GST may be calculated easily with the help of below link.
if Management fee is Rs 100 (Inclusive of gst ) then 84.7455 is actual management fee and rest is gst.
₹ 10 inclusive of GST = 8.47
₹ 15 inclusive of GST = 12.71
₹ 20 inclusive of GST = 16.95
₹ 50 inclusive of GST = 42.37
₹ 100 inclusive of GST = 84.75
₹ 200 inclusive of GST = 169.49
How to calculate 18% inclusive of gst -
Say we want to charge ₹ 15 as management fee including gst then
15 x 100 / 118 = 12.7118 is the taxable value(Management fee)
18.71*18% = 2.2878 is the gst amount on 12.71
Total amount = 14.9996 = 15 squared off