The “financial independence, retire early” (FIRE) movement has many adherents. But there’s a big difference between having enough money to live in a van down by the river and enough money to live the rest of your life in style. Find out the differences between two approaches: lean FIRE and fat FIRE.

How much is “enough” when it comes to retirement savings? How do you know how much you should be saving, and at what ages, to reach your financial goals? While the answer varies from person to person, some universal rules apply.