Personal Runway

If you lost your income tomorrow, how long could you survive without changing your lifestyle?

That's your personal runway.

Money you can readily access ÷ normal monthly spending = months of runway.

Use money you can actually draw on, not the value of everything you own. The calculation assumes your spending stays the same and no replacement income comes in.

It tells you how long you have before financial pressure starts making decisions for you.

It doesn't tell you how many months you ought to have. That depends on your circumstances.