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.
Retirement assumptions
Why retirement calculators disagree
If two retirement calculators give you different answers, it does not automatically mean one is broken. They may be using different assumptions about spending, inflation, Social Security, taxes, healthcare, pensions, investment returns, and how long the plan should last.
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.
The assumptions that move the answer
A retirement projection is sensitive. The useful question is not just what number appears at the end. It is which assumptions pushed the number there.
| Assumption | Why it changes the result |
|---|---|
| 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. |
Why scores can feel contradictory
A percentile benchmark, a replacement-rate score, a Monte Carlo success rate, and an ending-balance projection are different metrics. They may all be useful, but they should not be read as the same answer.
Social Security is a clean example. The Social Security Administration says claiming age affects the monthly benefit amount, and early or delayed claiming adjustments are permanent. A calculator that assumes claiming at 62 can produce a different result than one testing 67 or 70.
Taxes are another example. If one tool uses a flat tax estimate and another models withdrawal order, Social Security taxation, RMDs, capital gains, state tax, and IRMAA, the outputs can diverge even when the starting balances match.
What Kessavo shows instead
Assumptions driving the result
The calculator highlights the retirement year, spending, claiming age, balances, return assumptions, taxes, healthcare, and pension settings behind the selected projection.
Tradeoffs worth comparing
Kessavo is designed around decisions like retire now or later, claim Social Security at different ages, compare spouse scenarios, and review tax or Medicare pressure years.
A report you can review
The goal is not a magic number. The goal is a checkable planning illustration you can discuss before taking action.
Kessavo is an educational planning illustration, not investment, tax, legal, Social Security, Medicare, insurance, or fiduciary advice.
Sources and examples
- Social Security claiming age changes monthly benefits
- USA.gov overview of Social Security benefit calculators
- FIRECalc calculator assumptions and spending options
- FIRE calculator method explanation
- Boldin assumptions documentation
- Boldin pension documentation
- MaxiFi feature overview
- AARP retirement calculator overview
Run a model where the assumptions are visible.
Start with the decision, then inspect the assumptions behind the result.
Start your plan