12
cups cider vinegar
Poke each pepper several times all the way through with a fork or knife. Combine water, vinegar, salt, and spices including peppers. Boil for 10 minutes and allow to cool to room temperature.
Pour brine mixture over carrots and onions, dividing peppers, oregano, and bay leaves proportionally among jars. Refrigerate.
You've got a big tub of carrots and onions cut up and mixed together. Weigh the whole tub, enter the pounds, and this tells you how much brine to make.
The base recipe makes 24 cups of brine (12 vinegar + 12 water) for 10 lbs carrots plus 3 large onions. Three large onions run about 3 lbs, so the base tub is ~13 lbs of mix → about 1.85 cups of brine per pound. This is the one soft number: onion weight is estimated. If your first batch comes up short or swims, nudge this figure and the whole calculator follows.
Total brine: about 24 cups (1.5 gal). Boil 10 min, cool to room temp, then pour over the tub and divide peppers, oregano, and bay among the jars.