Invest Your Old Debt Payment
See how much wealth you can build by investing the monthly payment you used to make on debt.
Who This Is For
If you just paid off debt (or are about to), this calculator shows the long-term impact of investing that monthly payment instead of letting lifestyle inflation eat it up. It's a powerful way to turn your debt payoff momentum into wealth building.
Example Scenario
Say you were paying $400/month on debt. Instead of spending that money, you invest it for 20 years at 7% annual returns.
Result: You'd have over $200,000—even though you only contributed $96,000. The difference? Compound growth.
How It Works
This calculator simulates investing a fixed monthly amount over time with compound growth. Each month:
- You invest your monthly contribution
- Your portfolio grows at the expected annual return rate
- Gains compound month-by-month
The result shows your total portfolio value, how much you contributed, and how much came from growth. Optionally adjust for inflation to see purchasing power in today's dollars.
Assumptions and Formula
Assumptions used in this model:
- Monthly contribution is invested consistently with no missed months.
- Return is a constant annualized estimate converted to monthly growth.
- Optional inflation adjustment uses a constant inflation rate.
Core growth formula: next value = (current value + monthly contribution) × (1 + monthly return).
How to Interpret Your Results
| Signal | What It Means | Action |
|---|---|---|
| Growth exceeds contributions early | Compounding is taking over | Avoid contribution interruptions |
| Real (inflation-adjusted) result is much lower | Purchasing power risk is meaningful | Increase contribution growth over time |
| Final value is highly rate-sensitive | Return assumptions dominate outcomes | Plan with conservative and base scenarios |
Educational tool, not financial advice. This calculator provides estimates based on assumptions about future returns, which are not guaranteed. Actual investment returns vary. Consult a financial advisor for personalized advice. Tax implications not included.
Frequently Asked Questions
Deep Dive Guide
Read the Financial Priority Ladder guide
Order of operations for emergency fund, debt payoff, and investing.