Savings Bridge Years Calculator
Find how many years a cash or savings bridge will last while you draw it down — accounting for the return it still earns.
How it works
If withdrawal ≤ balance × return: never depletes · Else years = ln( W ÷ (W − balance×r) ) ÷ ln(1 + r) · (r = 0: years = balance ÷ W)
A savings bridge is a pot of money you draw down to cover a gap — early-retirement years before a pension starts, a career break, or a sabbatical. Because the balance keeps earning a return while you withdraw, it lasts longer than simply dividing the balance by the withdrawal. If the annual return exceeds your withdrawal, the fund is self-sustaining and never runs out.
Worked example
A $200,000 bridge earning 3% while you withdraw $30,000/year: interest is $6,000, so you net-draw against a shrinking balance. The closed-form gives ln(30,000 ÷ 24,000) ÷ ln(1.03) ≈ 7.5 years — about 7 years 7 months, longer than the 6.7 years you would get ignoring growth.
Frequently asked questions
Why does the fund last longer than balance ÷ withdrawal?
Because the money still earns a return while you spend it. Each year’s interest offsets part of the withdrawal, so the balance falls more slowly than a flat division would suggest.
What does "lasts indefinitely" mean?
If your annual withdrawal is less than the interest the fund earns, the balance grows even as you draw from it, so it never empties. That is the same principle behind a perpetual safe withdrawal rate.
Should I use a real or nominal return?
If your withdrawal stays flat in today’s dollars, use a real (after-inflation) return so the result reflects purchasing power. If your withdrawal is a fixed nominal amount, a nominal return is fine.
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Educational estimate, not financial advice.