Your pension, ISA savings and ongoing contributions, tested age by age: the calculator runs the Hundred Summers app's own earliest-retirement solver, projecting every year of each candidate retirement with UK income tax on withdrawals and the State Pension — and returns the youngest age at which every year funds. Your figures never leave your browser.
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Most retirement-age calculators divide your pot by a spending multiple. This one does what the Hundred Summers app does: for each candidate age it projects every year of your plan — contributions until that age, then drawdown with income tax grossed up properly, the State Pension arriving on schedule, growth compounding on what remains — and asks whether any year fails to fund. A binary search then finds the youngest age where none does.
The result moves honestly with your inputs. More ISA saving buys retirement before pension access; the State Pension toggle shows how much of the answer it quietly carries; the plan-to age prices longevity. If the answer is “not by 74”, the plan needs more saving or less spending — better to know now. Related: how much do I need to retire? and the FIRE calculator.
Hundred Summers