Please take all measurements carefully, ideally using some help.

Measurements 1,2,3 and 4 are circumferences. 
While measuring do not hold measuring tape too tight or too loose. It should be neutral.

1) Forehead - measure just over your eyes

2) Mouth level - measure just under your mouth (between bottom lip and chin). Try to make the measuring tape lay naturally on the back of your neck in the shortest path. Please keep your mouth closed while measuring and head pointed straight forward.

3) Neck - measure in the middle of the neck.

4) Chin - measure from the tip of your chin to the back-top of your head.

5) Nose length - measure from the middle of the eyes level to the tip of your nose.

6) Nose base - measure from the point your nose connects with your face to the tip of your nose.

Sizes reference chart:

XS
S
M
L
XL
Forehead
52-53
54-55
56-57
58-59
60-61
Mouth level
38-40
41-44
45-48
49-51
52-54
Neck
28-31
32-34
35-38
39-42
43-46
*All sizes are in cm (1cm=0.3937inch)

1) Forehead - - - 50 cm50.5 cm51 cm51.5 cm52 cm52.5 cm53 cm53.5 cm54 cm54.5 cm55 cm55.5 cm56 cm56.5 cm57 cm57.5 cm58 cm58.5 cm59 cm59.5 cm60 cm60.5 cm61 cm61.5 cm62 cm62.5 cm63 cm63.5 cm64 cm64.5 cm65 cm

2) Mouth level - - - 36 cm36.5 cm37 cm37.5 cm38 cm38.5 cm39 cm39.5 cm40 cm40.5 cm41 cm41.5 cm42 cm42.5 cm43 cm43.5 cm44 cm44.5 cm45 cm45.5 cm46 cm46.5 cm47 cm47.5 cm48 cm48.5 cm49 cm49.5 cm50 cm50.5 cm51 cm51.5 cm52 cm52.5 cm53 cm53.5 cm54 cm54.5 cm55 cm55.5 cm56 cm56.5 cm57 cm57.5 cm58 cm58.5 cm59 cm59.5 cm60 cm60.5 cm61 cm61.5 cm62 cm62.5 cm63 cm63.5 cm64 cm64.5 cm65 cm

3) Neck - - - 26 cm26.5 cm27 cm27.5 cm28 cm28.5 cm29 cm29.5 cm30 cm30.5 cm31 cm31.5 cm32 cm32.5 cm33 cm33.5 cm34 cm34.5 cm35 cm35.5 cm36 cm36.5 cm37 cm37.5 cm38 cm38.5 cm39 cm39.5 cm40 cm40.5 cm41 cm41.5 cm42 cm42.5 cm43 cm43.5 cm44 cm44.5 cm45 cm45.5 cm46 cm46.5 cm47 cm47.5 cm48 cm48.5 cm49 cm49.5 cm50 cm50.5 cm51 cm51.5 cm52 cm52.5 cm53 cm53.5 cm54 cm54.5 cm55 cm55.5 cm56 cm56.5 cm57 cm57.5 cm58 cm58.5 cm59 cm59.5 cm60 cm60.5 cm61 cm61.5 cm62 cm62.5 cm63 cm63.5 cm64 cm64.5 cm65 cm

4) Chin - - - 58 cm58.5 cm59 cm59.5 cm60 cm60.5 cm61 cm61.5 cm62 cm62.5 cm63 cm63.5 cm64 cm64.5 cm65 cm65.5 cm66 cm66.5 cm67 cm67.5 cm68 cm68.5 cm69 cm69.5 cm70 cm70.5 cm71 cm71.5 cm72 cm72.5 cm73 cm73.5 cm74 cm74.5 cm75 cm75.5 cm76 cm76.5 cm77 cm77.5 cm78 cm

5) Nose length - - - 4 cm4.5 cm5 cm5.5 cm6 cm6.5 cm7 cm

6) Nose base - - - 2 cm2.5 cm3 cm