It requires about 60 or 5 dozen hardboiled eggs to make a gallon of pickled eggs. However it is better to boil 6 dozen eggs because of the differences in size and then if you have an accident when peeling them and you expose the yellow you have some extra boiled eggs to fall back on. Exposing the yellow will cause the vinegar and water to turn cloudy. Also remember that very fresh hardboiled eggs peel like crap. If you'll keep your eggs in the ice box for about 10 - 14 days they will peel easy once hardboiled and shocked in an ice water bath. Fingernail divots in the side of the eggs caused by difficult peeling doesn't hurt anything it just looks un attractive. Snack on the ones you don't pickle, or make egg salad or stuffed eggs instead.
