how much should be dart width for a circular bag

I am making a circular bag.Now i have reached the stage of creating a base for the purse.I am going to put darts..........anybody has any idea as to how wide & long the darts should be???
Thank for your help

I remember U-Handbag does a dart in a circular bag: http://u-handbag.typepad.com/uhandblog/2007/03/silk_pleated_da.html

She uses a 3.5cm length dart with a 55 degree triangle.
I know that this really varies from purse to purse so you could start with these measurements then increase or decrease to your preference.

Good luck!

thanks irene:)
i experimented a bit &  it turned out just fine:)
will chk out the link you have posted now
thanx:)