Originally Posted by mojotele
Corn sugar is 1.046 pppg while DME is 1.044 pppg. So if you use the formula:
Amount of DME = amount of corn sugar/.9981
That should get you close. The conversion would be the same for table sugar as it is also 1.046 pppg.
To use your example, 1kg of corn sugar would translate to 1.002kg of DME.
EDIT: Totally hosed my math.
I believe the real figures are:
DME 1.046 pppg
Corn Sugar 1.042 pppg
Sucrose 1.046 pppg
LME 1.037 pppg
where pppg is points per lb per gallon
So you would need about 10% more corn sugar than DME to get the same fermentables, or 20% more LME.
If you are talking about small additions (which you are) to adjust a recipe, I agree with mojotele, the differences are pretty insignificant, If the additions are a major component of the fermentables, then the differences can add up.