"I'd like to retire early" is a wish, not a plan, and the gap between the two is just arithmetic nobody enjoys doing by hand. Early retirement isn't a single age — it's whatever point your savings can carry you from, and that point moves every time you change how much you put away. The useful thing isn't the dream; it's seeing the actual year it becomes possible.
This calculator does that sum for you. Enter your age, savings and contributions, pick a return and an inflation figure, and it projects the earliest age your pot can realistically support, in today's money, then shows whether it survives the full retirement afterwards. The example is pre-filled for a 30-year-old aiming to stop at 50 — nudge the contributions up or down and watch the date shift, which is the quickest way to see what an extra bit of saving actually buys you. The projection is free; the deeper stress-testing is a paid extra. Just try it and put a real age on "early".