What is the approximate duration between LH surge and ovulation?

The onset of the gonadotropin surge resulting from increasing estrogen secretion by preovulatory follicles is a relatively precise predictor of ovulation. It occurs 34 to 36 hours before release of the ovum from the follicle. LH secretion peaks 10 to 12 hours before ovulation and stimulates the resumption of meiosis in the ovum with the release of the first polar body. Ref: Cunningham F.G., Leveno K.J., Bloom S.L., Hauth J.C., Rouse D.J., Spong C.Y. (2010). Chapter 3. Implantation, Embryogenesis, and Placental Development. In F.G. Cunningham, K.J. Leveno, S.L. Bloom, J.C. Hauth, D.J. Rouse, C.Y. Spong (Eds), Williams Obstetrics, 23e.