What is Retirement Calculator?
A retirement calculator evaluates whether your current savings rate and investment returns will generate sufficient capital to replace your working income throughout your golden years without outliving your portfolio.
How to Use This Calculator
- Input your current age and planned retirement age.
- Enter existing balances in 401(k), IRA, or other accounts.
- Specify how much you save each month.
- Review your projected total nest egg at age 65 and sustainable monthly retirement income under the 4% safe withdrawal rule.
The Mathematical Formula & Variables
Variables Definition
| Symbol / Variable | Name | Description |
|---|---|---|
t |
Years to Retirement | Retirement Age - Current Age. |
4% Rule |
Safe Withdrawal Rate | Historically proven annual withdrawal percentage that sustains portfolio longevity. |
Step-by-Step Worked Example
Scenario: Age 35 with $50,000 saved, investing $800/month until age 65 (30 years) at 7.5% annual return.
- 30 years of compounding on initial $50,000 = $437,748.
- 30 years of $800 monthly contributions at 7.5% = $984,102.
- Total nest egg at age 65 = $437,748 + $984,102 = $1,421,850.
- Annual safe withdrawal (4%) = $1,421,850 * 0.04 = $56,874.
- Monthly retirement income = $56,874 / 12 = $4,739.50.
Result: At age 65 your nest egg reaches $1,421,850, supporting $4,740/mo in retirement income.
Frequently Asked Questions
What is the Trinity Study 4% rule?
The Trinity Study demonstrated that withdrawing 4% of your portfolio in year one of retirement and adjusting that dollar amount for inflation each subsequent year had a 95%+ success rate of lasting at least 30 years without running out of money.
Should Social Security be counted in my retirement plan?
Yes. Social Security provides inflation-protected baseline income that reduces the total withdrawal demand on your personal investment portfolio.
