Some general considerations are given about the shape of backed-off milling cutters. When the back-off curve is given, one of the three shapes of profile, wanted profile and shaving surface can be found, provided the other two are known. A formula is derived for the case where two of the three above mentioned figures are either straight or plane and the back-off curve is a logarithmic or an Archimedic spiral: tan ∈=tan δ (1-tan α tan γ), with ∈ the wanted profile angle, δ the profile angle, α the back-off angle and γ the shaving angle.