The problem is the definition of the intensity of the turbulance.
The UK AIP GEN 3-5 16 gives the interpretations.
LIGHT. IAS fluctuates + or - 5 to 15kts (<0.5g)
MODERATE . IAS fluctuates+ or - 15 to 25 kts (0.5-1.0g)
SERVERE. IAS fluctuates more than 25kts (>1.0g)
There are also discriptions of how it feels.