over the course of 100K hands

Big Bets per 100 hands is the common measure.
How do you mean "calculating winrate"? I use Pokertracker.

I did a calculation, based on the formulas given below, using 15BB/100 as SD and 2BB/100 as winrate.

BB possibility of downsizing
125.00 BB 10.83680%
150.00 BB 6.94835%
175.00 BB 4.45514%
200.00 BB 2.85655%
225.00 BB 1.83156%
250.00 BB 1.17436%
275.00 BB 0.75298%
300.00 BB 0.48279%
325.00 BB 0.30956%
350.00 BB 0.19848%
375.00 BB 0.12726%
400.00 BB 0.08160%
425.00 BB 0.05232%
450.00 BB 0.03355%
475.00 BB 0.02151%
500.00 BB 0.01379%
525.00 BB 0.00884%
550.00 BB 0.00567%
575.00 BB 0.00364%
600.00 BB 0.00233%
625.00 BB 0.00149%
650.00 BB 0.00096%