How to choose a retirement planning tool: seven questions
Most retirement tools describe themselves the same way: thousands of simulations, your personal number, a plan you can trust. That copy won't help you tell them apart. The seven questions below can, and you can answer each one on a tool's own site before you enter a single figure.
1. How does it simulate the future?
“Runs Monte Carlo simulations” appears on nearly every retirement tool, and it can mean two different things.
Some tools take the average historical return and how much it swings from year to year, build a smooth statistical curve from them, and generate random years from that curve. Others give each simulated year the returns of a real year of market history, so the bad stretches that happened come through as they were rather than as a smoothed average. Neither approach is wrong. The first can understate how bad a run of bad years gets. The second is only as good as the history it uses. Ask which one you're looking at, and how many years of history it uses. MangoDime draws from U.S. market years back to 1928.
2. What does it model, and what does it say it doesn't?
Any serious plan touches Social Security timing, taxes (including required distributions and Medicare surcharges), healthcare before 65, a home or a mortgage, and, for a couple, two separate timelines. Nearly every tool says it handles all of this.
The more useful question is whether the tool tells you where its modeling stops. A tool that publishes a plain list of what it doesn't cover has thought about it. One that doesn't may not have, or would rather you found out after subscribing. Ours is here, with a date on it.
3. Does it need your bank login?
Some tools require you to connect your accounts before they'll show anything, others offer it as an option, and a few never ask.
Linking works through an aggregator that holds a read-only connection to your bank, rather than your password. It's widely used and it saves you from updating balances by hand. It is also a third party holding a connection to your accounts, and that's worth choosing on purpose. A tool that never asks removes the decision. The cost is that you update your own numbers when they change.
4. What is free, and what needs a subscription?
“Free” means different things at different tools. One tool lets you build a complete plan at no cost and charges only for the analysis on top. Another is free because it makes money by referring you to a paid service once your numbers look large enough. Others have no free tier beyond a teaser.
Ask one concrete question: what can I see today, for nothing, with no card on file?
5. Can you see a number before you create an account?
It's the quickest way to narrow the list. Many tools require an account before showing any result, or show a sample person's numbers and keep yours behind signup. A few show you a result from nothing but your own inputs.
If you want to judge a tool's method before handing over an email address, this tells you in a minute whether you can.
6. What happens to your data?
With no account, does the tool store anything? With one, what exactly: your email, the figures you enter, a history of past inputs? Can you delete it, and does deleting mean deleting?
A privacy page that answers those questions in plain sentences is worth more than one that doesn't mention them.
7. Does it tell you what to do, or show you what your choices produce?
Of the seven, this one matters most. Planning software can rank options and show what each produces for your numbers. It can't know your whole situation, and without a license it shouldn't be telling you which option to take.
Words like shows, ranks, compares, and estimates are a good sign. Should, we recommend, and the right move is deserve a second look when they come from software rather than a person who is accountable for the answer.
Where MangoDime lands
There's no single right answer to these questions. Tools trade depth, cost, and convenience differently. Our own answers: we build simulations from market history back to 1928, and we publish a dated list of what we don't model. We don't offer bank linking, and if we add it, it will be optional. You see a number before making any account, we store nothing until you choose to save, and we rank options rather than give advice. If you'd like a first number to carry with you while you compare, the estimator below gives you one without a signup.
In today's dollars
The retirement figure lasts to 95 in 90% of simulations. Your $4,000 a month of spending is covered in 89% of them.
Add accounts, Social Security, and your partner/spouse. You still don't need to sign up.
Questions people ask
Should I use more than one tool?
It's a good check. Run the same inputs through two of them. If their results land close together, that's a good sign. If they don't, the gap usually comes from one of the questions above, most often the simulation method or the depth of the tax model.
Is a free tool as good as a paid one?
It depends on what you need. A free tool that's clear about its limits can be more useful than a paid one that isn't. Price tends to follow depth and support more than accuracy.
What if a tool won't say what it doesn't model?
Weigh that when you compare it with tools that do say.
How much do I need to retire?
There's no single figure. It depends on what you spend each month, not on your net worth. How much do you need to retire walks through why.
Planning software, not investment, tax, or legal advice.
MangoDime · Last updated October 5, 2026
MangoDime is built and written by Northstar Digital LLC, Laguna Beach, California.