Compound Interest Monte Carlo Calculator

Use this calculator to project long-term portfolio growth, retirement withdrawals, and inflation-adjusted purchasing power with editable return assumptions.

Long-Term Planning

Compound Interest Monte Carlo Calculator

Model portfolio growth, retirement withdrawals, and inflation-adjusted purchasing power with editable return assumptions and probability outcomes.

Current age Retirement age End age Current portfolio Monthly contribution Contribution growth (%) Inflation (%) Expected return (%) Volatility (%) Simulations Target balance (today's $) Retirement spending Withdrawal rate (%)

Inflation-adjust spending

Probability of success

0% Retirement to end age

Hit target at retirement

0% Chance of meeting the target

Median balance at retirement

$0 $0 in today's dollars

Median ending balance

$0 $0 in today's dollars

Median first-year withdrawal

$0 Retirement income assumption

Median annual contribution

$0 Simulation summary

Retirement balances

Percentile

Nominal

Real

P10

$0

$0

P50

$0

$0

P90

$0

$0

End-of-plan balances

Percentile

Nominal

Real

P10

$0

$0

P50

$0

$0

P90

$0

$0

This is a simplified planning model. It does not include taxes, pensions, Social Security, account-specific rules, or sequence-aware asset allocation changes.

What It Includes

• Accumulation modeling with ongoing contributions
• Retirement drawdown with fixed-spending or percent-based withdrawals
• Inflation-adjusted and nominal balance views
• Conservative, base, and aggressive return presets
• Monte Carlo percentile outcomes and survival probability

Notes

• Results are estimates based on simplified annual simulations.
• Presets are editable shortcuts, not market forecasts.
• Success means the portfolio does not deplete before the selected end age.
• The retirement target compares against inflation-adjusted retirement balances in today’s dollars.