UPDATE: September 2020: I’ve added the ability to add multiple additional income and expenses streams (with starting and ending dates). Since the calculations are all made in real dollars, these streams are assumed to change along with inflation.
This interactive calculator was built to let you play with the inputs and help you understand how savings rate and retirement spending strongly determine how long it will take you to save up for retirement. Note: it does not simulate the post-retirement period when you start to draw down your savings. That can be done on this post-retirement calculator (Rich, Broke or Dead) which compares the frequency of various outcomes in retirement (running out of money, ending up with way too much money, and life-expectancy).
UPDATE: I’ve added two additional mortality tables for each sex, one representing a very healthy individual and thus longer expected lifespan, and one representing an unhealthy (smoker) individual with a shorter expected lifespan. This provides 3 different life expectancy curves (essentially low, average and high life expectancy). I also upgraded the spending flexibility parameter to allow you to determine at what percentage of your initial balance does the spending reduction kick in.
One of the key issues with retiring is the question of outliving your money. This is also known as Longevity Risk and is especially important if you want to retire early, since your retirement could be 50 years long (or more). This interactive post-retirement calculation and visualization looks at the question of whether your retirement savings can last long enough to support your retirement spending and combines it with average US life expectancy values to get a fuller picture of the likelihood of running out of money before you die.
It helps to answer the question: If I start out with $X dollars at the beginning of my retirement, will I run out of money before I die?