About the Advanced Coast FIRE Calculator

The Advanced Coast FIRE Calculator is a free, open educational tool that helps people in the Financial Independence / Retire Early (FIRE) community visualize when their existing investments will grow large enough to fund retirement — even if they stop contributing. The calculator combines a deterministic compound-growth model with a Monte Carlo engine, life-stage spending changes, and configurable stress scenarios for market crashes, high inflation, and prolonged low-return decades.

Why we built it

Most online FIRE calculators assume a single average return and a single spending level for the next 40 years. Real lives don't work that way: markets are volatile, families grow, salaries change, and inflation arrives in waves. We wanted a planner that lets a thoughtful person model those realities in minutes, get a probabilistic view of success, and share the result with a partner or advisor through a single link.

Methodology

The deterministic projection uses your portfolio allocation, expected returns per asset class, contribution schedule, life-stage spending, and a chosen safe withdrawal rate to compute a baseline trajectory. The Monte Carlo engine runs thousands of randomized return paths against the same inputs and reports the probability your plan survives to your planned end-of-life age. Historical bootstrap and sequence-of-returns simulators stress-test the same plan against actual U.S. market data, including the worst rolling windows on record.

Privacy first

Inputs you type stay in your browser. Sharing only happens when you click the share button, which encodes your numbers into a URL you choose to send. We do not sell user data. Advertising, when shown, follows the consent controls described in our privacy policy.

Not financial advice

This calculator is an educational model, not personalized financial advice. Talk to a fiduciary financial planner before making major decisions about retirement, taxation, or insurance.