· Tool · Real Cost
The real cost of a recurring spend.
A small spend repeated for years is also a number. This shows what that recurring spend would be worth over a working life if the same money were invested instead. It shows the math and the assumptions behind it. What you do with that is yours.
What is the real cost?
A recurring spend, seen over a working life, if it were invested instead. We show the math. What you do with it is yours.
Your inputs stay in your browser. Nothing here is stored on a server or sent anywhere. Saved scenarios use local storage on this device only.
The formula, in plain English
- Turn the spend into a monthly number: a daily habit times about 30.4 (365 days across 12 months), a weekly habit times about 4.3, a monthly habit stays as is.
- Each month, add that contribution to the running balance, then grow the whole balance by one month of the annual return (the yearly rate divided by 12).
- To see what you put in, multiply the monthly amount by 12 and by the number of years.
Worked check: $7 a day for 30 years at a 7% assumed return grows to about $261,000, on about $76,650 put in.
Assumptions
- The return is constant every year. Real markets vary; the same long-run average produces a different shape if the early years are weak.
- Contributions are made monthly and start growing the month they are added.
- No taxes, no fees, no inflation. The result is a pre-tax, pre-fee, pre-inflation nominal number.
- The return rate is your input, not a forecast. You change it; it is never a promise of any specific market result.
- A day is treated as 365 / 12 of a month and a week as 52 / 12 of a month, so a daily or weekly habit is annualized evenly across the year.
Limitations
- Constant-return math hides sequence risk. A portfolio that earns one good year and one bad year does not end where a steady average would.
- Inflation lowers the purchasing power of the final number. For an after-inflation view, subtract roughly 2 to 3 points from the return assumption.
- It does not model a specific account, fund, or asset mix, and it does not account for the times you would have spent the money anyway.
- It assumes the recurring spend and the contribution continue uninterrupted for the whole period.
- It is not a forecast. The return is your assumption, not a prediction of any market.
- It is not advice. It does not tell you to stop buying coffee, change a habit, or invest a dollar.
- It is not after-tax or after-inflation. Both reduce the real-world value of the number shown.
- It is not personalized. It knows nothing about your situation; for that, talk to a fee-only fiduciary.
Privacy: this calculator runs entirely in your browser. Your inputs are not stored on a server and are never transmitted. Saved scenarios use local storage on this device only; clearing browser data resets them.
A note on how this was made. Lessons, glossary entries, and articles on ClearMoneySchool are drafted with AI assistance and reviewed by Joseph Citizen before publication. We use AI to draft faster and explain more clearly. We do not use it to publish anything we have not read, fact-checked, and edited. Read our full AI policy.