FigureBeacon calculators are designed to answer a narrow question with transparent assumptions rather than imitate a full financial plan.
The calculator projects current retirement savings from the current age to the retirement age using annual contributions and an annual real return, meaning a return assumption after inflation. Contributions are modeled at the end of each year. The projected retirement balance is multiplied by the withdrawal-rate assumption and divided by 12. Expected monthly Social Security and other guaranteed income are then added. That estimated income is compared with planned monthly retirement spending.
All income and spending inputs should be entered in today’s dollars. Results are estimates. The model does not simulate taxes, market volatility, sequence-of-returns risk, longevity, healthcare shocks, required distributions, or future changes to government benefits.
Try several plausible inputs rather than treating one result as a forecast. Changing one assumption at a time makes it easier to see what drives the result.