Fundamentals: Trinity Study, 4% Rule, and Withdrawal Rate

The Trinity Study (Wikipedia) – This is a landmark paper consistently referenced by the FIRE community and is the source of the “4% Rule”. There’s a lot written about it online and this short WP entry will help get you started.

Analysis of the Trinity Study (The Poor Swiss) – This article is a great follow up to the basics in the Wikipedia article. Be sure to check out the link in the comments section for an updated analysis by the author.

Safe Withdrawal Rate Series (Early Retirement Now) – dig into topics like withdrawal rate, sequence of return risk, and challenges to the 4% Rule with Karsten Jeske’s aka “Big ERN’s” 50+(!) post series. This is a tremendous resource to examine once you have a good understanding of the basics. Pace yourself – it’s a marathon, not a sprint.

Calculating and tracking “your number”

As referenced in Episode 4 and elsewhere, calculating the total assets needed to achieve financial independence (FI) is a key step in the FIRE journey. These links will provide further information and tools to help get you started.

App (iOS) and Google Sheets calculator (Next Phase is NOW) – This article and the tools linked here provide a very simple starting point for generating “the number”. All you need to enter is your desired annual spending and your withdrawal rate, and you’ll get the answer.

Personal Capital – A commonly used free tool (they also offer paid consulting) for tracking your various investment accounts and net worth. PC has simple to use account linking to make it a more automated experience.

FIRE Retirement Calculator (Playing With FIRE) – When you’re ready to start modeling in more detail this is a good next step. This easy-to-use tool allows you to look at the impact of some additional factors, such as asset allocation and expected rate of return.

Simulation tools

Our discussion in Episode 4 included mention of several tools used to model the likelihood of success of a given FI target using methods including Monte Carlo analysis. Here are a few of the many options out there for you to consider.

cFIREsim – This popular tool is the “Crowdsourced Financial Independence and Retire Early Simulator”. cFIREsim is among our favorite sites for performing Monte Carlo analysis of a given FIRE strategy. While you can get started with just a handful of simple parameters, this site is extremely flexible and will allow you to do more complex modeling if that is of interest.

New Retirement – Jason really likes this platform and more people on Reddit seem to be discussing this comprehensive retirement planning tool as well. They have a very full-featured free offering (sign up here) as well as a modestly priced paid “PlannerPlus” version with a host of really nice features (14 day free trial here), as well as consulting services. Be sure to check out their Monte Carlo analysis, which is a different approach than cFIREsim, and therefore is a nice complement to it. There’s a very active Facebook community as well.

The Best Retirement Calculators (Can I Retire Yet) – This is the granddaddy of lists of retirement calculators and simulation tools. Darrow has reviewed many tools over the years and this is a great resource for those seeking info about the options out there.


You Need a Budget (YNAB) – In our opinion, there is no budgeting tool more widely discussed, nor with a user base so passionate than YNAB. If manual spreadsheets aren’t your thing, or you’ve struggled with budgeting, look no further. YNAB has a free 34-day trial and the $84 readily pays for itself. Jason has been using YNAB for several years now and still can’t stop singing its praises! (affiliate link – a free month for each of us if you sign up!)

Mapped Out Money – Nick True is widely regarded as one of the best YouTube resources for zero-based budgeting and in particular, for his YNAB videos. If you’d like to get started with budgeting and this is your first foray – or you’ve struggled before, look not further!

The Best Budgeting Tools to Reach FI (How to FIRE) – If you’re interested in budgeting and want a more comprehensive view of the free and paid options available, this is a good summary of the landscape.