Financial Independence Retire Early Calculator
The is a great little simulation model/calculator to predict whether you are ready to retire/ how much you need to adjust factors to reach your goals.
They ask you to input:
1. Annual Spending
2. Total Savings/Investments
3. How long you will need to live off the numbers.
They then give you a percentage of how likely you are able to succeed (not run out of money) given your current plan.
Below is a link for a more complex crowdsourced FIRE simulator. It will let you add quite a bit more factors (i.e. pension, inflation rate) into your simulation if you have the time/interest.