Target Portfolio
The portfolio size needed at retirement to sustain your planned spending. targetPortfolio = annualSpending / withdrawalRate
Finance
About Coast FIRE Calculator
Solo, household, income offsets, and currency presets on one page.
FIREcompound growthretirementsolohouseholdincome offsets
About this calculator
What this does
Calculates the lump sum you need today so that, without adding another dollar, compounding can grow your portfolio to a target retirement balance by your planned retirement age. Also estimates your earliest coast age—the point where your contributions can stop because compounding alone will carry you to your goal.
Who it is for
Anyone pursuing financial independence who wants to know when their investments become self-sufficient. Works for single planners and married couples, and supports pensions, Social Security, and other fixed income streams as offsets against retirement spending.
How it works
The calculator adjusts retirement spending for guaranteed income, applies the safe withdrawal rate to find the target portfolio needed on retirement day, then discounts that target back to today using your real (inflation-adjusted) return to find the coast number. It also projects contributions forward year by year to find the earliest age where the projected balance crosses the coast threshold.
Limitations
Assumes a constant real return every year and ignores sequence-of-returns risk, market volatility, taxes, portfolio allocation shifts, and early withdrawal penalties. The coast number assumes zero additional contributions after reaching coast, which may not reflect what happens in a real market cycle.
Formula
Coast Number
The lump sum needed today so that compounding to retirement equals the target portfolio. coastNumber = targetPortfolio / (1 + realReturn)^yearsToRetirement
Real Return
Inflation-adjusted investment return derived from nominal growth and expected inflation. realReturn = (1 + nominalReturn) / (1 + inflation) - 1
Income-Adjusted Spending
Retirement spending reduced by any guaranteed income that starts on or before retirement. adjustedSpend = max(0, spending - incomeAtRetirement)
How it works
Step 1
Choose your mode
Select Solo for individual planning or Household for joint planning with a shared portfolio and one coast age.
Step 2
Enter your ages
Set your current age, partner age in household mode, and target retirement age to define the compounding timeline.
Step 3
Set your capital
Input your current invested assets, monthly contributions, and expected annual contribution growth rate.
Step 4
Configure market projections
Set your expected nominal return, inflation assumption, and safe withdrawal rate for the retirement phase.
Step 5
Add income streams
Include pensions, Social Security, or other fixed income with their respective start ages to reduce the required portfolio.
Step 6
Review your results
Check the coast number, target portfolio, progress percentage, and earliest coast age to understand your FIRE timeline.
Reference ranges
Withdrawal Rate
4% is the traditional rule for 30-year retirements. 3–3.5% for longer horizons or conservative planning. 5%+ may work with flexible spending or shorter timelines.
Real Return
Historical S&P 500 real return is roughly 6–7%. Conservative planners use 4–5%. Aggressive assumptions go above 8%. Actual yearly returns vary significantly.
Coast Age
Common coast ages range from 35 to 55 depending on savings rate, return assumptions, and spending goals. Younger coast ages require higher savings rates.
Progress Percent
Below 50% means significant future contributions are needed. 50–80% is on track. Above 80% means the coast threshold is near or within reach.