Retirement planning starts with three numbers: your target, your projected balance at retirement, and the monthly contribution that closes any gap. This calculator projects all three.
A common shorthand is 25× your expected annual spending, invested in a diversified portfolio. Adjust down (aim closer to 3.5% withdrawals) for very early retirements or extra safety margin.
It's a reasonable starting rule of thumb, based on historical US data. Some researchers argue 3.3–3.5% is safer for very long retirements or from low starting yields.
Use real (after-inflation) returns. Historical US stocks average about 7% real; a balanced portfolio 4–6% real. Being conservative reduces the risk of over-optimism.