Interactive tool · runs in your browser

When Can I Retire?

A single number like "save 25× your spending" hides all the risk. This runs thousands of randomized market scenarios to estimate the real chance your money lasts.

By Jeremy Lee

Current age

Planned retirement age

Current invested savings ($)

Annual contribution until retirement ($)

Annual spending in retirement ($, today's dollars)what you'll live on each year

Plan until age

Expected real return after inflation

5.0%

Market volatility year-to-year swings

13.0%

—

10th–90th percentile 25th–75th percentile median outcome zero (ran out)

How it works: each simulation plays your life forward one year at a time. Your portfolio grows by a random return drawn from a bell curve around the average and volatility you set, you add contributions until retirement, then withdraw your spending each year after. The success rate is the share of scenarios in which you never run out of money before your plan-until age. This is a teaching tool, not financial advice.

Why a single rule of thumb isn't enough

The famous "4% rule" and "25× your expenses" are averages. But you only retire once, and the order in which good and bad years arrive matters enormously: a crash in your first few retirement years is far more damaging than the same crash twenty years in. Monte-Carlo simulation captures that luck-of-the-draw by replaying your plan across thousands of randomized futures, so instead of a yes/no answer you get a probability — and you can see how much earlier you could retire if you accept a little more risk.