Retirement calculator with Social Security and pensions
Guide · By Kevin Lan · Updated September 2026
Social Security and pensions don't start on day one, so they change your plan in a specific way: once that income begins, your portfolio only has to cover the gap, which can move your retirement date earlier.
Why the timing matters
Social Security and most pensions begin years after an early retirement, so they only offset your expenses from their start year onward. Before then, your portfolio carries the full load; after, it carries what's left. A calculator that simply subtracts Social Security from your expenses gets the early and most demanding years wrong.
Time-phased income is the accurate way
The correct approach models each income stream with a start year and an amount, and reduces the required withdrawal only from that year forward. Because the portfolio no longer has to fund those later years alone, your FIRE number can fall and your date can move sooner, often meaningfully, since later income is exactly what a long retirement leans on.
Approximating it yourself
Without time-phased inputs you can still get close: plan primarily for the bridge, the portfolio-only years between retiring and the year your Social Security or pension starts, and treat later income as a cushion. It's a rougher estimate; a model that phases the income in by year is more precise.
When to claim Social Security
The start age you plan around is itself a decision. You can claim reduced benefits as early as 62, full benefits at your full retirement age (67 for anyone born in 1960 or later), or delay to 70 for delayed-retirement credits worth roughly 8% a year, about 24% more than your full benefit. Claiming early means more years of smaller, inflation-adjusted checks; delaying means fewer years of larger ones, which doubles as longevity insurance. There's no universal answer; it turns on your health and family longevity, your other income, and whether you need the money sooner. For planning, model the start age you actually expect: a later claim means the portfolio funds a longer bridge, an earlier one a shorter but leaner one.
Add it in the app
The calculator below sizes your FIRE number and date from your investments for free. The iPhone app's pension and Social Security planning is time-phased, with each stream starting in the year you choose, so the projection reflects income that arrives later.
References
- U.S. Social Security Administration. Retirement benefits: the effect of early or delayed claiming on your benefit amount. ssa.gov
- Bengen WP. Determining withdrawal rates using historical data. Journal of Financial Planning. 1994;7(4):171–180. The paper that introduced the 4% withdrawal guideline.
- Investopedia. Financial Independence, Retire Early (FIRE): a definition. investopedia.com
FIRE calculator
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Frequently asked questions
Should I include Social Security in a FIRE plan?
Yes, but phased in at its start age rather than assumed from day one. For an early retirement, the demanding years are before Social Security begins; modeling it from the correct year keeps those years honest and can lower the total you need.
Should I take Social Security at 62 or wait until 70?
It depends on your health, longevity expectations, and other income. Claiming at 62 gives more years of smaller checks; waiting to 70 earns delayed-retirement credits of about 8% a year (roughly 24% more than your full benefit) and acts as longevity insurance. There's no universal right answer; model the start age you actually expect.
How does Social Security change my FIRE number?
It reduces the spending your portfolio must cover from the year it starts, so the portfolio needs to fund mainly the bridge years plus any remaining gap afterward. That can lower your FIRE number and pull your retirement date earlier.
When does Social Security start?
In the U.S. you can claim reduced benefits as early as 62, full benefits at your full retirement age (67 for those born in 1960 or later), and the maximum by delaying to 70. A pension's start age is set by its plan.
