This is the formula that I derive from, handed down from my mom, who does these sort of things "by feel" rather than to any kind of specification (because she’s too busy).
consider a 1c:2c:1tbsp ratio of water/vinegar/salt.
There’s an excellent guide to pickling ratios which puts a 4% brine at a 1tbsp -> 1cup water ratio. Easy to remember, works for just about everything (as imperial tends to do).
If adding vinegar (not always a great idea, salt brines last longer in the larder), I put in half as much vinegar as water. A ratio like;
This is pretty siginifcantly different than the above recipe, which has a roughly 2:1 vinegar/water ratio.