What gauge jumper cables do I actually need?

Across the reviewers we read, the rough consensus is 6-gauge for compact cars and short reaches, 4-gauge as a flexible daily-driver default, and 1- or 0-gauge for trucks, diesels, larger SUVs, or when you need to reach across a long distance. Lower AWG numbers mean thicker copper and less voltage drop, which matters more the longer the cable and the larger the engine.