Decimal odds and American odds are figured differently at the line where 2.00 = +100.
If decimal odds = D and American odds = A,
Decimal odds between 1.01 and 1.90:
A=-(1/(D-1))*100
Decimal odds of 2.00 and greater:
A=(D-1)*100
Negative American odds:
D=1-100/A
American odds of +100 and greater:
D=A/100+1