Living Off Interest Calculator
Estimate whether your portfolio can cover your annual expenses from investment income, and see how much principal you need.
Tip: Include realistic assumptions. A lower return or higher inflation meaningfully increases the required portfolio size.
What does “living off interest” really mean?
Most people use the phrase “living off interest” to mean funding expenses from portfolio growth without permanently shrinking principal. In practice, your portfolio may generate income from interest, dividends, and capital gains. This calculator gives you a practical estimate using your expected return, tax rate, and inflation.
The key idea is simple: your portfolio must produce enough after-tax income to cover spending. If you also want to preserve purchasing power, your return must beat inflation too.
How this calculator works
1) Income your portfolio can generate today
The calculator first estimates nominal (before inflation adjustment) income:
- After-tax return = Expected return × (1 − tax rate)
- Annual income = Portfolio balance × after-tax return
- Monthly income = Annual income ÷ 12
2) Inflation-adjusted sustainability
To estimate whether you can preserve buying power, it calculates a real return:
- Real return = ((1 + after-tax return) ÷ (1 + inflation)) − 1
- If real return is positive, your principal can potentially maintain purchasing power while funding withdrawals.
- If real return is near zero or negative, you may still fund expenses short-term, but long-term purchasing power likely erodes.
3) Required portfolio targets
The calculator provides two portfolio targets:
- Nominal target principal: enough to cover expenses before inflation adjustment.
- Real target principal: enough to cover expenses while accounting for inflation.
Example interpretation
Suppose you spend $60,000/year, expect a 5% return, pay 15% tax on portfolio income, and assume 2.5% inflation.
- Your after-tax return is 4.25%.
- A $1.2M portfolio would generate about $51,000/year after tax.
- That is a shortfall versus $60,000 spending.
- Your required portfolio is higher, especially when inflation is included.
This is why many plans combine portfolio income with flexibility: lower spending, delayed retirement, part-time income, or adjusted return assumptions.
What moves the result the most?
Spending level
Spending is the largest lever. Every recurring dollar of annual expense needs permanent funding. Trimming fixed costs can dramatically reduce your required nest egg.
Return assumptions
Small changes in expected return make huge differences. Be conservative. Using optimistic return estimates may understate required principal and increase risk.
Taxes and account type
Taxable, tax-deferred, and tax-free accounts produce different after-tax outcomes. Keep your estimate grounded in your personal tax situation.
Inflation
Inflation can silently reduce lifestyle over decades. A plan that works in nominal terms may still fail in real purchasing power terms.
Practical guidelines before you rely on investment income
- Build a cash buffer for short-term market volatility.
- Diversify income sources rather than chasing high yield in one asset class.
- Stress test your plan with lower returns and higher inflation.
- Review annually and adjust withdrawals as conditions change.
- Consider healthcare, insurance, and one-time expenses separately.
Final thoughts
A living off interest calculator is a planning tool, not a guarantee. It helps answer two critical questions: “Can my current portfolio support my lifestyle?” and “How much principal do I need for long-term sustainability?” Use conservative assumptions, revisit your numbers regularly, and design a plan that can adapt through different market and inflation environments.