Retirement changes the question your portfolio must answer. During your working years the only number that matters is growth; afterward, the portfolio has to produce a paycheck. Dividends from stocks, interest from bonds, and realized capital gains are the three taps that fill that paycheck, and this calculator totals them from a single set of assumptions.

Feed it a portfolio value -- $500,000 is the default -- plus a dividend yield, a bond interest yield, and an expected capital gains rate. With 3 percent dividends, 2 percent interest, and 5 percent gains, the portfolio throws off $50,000 a year, or about $4,167 a month. The tool breaks that into each stream so you can see how much of your income arrives as cash in hand versus paper gains you must sell to realize.

The mix matters as much as the total. Dividends and interest land in your account without selling shares; capital gains require trimming the portfolio, which shrinks next year's base. Retirees who need steady spending money often tilt toward the first two, accepting slower growth for reliability. Adjust the yields to match your actual holdings -- a Treasury-heavy portfolio and a dividend-growth portfolio with the same value can produce very different monthly checks.

With the pre-filled defaults — Portfolio Value $500,000, Dividend Yield 3%, Interest/Bond Yield 2%, Expected Capital Gain Rate 5% — the Investment Income Calculator returns Annual Dividend Income $15,000.00, Annual Interest Income $10,000.00, Annual Capital Gain $25,000.00, Total Annual Return $50,000.00, Average Monthly Income $4,166.67, Effective Total Yield 10.00%. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.