Which one do you need?
Can I stop saving yet? The Coast FIRE calculator finds the balance that grows into your full number on its own, with no further contributions. Reaching it does not mean you can stop working — it means you can stop saving, which is often the more useful freedom.
What if I work part-time? The Barista FIRE calculator works out the portfolio needed when a job covers part of your expenses, with health insurance as its own line — because in the US it is the cost that most often breaks these plans.
How do I reach my money before 59½? The bridge account calculator sizes the gap between early retirement and penalty-free access, and shows why a Roth conversion ladder makes it far smaller than it first appears.
How much can I actually spend? The Die With Zero calculator finds the maximum constant real spend that finishes at zero — with honest longevity bands showing what happens if you live longer than planned.
Will my plan survive a bad decade? The 4% rule stress test runs the same plan against six return orderings, including an identical crash placed early and late, to show that sequence matters more than average.
Two things these calculators do differently
Real returns, properly derived. Every figure is in today's money, so
it compares directly to today's expenses. The real return uses the Fisher relation —
(1 + nominal) / (1 + inflation) − 1 — rather than subtracting inflation
from returns. At 7% and 3% that is 3.883%, not 4%. Over thirty years the shortcut
overstates the result by more than 3%, which is years of work.
Present values, not multiplication. Working out how much you need to cover fifteen years of spending is not "expenses times fifteen" — the money keeps earning while you spend it. Using the present value of the stream instead cuts the requirement by roughly a fifth at a 4% real return. That single correction is often several years of unnecessary saving removed from a plan.
What these projections are, and are not
They are arithmetic. Each assumes a constant return every year, which no market has ever delivered. They tell you where you stand under stated assumptions and which levers move the answer most — they do not predict the future, and a confident-looking number from wrong assumptions is still wrong.
That is exactly why the stress test exists. Two retirees with identical average returns over thirty years can finish in completely different places depending only on the order those returns arrived. If you read one page here, read that one.