The Retirement Fund Calculator helps you estimate how much money you need for a comfortable retirement.
Factors in inflation, investment returns, and retirement expenses. Calculates the gap between your current savings and your target, and how much you need to save per month starting now.
Disclaimer: Calculations are based on constant assumptions. Actual economic conditions, inflation, and investment returns may differ.
Calculator information
📋 How to use this calculator
- Enter your current age and target retirement age (typically 62-67 in the U.S., depending on Social Security strategy).
- Enter your current monthly expenses in USD; the calculator adjusts for inflation through your retirement age.
- Enter the retirement savings you have already accumulated (401(k), IRA, brokerage, real estate, etc.) as your starting balance.
- Choose an inflation assumption (long-run U.S. average is around 3% per BLS CPI) and an investment return (historical U.S. stocks average about 10% nominal, bonds 4-5%).
- Set your life-expectancy assumption (U.S. life expectancy at birth is about 77.5 years; use 90-95 for a safety margin).
- Click Calculate to see total nest egg required, the funding gap, and the monthly contribution needed.
- Tip: cross-check your number against the 4% safe withdrawal rule.
🧮 Future value annuity + 4% rule
Nest Egg = (Monthly Expenses x (1+i)^n x 12) / 0.04
- i = annual inflation rate (decimal, e.g., 0.03)
- n = years until retirement
- 0.04 = safe withdrawal rate (4% Rule, Bengen 1994)
- Monthly contribution = (Nest Egg - Starting Balance x (1+r)^n) x (r/12) / ((1+r/12)^(12n) - 1)
- r = annual investment return (decimal)
The 4% rule assumes the portfolio sustains a 30-year retirement with a mixed stock-bond allocation.
💡 Worked example: 30-year-old worker, $4,000/month expenses, planning to retire at 65
Given:- Current age = 30, retirement = 65, horizon = 35 years
- Current expenses = $4,000/month
- Inflation = 3%, investment return = 8%
- Starting balance = $25,000
Steps:- Expenses at retirement: 4,000 x (1.03)^35 = $11,260/month.
- Annual need at retirement: 11,260 x 12 = $135,120.
- Nest egg (4% rule): 135,120 / 0.04 = $3.38 million.
- FV of starting balance: 25,000 x (1.08)^35 = $369,000.
- Gap: 3,378,000 - 369,000 = $3.01 million.
- Monthly contribution: approximately $1,310/month for 35 years.
Result: Target nest egg is about $3.38 million; saving roughly $1,310/month into a diversified equity-heavy portfolio gets you there.
❓ Frequently asked questions
How much retirement income should I aim for relative to my final salary?
The SSA and most financial planners suggest a 70-80% income replacement ratio - i.e., retirement income equal to 70-80% of your final working income. A common rule of thumb is to have 10-12x your final annual salary saved by age 65. Social Security on its own typically replaces only about 40% of pre-retirement income, so 401(k), IRA, and taxable savings need to cover the rest.
What is the difference between 401(k), IRA, and Roth IRA?
A 401(k) is an employer-sponsored plan with pre-tax contributions (2025 limit: $23,500, plus $7,500 catch-up at 50+); many employers match a portion. A traditional IRA is an individual retirement account with pre-tax contributions (2025 limit: $7,000, $8,000 at 50+) subject to income limits if you have a workplace plan. A Roth IRA uses after-tax contributions but grows tax-free and withdrawals in retirement are tax-free, subject to MAGI phase-outs.
How does inflation affect retirement savings?
With long-run U.S. inflation around 3%, $1,000 today buys only about $356 worth of goods in 35 years. That is why parking everything in a savings account at 4% APY barely keeps pace with inflation. Historical U.S. stock returns (S&P 500, 1928-2024) average roughly 10% nominal and 7% real, comfortably beating inflation. The Federal Reserve targets 2% long-run PCE inflation.
When should I start saving for retirement?
As early as possible - compound growth depends heavily on time. Example: saving $500/month from age 25 at an 8% return grows to about $1.75 million by age 65. Starting at 35 produces only about $750,000. The Department of Labor and most planners recommend dedicating at least 10-15% of gross income to retirement starting with your first paycheck.
Which instruments fit retirement saving?
Diversify by age: in your 20s-30s, allocate 70-90% to equities (broad index funds like VTI or VTSAX) and 10-30% to bonds. By your 40s-50s, glide toward 60/40. Within five years of retirement, shift toward Treasuries (T-bills, TIPS) and high-grade bonds. REITs and a 5-10% gold allocation can hedge inflation. Avoid speculative bets (single stocks, crypto, FX) for your core retirement pot.
📚 Sources & references
Last updated: May 11, 2026