I found several retirement income planning tools on the Internet. Fidelity has one. I really learned a lot from it. Later, for privacy and simplification, and because I got tired of the relentless solicitations for annuities, I created a spreadsheet on my PC and did the budget process offline, removing all my budget and financial information from the web.
The term budget puts many people off. For this exercise, budgeting is about determining current and retirement expenses, not starving or going without. While this budget information could be used to modify spending, the real purpose is to discover how much money will be needed
in future years.
I think most budget efforts are too complicated. With a few simplifications, it can be fairly simple. On a spreadsheet, to produce a budget for a year, put the months across the top and expense categories down the side. To determine initial amounts, I added our expenses, by category, from the previous year's check register. I settled on these categories:
Her credit cards, My credit cards, Cash, Dental, Medical, Gifts, Insurance, Mortgage, Tax, Travel & entertainment, Utilities. Pick categories that work for you.
It then becomes very easy to create a budget for future years.
For those who need more income in retirement than Social Security provides, read Steven Vernon's book, Money for Life. The short version is that he suggests 3 alternatives, a small immediate fixed annuity, manual systematic withdrawals, or a mutual fund that provides automatic withdrawals (Managed Payout Fund). Jane Bryant Quinn's excellent book How to Make Your Money Last describes the very few cases in which an annuity may be justified.