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Coast FIRE Calculator - Free Forever

The day your money
stops needing you.

Coast FIRE is the moment your invested savings will grow into your full retirement number on their own - no more saving required. Find your date. Then decide how you want to live.

4% RULE5% REAL GROWTH$0 MORE CONTRIBUTIONS
THE CALCULATOR

Chart your course.

Six numbers. One horizon. Everything updates live - and everything rides in the URL, so what you make here is what you share.

Coast FIRE inputs

When you'd stop working entirely

Retirement + brokerage, growth assets

In today's dollars

Set to $0 to see pure coast

All math runs in your browser. Nothing is stored or sent.

AGE

YOU'LL HAVE

YOU NEED

$411K$822K$1.23M$1.64M3038455360todayTHE CROSSING · 42
30drag to time-travel60

“From here, every dollar you invest is optional.”

SHARE YOUR SUNRISE

Crossings are meant to be seen.

COAST FIRE CALCULATOR
I CAN COAST AT 42
July 2039 · coast number $289,222
CoastFirewhen can you? - coastfirecalculator.net

The link carries your exact scenario - whoever opens it sees their dawn measured against yours.

THE IDEA

Four truths and a shoreline.

01

The finish line.

Your FIRE number is just your annual spending × 25 (the 4% rule). Spend $50k a year? The finish line is $1,250,000. That’s the whole equation - everything else is getting there.

25 × spend = $1.25M
02

The snowball.

Invested money compounds. At 5% real growth, $1 today becomes $4.32 in 30 years - and the last decade does more work than the first two combined. Time is the ingredient you can’t buy back.

$1.63 · 10y$2.65 · 20y$4.32 · 30y$1 today
03

The coast line.

So the amount you need today is smaller the more time it has to grow: your FIRE number, discounted by time. That falling-toward-you requirement is the coast line - hit it, and compounding finishes the job alone.

$289K today$1.25M at 60
04

The quiet years.

Cross it, and saving becomes optional. You only need to cover the life you’re living - downshift, sabbatical, slow mornings. The market rows the rest of the way.

Read the full Field Guide
RECEIPTS

Show your work.

Finance people check. Good. Here's every line.

FIRE = spend ÷ SWR

$50,000 ÷ 0.04 = $1,250,000

Coast = FIRE ÷ (1+r)^years

$1,250,000 ÷ 1.05^30 = $289,222

Crossing: proj(t) ≥ req(t)

solved monthly → 12y 10m

Assumptions

  • Today's dollars (real returns) - inflation is already netted out
  • Annual compounding, monthly crossing solve
  • End-of-period contributions
  • Constant returns (markets are lumpier - see FAQ)
  • Taxes & fees not modeled
  • SWR applies to the whole FIRE number

Edge cases

Past retirement ageSwitches to "are you funded?" mode
Zero spendPrompts for annual spending
0% returnCoast number = FIRE number
Never crossesShows shortfall + the monthly that would cross
Shared link already crossedGolden hour on arrival

Educational tool, not financial advice. Projections are deterministic simplifications; reality has volatility, taxes, and you.

GO DEEPER

The Coast FIRE Field Guide

Barista vs. coast vs. lean vs. fat. Five levers that move your date. Three people who crossed.

Read the guide
QUESTIONS

Asked at every campfire.

The point where your invested savings, left untouched, will compound into your full retirement number by your retirement age - with zero additional contributions. Past it, you only need to earn enough to cover the life you're living now.