While buying sunscreen recently, most of the NIVEA products had rating in LSF or just the number. Case in point, https://www.nivea.ch/shop/de-ch/nive...085660070.html. I got this one.

Is there any straightforward conversion of LSF ratings to the more standard SPF ones?

Also, is there any difference between sonnencreme and sonnenmilch?

Lsf = spf / 2

LSF == Lichtschutzfaktor (German)
SPF == Sun Protection Factor (English)
FPS == Factor de proteccion solar (French)

Conversion from on to the other: Multiply by 1.

Viscosity. Think of dairy cream and regular milk.
Sonnenmilch is sun lotion, whereas Sonnencreme is sun cream.

Yet, they're equally effective? (for the same SPF / LSF rating)

I'm fairly sure that in Europe at least SPF is the same as LSF, which is really just a German term for the same thing.

Found a few references to US or Aussie standards being slightly different, but nothing concrete.

any reference for this conversion?

Supposedly.

Should have added that i was referring to the American LPF, as for European systems it's just a bunch of different languages with al the same scale.