Expense Impact Calculator
Turn any monthly expense into the real, inflation-adjusted monthly income you give up at retirement.
A recurring expense, e.g. a subscription or daily coffee habit
Nominal return before inflation; broad stock markets have averaged ~7-10%
Historical average is ~2-3%
The 4% rule is a common rule of thumb
Investing $100/month instead of spending it would buy you this much extra monthly income at age 67, in today's purchasing power — about 3.6× the expense itself, for life.
The True Cost of a Recurring Expense
A monthly expense doesn't just cost its sticker price — it costs everything that money could have become if it were invested until retirement. This calculator makes that trade-off concrete in three steps:
- Invest instead of spend: the expense is contributed every month from your current age until retirement
- Compound at the real rate: growth uses your gross yield minus inflation, so results stay in today's purchasing power
- Convert to income: the final portfolio is turned into monthly income using your withdrawal rate
The headline number is the extra monthly payment, in today's dollars, that you could have for the rest of your retirement. For a young saver, even a modest expense often translates into several times its own size in monthly retirement income.