Retirement Calculator Mr Money Mustache

The Mr Money Mustache Retirement Calculator helps you determine how much you need to save each month to achieve financial independence based on the principles outlined by Mr. Money Mustache. This tool uses a simple but effective formula to estimate your required monthly savings based on your desired retirement income and expected investment returns.

How the Mr Money Mustache Retirement Calculator Works

Mr. Money Mustache's approach to retirement planning focuses on achieving financial independence (FI) by saving and investing enough to generate a passive income that covers your living expenses. The calculator implements this philosophy by estimating how much you need to save each month to reach your FI goal.

Key Concepts

Financial Independence (FI) - The point where your passive income equals or exceeds your living expenses
4% Rule - The general guideline that a portfolio needs to generate 4% annual return to support a 4% annual withdrawal rate
FI Number - The total amount of money needed to generate your desired annual income through passive investments

The calculator follows these steps:

Calculate your desired annual income (living expenses)
Determine your desired retirement age
Estimate your expected annual investment return
Calculate the FI Number using the formula: FI Number = Annual Income / 0.04
Determine how many years you have until retirement
Calculate the required monthly savings using the future value formula

The Formula

The core calculation uses the future value formula to determine how much you need to save each month to reach your FI Number by retirement age.

Future Value Formula

FV = PMT × (((1 + r/n)^(nt) - 1) / (r/n)) × (1 + r/n)

Where:

FV = Future Value (FI Number)
PMT = Monthly payment (what we're calculating)
r = Annual interest rate (expected return)
n = Number of times interest is compounded per year (12 for monthly)
t = Number of years until retirement

The calculator also uses the 4% rule to determine the FI Number:

FI Number Calculation

FI Number = Annual Income / 0.04

Assumptions

All calculations assume monthly contributions and monthly compounding
The 4% rule is a general guideline and may not apply to all investors
Expected returns are estimates and may vary significantly
This calculator does not account for taxes, inflation, or other expenses

Worked Example

Let's walk through an example to see how the calculator works. Suppose you want to retire at age 65, have $100,000 in living expenses, and expect a 7% annual return on your investments.

Calculate your FI Number: $100,000 / 0.04 = $2,500,000
Determine years until retirement: 65 - current age (assuming 30) = 35 years
Use the future value formula to calculate required monthly savings:
- FV = $2,500,000
- r = 0.07
- n = 12
- t = 35
PMT = $2,500,000 / (((1 + 0.07/12)^(12×35) - 1) / (0.07/12)) × (1 + 0.07/12)

Calculating this gives approximately $1,250 per month

This means you would need to save about $1,250 per month starting now to have $2.5 million by age 65, assuming a 7% annual return on your investments.

FAQ

What is the 4% rule?: The 4% rule is a guideline that suggests a portfolio needs to generate 4% annual return to support a 4% annual withdrawal rate. This means you can withdraw 4% of your portfolio each year without running out of money.
How accurate is this calculator?: This calculator provides an estimate based on the Mr. Money Mustache principles. Actual results may vary depending on your personal circumstances, investment strategy, and market conditions. It's always a good idea to consult with a financial advisor.
Does this calculator account for taxes?: No, this calculator does not account for taxes. In reality, you would need to save more to account for taxes on your investments and withdrawals. Consider working with a financial advisor to factor in tax implications.
What if I want to retire earlier or later than planned?: The calculator allows you to adjust your retirement age. Retiring earlier will require saving more each month, while retiring later will allow you to save less each month. The key is to choose a retirement age that aligns with your personal goals and financial situation.
Can I use this calculator for early retirement?: Yes, you can use this calculator to plan for early retirement. Simply enter a retirement age that's earlier than your current age plus 30-40 years. The calculator will show you how much you need to save each month to reach your FI goal by that earlier date.