How calculations are done — methodology and influences
Free and premium financial calculators are offered for retirement planning and for building a solid financial foundation. The tools are built to be transparent, educational, and useful for exploring your own scenarios. They are not a substitute for professional advice.
Inputs, tax settings, growth rates, withdrawal rules, and time horizons are shown so you can understand what drives the result.
Free tools are designed to answer one focused planning question before you decide whether deeper analysis is worthwhile.
Save, compare, export, and discuss scenarios with a qualified professional when the decision has real financial consequences.
Start free: Choose the question closest to your situation, enter your numbers, and read the result summary before exploring the detailed tables.
Go deeper when it helps: Calculator Premium adds saved scenarios, comparisons, exports, extended projections, and plain-English explanations on supported tools. Journey is a separate guided retirement-planning product.
Check the limits: A result is only as useful as its inputs and assumptions. Change the assumptions, compare another scenario, and treat the output as an estimate—not a promise.
Standard, well-established concepts from retirement and financial planning are used. These ideas are part of the shared intellectual commons—used by researchers, planners, and other tools. No claim is made to have invented them. Examples include:
These concepts are implemented with our own assumptions, design choices, and explanatory framing. The code, user experience, and the way multiple calculators are combined into one suite are original to this site.
The work is inspired by the broader ecosystem of retirement planning—academic work, practitioner tools, and the many people who have contributed to how savings, Social Security, taxes, and spending in retirement are thought about. No one product’s code, interface, or proprietary methods are copied. Monte Carlo simulation is currently implemented in the Retirement Plan Builder and Plan Success tools using published approaches and our own implementation.
You are not required to take our word for it: the calculators are designed so you can see the inputs and outputs and use them to inform conversations with qualified professionals.
Results from these calculators are estimates based on the information you provide and assumptions about future conditions. For the full legal disclaimer, see Disclaimer.