Personal Finance

Retirement Coast & Milestone Calculator

Calculate your Coast FIRE milestone where compound investment growth fully funds your target retirement portfolio without requiring additional annual savings.

Interactive Web App Open in Google Sheets ↗ Download Excel (.xlsx) ↓
Planning Mode
Choose whether you want to calculate your required retirement age or your safe retirement income.
Timeline
25 yrs
Your current age.
35 yrs
Age when you stop contributing new capital and let growth compound. Cannot precede current age.
65 yrs
Age when you begin drawing from the portfolio. Cannot precede coast age.
Portfolio & Savings
$10,000
Annual savings contributed until reaching Coast Age.
$0
Initial invested assets. The maximum slider limit scales with current age up to $2,500,000 based on top-tier savings benchmarks rounded to the nearest $100,000.
Retirement Goal
$44,000
Desired annual retirement spending in today's dollars.
Assumptions
7%
Expected annual portfolio growth adjusted for inflation (historical market average is ~7%).
4%
Annual percentage withdrawn from portfolio in retirement (Trinity Study benchmark is 4%).
Social Security
$0
Your estimated annual benefit at Full Retirement Age 67 (Social Security statement primary insurance amount). Set to $0 if not including.
67 yrs
Age when you begin receiving benefits (earliest 62 with 30% reduction, full 67, maximum delayed 70).
$0
Spouse's estimated annual benefit at Full Retirement Age 67. Set to $0 if single or not including.
67 yrs
Age when your spouse begins receiving benefits (earliest 62 with 30% reduction, full 67, maximum delayed 70).
Milestone Outcome Milestone Outcome
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Balance at Coast Age
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Projected Balance at Retirement
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Target Nest Egg Needed
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Projected Annual Retirement Income
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Why I Built This: Engineering Career Freedom

In technology careers, burnout frequently peaks just as compensation reaches its height. Coast FIRE is the financial inflection point where your existing retirement balance will grow to full independence on compound returns alone without adding another dollar of principal.

Reaching Coast FI fundamentally changes how you negotiate roles, take career risks, and choose projects because you no longer need to optimize solely for maximum base salary.

Core Mechanics & Assumptions

  1. Doubling Cycles: Based on the Rule of 72 and your configured 7% inflation-adjusted market return, invested principal doubles approximately every 10 years.
  2. The Asymmetry of Early Savings: Front-loading savings into compounding index assets early reduces or eliminates the need for ongoing contributions in your 30s and 40s.
  3. Safe Withdrawal Baseline: Target nest eggs use your configured 4% safe withdrawal rate rule (25 times annual spending).
  4. Social Security Integration: Optional guaranteed income stream reduces required portfolio nest egg based on your and your spouse's Full Retirement Age (FRA 67) benefits and individual claiming ages (62 to 70).
  5. IRS Catch-Up Contribution Expansion: When Current Age reaches 50+, the annual contribution ceiling expands dynamically to include the standard IRS age 50+ catch-up allowance (+$7,500 for 401(k) and +$1,000 for IRA). For ages 60 to 63, the ceiling further expands under SECURE 2.0 super catch-up provisions (+$11,250 for 401(k) and +$1,000 for IRA).

Use the timeline, contribution, assumption, and Social Security controls to locate your exact transition milestone.

Disclaimer: Not Financial Advice
This calculator and accompanying analysis are provided strictly for educational and informational purposes and do not constitute financial, investment, legal, or tax advice. The author is not a licensed financial advisor, professional consultant, or fiduciary. Calculations are mathematical simulations based on hypothetical return assumptions and should not be relied upon for personal financial decisions. Always consult a qualified professional for advice tailored to your situation.
Newsletter Companion

On Retirement

Read the complete article and analytical deep-dive on LinkedIn.

Read Companion Article on LinkedIn ↗