Coast FIRE Calculator with Social Security
Guaranteed income in retirement means you don't have to fund every dollar yourself. Account for Social Security or a pension to get a lower, more realistic Coast FIRE number.
Coast FIRE Calculator
Discover if your current savings are enough to grow to your retirement goal without additional contributions. Get instant, accurate calculations with no signup required.
How it changes the math
Normally your FIRE number is annual spending divided by withdrawal rate. When you expect guaranteed income, only the gap needs funding: (spending - guaranteed income) divided by withdrawal rate. A smaller FIRE number means a smaller Coast FIRE number - and an earlier date you can stop saving.
To model it above, enter the spending you need to cover yourself: total annual retirement spending minus your expected annual Social Security or pension income.
A worked example with Social Security
Suppose you expect to spend $50,000 a year in retirement and anticipate $20,000 a year from Social Security. You only need your portfolio to cover the remaining $30,000. At a 4% withdrawal rate that is a $750,000 FIRE number instead of $1,250,000 - a difference of half a million dollars in what you need to accumulate. Discount that smaller target back to today and your Coast FIRE number drops just as sharply, pulling forward the date you can stop saving.
To model this above, simply enter $30,000 - your spending net of guaranteed income - as your annual retirement spending. The result is a Coast FIRE number that already accounts for your benefit.
Where to find your benefit estimate
Do not guess at your Social Security income. In the United States, you can see a personalized estimate of your future monthly benefit by creating a free account at ssa.gov, which bases the figure on your actual earnings record. Your benefit depends on how much you have earned and the age at which you claim - claiming later, up to age 70, increases the monthly amount. Use a figure that matches your expected claiming age.
Pensions and other guaranteed income
Social Security is not the only income that lowers your number. A workplace pension, an annuity, rental income, or any other reliable stream works the same way: subtract its annual amount from your retirement spending before calculating, because your portfolio only needs to fund what those sources do not. The more of your spending that is covered by guaranteed income, the smaller the nest egg - and the Coast FIRE number - you need.
Should you count on it? The case for caution
Many people in the FIRE community deliberately leave Social Security out of their calculations and treat it as a margin of safety rather than a foundation. The reasoning is that benefit levels decades away carry political and personal uncertainty, and a plan that works without Social Security is more robust. A sensible middle path is to include a conservative fraction of your projected benefit - enough to reflect reality without betting your retirement on an optimistic figure.