When I had a larger cow herd, I hoped for about a 85% calf crop.  This allowed for about  7% open at preg test time and about 7% death loss from then until weaning the next fall.  I did not include cows that were intended to be culled.  When I had about 400 cows, if I weaned 360 calves I felt pretty darn good, although I always thought I should have done better.  It takes about 20% of your calf crop just to maintain your herd, unless you start out with all young and real good cows.