The question of how much emergency cash to carry and in what form is something budget travelers figure out by experience. Here's the analysis.

The cash safety net: carry $200-300 in USD as emergency cash, physically separate from your main wallet. This covers: ATM not working for 2-3 days, card blocked by fraud detection while you sort it out, border crossings with cash-only fees, emergencies in locations without card acceptance.

Why USD: accepted almost everywhere in the world at a known rate. Euros are better in some regions (North Africa, Eastern Europe). Local currency of your home country is less useful unless it's a major global currency.

Storage: a flat money holder in a front pocket, or a hidden pouch in your bag, not a fanny pack (obvious target). Never carry all your cash and cards in one place — split across two locations.

The ATM strategy: withdraw more than you need when you find a fee-free ATM to reduce the number of withdrawals and fees. The Charles Schwab debit card rebates ATM fees globally, making this less critical, but the principle of minimizing transactions still applies.

Card setup: carry at least two cards with separate networks (one Visa, one Mastercard) from different banks. Card networks go down, individual bank systems have issues. Two cards from different institutions mean a single point of failure doesn't leave you stranded.