How much Physical cash should one have on hand?

Assuming you have some metals, how much fiat cash do you think one should have on hand? It hurts knowing the cash is becoming more worthless by the day, considering inflation, the hidden tax. My instinct is to put it in metals, and liquidate when needed, but I don't want to put all my eggs in one basket either. What do you guys think? I was thinking 10k is a reasonable amount off the hip, but maybe six months of expenses is a better measure.