Decimal Data Type Problem

 I have calculated values such as ;

OP1:      0,8625
OP2:      31
OP3:      0,965034965034965
OP4:      0,8625
OP5:      0,85
OP6:      0,931506849315068
OP7:      31
MOV1 :  9,02903225806451
MOV2:   8,68387096774194

I have a SQL database table where I defined all data fields decimal(18,2) for these valuesHere is my code ; 

Dim conn As SqlConnection = New SqlConnection("Data Source=SERDARSQLEXPRESS;Initial Catalog=Borsa;Integrated Security=True")
Dim sql As String = "UPDATE StockParametre SET OPT1 = @opt1, OPT2 = @opt2, OPT3 = @opt3, OPT4 = @opt4, OPT5 = @opt5, OPT6 = @opt6, OPT7 = @opt7, MOVY = @mov1, MOVD = @mov2 WHERE Stock = @TickerKod"
Dim cmd As SqlCommand = New SqlCommand(sql, conn)cmd.Parameters.AddWithValue("@opt1", op1)
cmd.Parameters.AddWithValue("@opt2", op2)
cmd.Parameters.AddWithValue("@opt3", op3)
cmd.Parameters.AddWithValue("@opt4", op4)
cmd.Parameters.AddWithValue("@opt5", op5)
cmd.Parameters.AddWithValue("@opt6", op6)
cmd.Parameters.AddWithValue("@opt7", op7)
cmd.Parameters.AddWithValue("@mov1", mov1)
cmd.Parameters.AddWithValue("@mov2", mov2)
cmd.Parameters.AddWithValue("@TickerKod", TickerKod)

conn.Open()
cmd.ExecuteNonQuery()
conn.Close()

When I run these code I have the fallowing error..

The incoming tabular data stream (TDS) remote procedure call (RPC) protocol stream is incorrect. Parameter 3 ("@opt1"): The supplied value is not a valid instance of data type float. Check the source data for invalid values. An example of an invalid value is data of numeric type with scale greater than precision..blabla ...

I tried

cmd.Parameters.AddWithValue("@opt1", FormatNumber(CDec(op1), 2))

but I have the error

Error converting data type nvarchar to numeric.

Thanks