At the right, enter how much you need, how much you have, and how many years you want the plan to last (or the calendar year you want the plan to end). Then click the submit button to view the results in a new window. (Not sure how much you will need? Check the US averages. Not sure how many years to plan for? See Vanguard's longevity calculator for an estimate.)
Without any other information, FIRECalc will assume you want to keep your annual spending about the same for as many years as you specify, you aren't planning on receiving any Social Security or pension, and your retirement portfolio is invested in a "couch potato" portfolio of 75% stock index and 25% bond funds, with a 0.18% fee to the fund. But you can change any or all of those assumptions. You can refine the spending and investment assumptions, explore the impact of some of your decisions, factor in all sorts of exceptions, and/or let FIRECalc search for savings or spending levels that will let you meet your goals. Just click on any of the tabs at the top to enter the optional information.
Each tab will take you to a description as well as the place to enter the optional information, but in short: Start Here is this page, where you enter spending, portfolio balance, and years. Other Income/Spending is where you enter Social Security, pensions, and other yearly adjustments. Not Retired? is where you specify when the plan is to start, and how much you'll add to your portfolio until then. Spending Models lets you select from several approaches to spending during retirement. Your Portfolio allows selection of different investments. Portfolio Changes lets you make lump sum changes to your portfolio at some future year. Investigate allows you to investigate the consequences of some of the other choices you can make in planning your retirement.
All data is preserved as you go among these tabs. You don't need to click Submit until you are finished.