Different questions
A savings target, an income score, and a depletion projection are not the same output.
Retirement assumptions
Why retirement calculators disagree
Different answers do not always mean one tool is wrong. They often mean the tools are asking different questions, using different assumptions, or showing different kinds of results.
The number is only as useful as what sits behind it.
When two tools show different results, the first question is not “Which number should I trust?” Start by asking what each tool included, what it assumed, and what it measured.
Different assumptions
Spending, inflation, returns, taxes, and longevity can move the result.
Different definitions
“Success,” “income,” and “lasting” can each mean different things.
Visible work helps
You can make a better comparison when the inputs and rules are available to inspect.
01Why they differ
Common reasons two retirement projections can show different paths.
Different inputs can produce different answers.
They answer different questions
One tool may estimate how much to save. Another may test whether money lasts. Another may score income replacement. Those are not the same result.
They use different dollar views
A projection shown in future dollars can look much larger than the same plan shown in today's dollars. Both can be valid if the tool explains the view.
They model spending differently
Flat annual spending, flexible spending, stage-based retirement expenses, and one-time costs can produce very different paths.
They treat taxes and withdrawals differently
Withdrawal order, Social Security taxation, capital gains, RMDs, state taxes, and Medicare surcharges can change the net result.
02What to compare
The assumptions most likely to change the path or the number at the end.
Look for the assumption before judging the result.
A projection is sensitive to small choices. Compare the same choices first, then decide whether the difference is useful information or simply a different model of the question.
Social Security claim age
Claiming before, at, or after full retirement age changes the monthly benefit for life.
Spending
Small monthly spending changes compound across decades of retirement.
Inflation and returns
Nominal returns, real returns, historical replay, and Monte Carlo simulations answer different risk questions.
Taxes and IRMAA
Taxable withdrawals, RMDs, capital gains, state tax, and Medicare surcharges affect spendable cashflow.
Pensions
Start age, COLA treatment, state tax, and survivor continuation can materially change household income.
Planning horizon
A plan tested to age 90 is different from a plan tested to age 100.
03How to read it
Three questions that make a difference easier to understand.
Compare like with like.
Is it answering the same question?
A percentile benchmark, an income-replacement score, a percentage of modeled trials without depletion, and an ending-balance projection are different measures. Do not treat them as interchangeable.
Are the dollars and time horizon the same?
A future-dollar projection can look much larger than the same path in today’s dollars. A plan tested to age 90 is also different from one tested to age 100.
Are the rules and timing the same?
Claiming age, Social Security taxation, RMDs, capital gains, state tax, Medicare surcharges, and withdrawal order can all change spendable cash flow.
04What Retireomics shows
A clearer way to inspect the assumptions behind a modeled result.
Make the difference easier to review.
Assumptions driving the result
Retireomics shows the retirement year, spending, claiming age, balances, return assumptions, taxes, healthcare, and pension settings behind the modeled projection.
Tradeoffs worth comparing
Compare timing, Social Security claiming ages, household scenarios, spending, withdrawals, tax pressure, and Medicare-related costs under the same stated assumptions.
A report you can question
The goal is not a magic number. It is a checkable planning illustration you can review with your spouse or a qualified professional before taking action.
Use differences as questions, not verdicts.
Retireomics is an educational retirement decision model, not financial, investment, tax, legal, Social Security, Medicare, insurance, or fiduciary advice. Its projections are based on your inputs and stated assumptions; they are not forecasts, guarantees, or instructions about what you should do.
This page references selected public IRS, SSA, CMS, and Medicare materials. Retireomics is a private tool, not affiliated with or endorsed by any government agency. See the Methodology for the model’s assumptions and limits.
Sources and examples.
These links help explain the kinds of assumptions and definitions that can differ across retirement projections.
Make your next comparison clearer
Start with a model that shows its work.
Read the methodology, or enter your own numbers and inspect the result.
Read the methodologyStart your plan