24½”
Wilder Jr. MIPS48 – 52cm



18⅞” – 20½”



Zip Jr. MIPS48 – 52cm



18⅞” – 20½”