How to Estimate How Long Your Savings Will Really Last
By the Super Simple Digital Tools Team · Updated June 2026
Knowing the size of your savings tells you very little on its own. What matters is the gap between what the pot earns and what you pull out of it, because that gap is what eats into your principal. This calculator exists to turn three or four plain numbers into a single answer: the date the money runs dry. Before you trust that answer, it helps to understand which inputs are doing the heavy lifting and how to choose them so the result reflects your real situation rather than a hopeful one.
Start with the withdrawal amount, because it dominates everything else. Build it from an actual budget rather than a round number, and include the irregular costs people forget, such as insurance, car repairs, and annual subscriptions. If you withdraw monthly, divide your yearly spending by twelve so the frequency matches reality. A common mistake is entering only fixed bills and ignoring discretionary spending, which makes the timeline look far rosier than your bank statements would.
Next, set the interest or return rate, and lean conservative. The calculator assumes a flat, steady rate, but markets do not behave that way, and a downturn in the first few years of drawdown is especially damaging because you are selling assets while they are cheap. Picking a rate a point or two below your hoped-for average builds in a buffer against that sequence risk. If the money is in plain cash, use the actual savings rate, and remember that anything above the inflation rate is genuinely growing your buying power.
Once you have a baseline answer, run the same scenario two or three more times with different numbers. Try a withdrawal that is ten percent higher to see how fragile your plan is, then try a lower one to find the spending level that keeps the money alive for as long as you need. Toggle the inflation adjustment on, since flat withdrawals quietly lose buying power and an inflation-aware run is closer to the truth. The spread between these scenarios tells you how much margin you really have.
Finally, treat the output as a conversation starter, not a verdict. It cannot foresee a medical bill, a market crash, or a tax change, and it does not replace advice for a high-stakes retirement decision. What it does well is show cause and effect instantly, so you can see exactly how much an extra year of work, a smaller monthly draw, or a better return rate moves your finish line. Revisit it whenever your balance or spending changes, and use it to keep your plan grounded in numbers.
- Base your withdrawal figure on a real budget that includes irregular and annual expenses, not just monthly fixed bills.
- Enter a return rate a point or two below your expected average to cushion against poor early-year returns.
- Turn on the annual withdrawal increase to reflect inflation, since flat withdrawals understate how fast spending power erodes.
- Run several scenarios with higher and lower withdrawals to find the spending level that makes your money last as long as you need.