How to set XLSX cell width with EPPlus?

I find that setting the column widths after I have filled in all the data on the sheet works:

ws.Column(1).Width = 50;

There is also the autoFitColumns method but this ignores cells with formulas and wrapped text so it did not work for me.

ws.Cells["A1:K20"].AutoFitColumns();

Actual Answer is already marked thats the right way of setting column width but there is one issue that is when document is opened first time in excel, it recalculates columns' width (dont know why) so as i mentioned in comment below the marked answer when i set column width to 7.86 its resets it to 7.14 and 10.43 to 9.7x.

i found following code from this epp reported issue to get the closet possible column width as desired.

//get 7.14 in excel
ws.Column(1).Width = 7.86;

//get 7.86 in excel
ws.Column(1).Width = GetTrueColumnWidth(7.86);

public static double GetTrueColumnWidth(double width)
        {
            //DEDUCE WHAT THE COLUMN WIDTH WOULD REALLY GET SET TO
            double z = 1d;
            if (width >= (1 + 2 / 3))
            {
                z = Math.Round((Math.Round(7 * (width - 1 / 256), 0) - 5) / 7, 2);
            }
            else
            {
                z = Math.Round((Math.Round(12 * (width - 1 / 256), 0) - Math.Round(5 * width, 0)) / 12, 2);
            }

            //HOW FAR OFF? (WILL BE LESS THAN 1)
            double errorAmt = width - z;

            //CALCULATE WHAT AMOUNT TO TACK ONTO THE ORIGINAL AMOUNT TO RESULT IN THE CLOSEST POSSIBLE SETTING 
            double adj = 0d;
            if (width >= (1 + 2 / 3))
            {
                adj = (Math.Round(7 * errorAmt - 7 / 256, 0)) / 7;
            }
            else
            {
                adj = ((Math.Round(12 * errorAmt - 12 / 256, 0)) / 12) + (2 / 12);
            }

            //RETURN A SCALED-VALUE THAT SHOULD RESULT IN THE NEAREST POSSIBLE VALUE TO THE TRUE DESIRED SETTING
            if (z > 0)
            {
                return width + adj;
            }

            return 0d;
        }