Cu Parachute – A Retirement Planning App

Developer Bradley McCarthy, an electrical engineer who retired at 46, has developed a very useful app  – iPhone, iPad, and iPod touch devices – for those interested in determining if they are on track to retire comfortably, make adjustments to their withdrawal (decumulation) plan, and track progress as they edge closer to retirement.

The app uses a Monte Carlo simulation to evaluate a user’s probability of having enough money to sustain them in retirement. “What is a Monte Carlo simulation?” you might ask. As noted by Investopedia, Monte Carlo simulations are used to model the probability of different outcomes in a process that cannot easily be predicted due to the intervention of random variables.

Managing a Dynamic Retirement Plan

The app’s users can continuously monitor their retirement income plan status by updating their personalized inputs and re-evaluating their plan. Sensitivity analyses (e.g. how does a change in the estimated tax rate, the years unit retirement, or monthly Social Security benefits impact the chances of success) can easily be performed to better understand how to increase a plan’s probability of success .

A successful retirement income plan will find the balance between not running out of money and living too frugally in retirement. The target success probability in Cu Parachute is between 85% and 100% and will be highlighted with a copper colored background. (Cu is the symbol for Copper on the periodic table.) An 85% probability target would likely be for those who would like to use all of their money during retirement. Conversely, a 100% probability target would be for those wanting to leave most of their money to their heirs.

Soon after downloading the app ($2.99 in the app store) I plugged in my numbers on the Estimation Settings page.

Cu Parachute Estimation Settings

Factors here include inflation rate, tax rate, years until Social Security benefits begin, projected Social Security benefits, pension information, and the number of Monte Carlo simulations you would like to have run.

Cu Retirement Income Plan and Simulation Results

With the estimates established, you plug in other factors including current portfolio value (stocks and bonds), years to retirement, and perhaps most importantly, desired annual retirement income. With all your numbers set, you hit Simulate. The final screen shows your probability of success, the number of iterations that ended with a $0 balance, and the inputs that determined your probability of success.

Final Thoughts

Grab the app today, plug in your numbers and see where you’re at within your retirement plan and your chances of not outliving your money. Make changes to some of your estimates and check out those results. What gives the app its greatest utility is the fact that retirement planning is not a static event. As time passes and your financial picture changes, update your inputs and use the results to make any necessary changes to your plan.


Blogger-in-Chief here at RetirementSavvy and author of Sin City Greed, Cream City Hustle and RENDEZVOUS WITH RETIREMENT: A Guide to Getting Fiscally Fit.


  1. I love this app. I will definitely give this a try.

  2. Thanks for the lead, James! Will definitely be checking it out!

    • Looking forward to getting your feedback, my friend.

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