Math Doesn’t Have an Agenda.
You Do.
The biggest financial question isn’t whether to invest or pay off debt. It’s knowing your exact break-even number — adjusted for inflation and taxes. We built the tools to find it.
Pay Off Debt vs Invest Calculator
Model the real trade-off between investing and paying off fixed-rate debt — mortgages, personal loans, or any fixed obligation. See the 20-year net worth impact, not just a monthly payment figure.
- Inflation-adjusted real return modeling
- Marginal tax rate impact on net gain
- Break-even investment return calculator
- Side-by-side 20-year wealth projection
Student Loan Payoff vs Investing Calculator
Analyze whether paying down student debt faster beats investing the difference. Handles federal and private loans, tax deductibility of interest, and inflation erosion of loan burden over time.
- Federal & private loan tax treatment
- Effective real interest rate after deduction
- Inflation erosion of fixed loan principal
- Profession-specific scenarios (MD, JD, RN)
From your numbers to a clear answer
Enter your situation
Loan balance, rate, term, monthly surplus, tax bracket, and expected investment return. Every input changes the result — no black boxes.
See the real math
We apply the Fisher equation for inflation adjustment, marginal tax modeling, and full amortization — not simplified approximations.
Compare scenarios
Toggle between pay-off-early, invest-the-difference, and do-nothing scenarios side by side over 5, 10, or 20 years.
Decide with confidence
Your result includes the break-even investment return — the exact threshold where the math flips. That’s the number that matters.
Independent Modeling. No Hidden Agenda.
Most financial calculators show you a number without explaining the math. PayoffVsInvest is built differently: every formula is documented, every assumption is visible, and every result is reproducible. We don’t tell you what to do. We show you what the math says — and let you decide.
Read the Methodology →Your numbers never leave your browser.
Every calculation on this site runs in your browser using client-side JavaScript. When you type your mortgage balance or income, that number is processed locally — it is never sent to our servers, stored in a database, or transmitted anywhere.
Unlike AI tools that may use your inputs for model training, or ad-supported sites that may pass data to financial partners, this site cannot access your inputs even if it wanted to. The architecture makes storage impossible, not just against our policy.
We use Google Analytics for anonymous page-view statistics only. Financial inputs are never captured by any tracking script.
Decision Guides
View Research Library →How Inflation Erodes Fixed-Rate Debt: A 2026 Strategic Analysis
See how sustained inflation reduces the real burden of fixed-rate mortgages and student loans — and how to model the effective real interest rate in a high-CPI environment.
Frequently Asked
Should I pay off my mortgage or invest in 2026? ▼
It depends on your mortgage rate versus the real investment return you can realistically earn after inflation and taxes. If your after-tax mortgage rate exceeds your real expected return, paying off debt wins mathematically. Our calculator finds your exact break-even threshold.
Is it better to pay off student loans or invest? ▼
Federal student loan interest can be tax-deductible, which lowers the effective rate. The optimal decision depends on your loan rate, deductibility, tax bracket, and expected real investment returns. Our student loan calculator handles all of these variables simultaneously.
Are my financial inputs stored or tracked? ▼
No. All calculations run in your browser using client-side JavaScript. Your numbers are never sent to a server, saved to a database, or transmitted to any third party. The architecture makes this technically impossible — it’s not just a policy statement.
How is this different from other financial calculators? ▼
Most major financial calculator sites are advertising-supported platforms. Their tools are designed to surface financial product recommendations — the math serves the business model. PayoffVsInvest has no financial partners. We also use inflation-adjusted real-return modeling and marginal tax impact, which most competitor tools omit entirely.
What formulas does the calculator use? ▼
We use standard loan amortization formulas, the Fisher equation for real vs. nominal return adjustment, and marginal tax rate modeling for after-tax interest cost. Every formula and assumption is documented on our Methodology page.
Disclosure: This platform provides mathematical modeling and informational analysis only. It does not constitute personalized financial advice. All projections are estimates based on user inputs and economic assumptions. Calculations run locally in your browser — no financial data is transmitted or stored. We may earn affiliate commissions at no additional cost to you. View full disclaimer.