Why I Built Evernest — From Spreadsheets to a Retirement Calculator

The short version

I'm a recently retired software engineer. I manage my own money. A few years ago I started trying to figure out when I could retire, and I couldn't find a calculator online that was actually useful. So I spent a few years gradually building out my own series of spreadsheets. Friends and family tried it, they liked it. Then I converted it to an application and put it online. That's Evernest.

Here's the longer version.

Every calculator I tried was too isolated from real world dynamics

I'm a pretty self-directed person. I do my own taxes, manage my own investments, so when I started thinking seriously about retirement, I did what anyone would do — I Googled "retirement calculator."

I couldn't find one that was exactly what I was thinking. There are a few pretty decent ones, that allowed me to enter "other", such as a future home sale. But the ease of use was not there, they were hard to save and resume, and it was hard to make a quick change and see how that impacted the entire picture.

Most of them are click-bait. You type in a few numbers, hit calculate, and you get back something like "You need $1.2 million." But my actual question wasn't ONLY "how much do I need." My questions were also "When should I take Social Security?", "When should we downsize?", "When should my spouse take Social Security?". And those questions don't have a simple answer, because when you change one factor, the answers can change. If you sell your house right away perhaps you can delay taking SS, etc.

If I claim Social Security at 62, I get a smaller check but I stop drawing from my portfolio sooner. If I wait until 70, I get a bigger check but I'm burning through savings for 8 extra years. Which one is better? It depends. Are we still helping our kids? Are we downsizing? Am I doing any consulting work? Is my spouse still working? Every one of those things changes the answer.

None of the online calculators could handle that.

The "serious" tools weren't much better

So then I looked at the paid tools. Some of them were actually pretty powerful, but they had their own problems. They wanted to link to all my accounts. They cost $150-$1,200 a year. They were packed with features I didn't need — Roth conversion optimizers, tax-lot harvesting, estate planning stuff. I didn't want any of that. I just wanted to see my cash flow over time and be able to change things and see what happens.

And honestly, a lot of them felt like glorified lead-gen for financial advisors. Sign up for the "free" tool, and pretty soon someone's trying to manage your portfolio for 1% a year.

All I wanted was: if I spend this much, earn roughly this much, and make these specific life changes at these specific ages... does my money last? That's it. Nobody was answering that question well.

The spreadsheet era

So I opened Excel and started building.

Over a couple years I ended up with this series of increasingly ridiculous spreadsheets. They modeled my cash flow year by year. I could plug in Social Security at different ages, add a home sale, add consulting income, change my spending — and everything would recalculate. It wasn't pretty. Some of the formulas were pretty impressive!

"You should put that online"

I ended up using the spreadsheets for a few friends and relatives. "You should put this online," they kept saying.

That project became Evernest.

What it does (and what it doesn't)

Evernest does exactly what my spreadsheets did, except it doesn't look like a crime scene. Year-by-year cash flow projections. Social Security at any claiming age. Financial events at any age — sell your house, start consulting, stop helping the kids, whatever. Change anything and the whole projection updates instantly. And now it has Monte Carlo stress-testing too, which my spreadsheets definitely never had.

What it doesn't do: it's not a financial advisor. It doesn't pick stocks. It doesn't optimize your tax strategy. It doesn't link to your brokerage accounts. If you need that stuff, go talk to a professional — seriously.

But if you're the kind of person who just wants to sit down, put in your own numbers, and figure out whether your plan actually works? That's what this is for. I built it because I needed it, and it turns out a lot of other people do too.