To estimate how long your money will last, start by calculating your total savings and monthly spending. Divide your savings by your monthly expenses to get a rough timeline. For example, if you have $30,000 saved and spend $2,000 per month, the money could last about 15 months. A more accurate plan should include inflation, unexpected costs, and income sources like investments or part-time work. Financial planning tools or spreadsheets can help track this. If retirement is the goal, many planners also consider withdrawal guidelines such as the 4% rule.