Frequently asked questions

No. Your numbers are never fed into AI models.

• Nothing goes to AI companies. The income, debts, balances and plans you enter stay in your account. This site never sends them to any AI service, so they can’t end up in anyone’s training data.
• How I use AI. I use Claude, an AI assistant made by Anthropic, to help me write and test the code behind this site, using made-up test data. I also use it to look into error reports, which are stripped of anything you typed before they ever reach me.
• No access to your information. I never give an AI tool access to your account or your figures. It works on the code, not on your data.

Yes, absolutely. So when you use this site, the number of AI requests it makes is zero. Not fewer. None.

• AI tools answer live (probabilistic). Each question or click is sent to a large AI model running on specialized hardware in a data center, which works out a fresh answer every time. That’s where AI’s energy and cooling costs come from.
• This site follows exact formulas (deterministic). The same inputs always give the same answer, like a calculator or a spreadsheet. Your whole projection, every month out to age 90, takes an ordinary server well under a second. When I timed it on a test server, it took about a twentieth of a second.

In plain terms: every time you use this site, it uses far less electricity than an AI-powered tool doing the same job, because the heavy part (running an AI model) never happens.

I do use Claude while I’m building the site, to help write and test the code, and that takes energy; I won’t pretend otherwise. But that happens once, while the code is written, not every time someone runs a projection.

No. Like many of you, I don't particularly care to have corporations constantly trying to mine my data for their own profit. And because I don't like when it's done to me, I don't do it to you.

I don't sell your data, and I don't show ads. Your information goes only to the services needed to run the site, and only what each one needs: the hosting provider (stores your account and projections on US servers), Stripe (processes payments; you enter your card directly with Stripe, so it never touches this site's servers), an email delivery service (sends your account emails), and a network security service (protects the site and secures the connection). Beyond that, information is disclosed only if the law requires it, or if the business were ever sold, as described in the Privacy Policy, section 4.

Only what the business genuinely needs. Your card number and security code go straight to Stripe, the payment processor, and never reach this site. Stripe sends me a record of each payment, and from it I keep:

• Stripe’s reference numbers for the payment, your subscription and your customer record: to give refunds, handle renewals and cancellations, and open Stripe’s page where you update your card.
• Your account number, the plan you chose, and the consent boxes you ticked: to switch on the right access, and to show what you agreed to if it’s ever in question.
• The affiliate code, if you came through someone’s link: to pay that person their commission, or take it back if you refund.
• The amounts and dates: what you paid, any discount, any refund, and when: for refunds, commissions and tax records.
• The payment’s status (paid, refunded, a renewal retry, a dispute): to keep your access correct and sort out problems.
• The country your card was issued in: because the service is for US residents only.

What I don’t keep from the payment: your name, email, billing address, phone number or card details. Stripe holds those so it can charge your card, and you manage them with Stripe directly. Every email I send goes to the address on your account, the one you gave at sign-up. And you can wipe every financial figure you’ve entered at any time with “Reset my data” in your settings, after one confirmation step.

No. Every number is an educated estimate, not a guarantee, and not financial, tax or legal advice. You can see every month’s figures, and a loan’s payments and balance can be checked against your own statement, but nobody can promise what markets, prices or the law will do.

It can be. Once you’re retired, the question changes from “will I have enough?” to “will what I have last?”, and that’s the question the projection answers. It runs month by month to age 90, or for at least 10 years if you’re already close to or past that age.

It is only as good as the numbers you give it, so it works best with your real balances, income and spending. It doesn’t pick investments and it isn’t financial, tax or legal advice. If you try it and it isn’t for you, see What if it’s not for me?

The younger of you. The projection runs until the younger partner reaches 90, because the household’s money has to last as long as either of you might need it.

Even that isn’t perfect, and no formula can make it perfect. Nobody can know which of you will die first, and it could be the younger one. So I plan for what can reasonably be foreseen, point out the blind spots I can see, and make it quick to update your plan when life changes. No projection can ever be 100% right: treat it as a map you redraw as you go, not a promise.

For 30 days after any purchase, including a renewal, you can refund it yourself from your account in two clicks, with no explanation needed. The full details are in the Refund Policy.

I plan to age 90 rather than to average life expectancy. Life expectancy is a median: half of people live longer than it, so a plan built around it would mean roughly half of plans quietly running out. Planning to 90 leaves a deliberate buffer, because outliving your money is the risk worth guarding against. If your money lasts to 90, you are in good shape.

You don't set them. I publish them. Your dashboard shows every economy-wide assumption (market return, inflation, savings return and the tax rate used in retirement) with its source and a link to it. They are set centrally rather than per person, because a number someone nudged up and forgot about is the fastest way to a projection that flatters instead of informs.

Your real benefit depends on your full earnings history and on future law, and neither is something this tool can see. Unless you enter your own figure, it estimates one from your pay. For an accurate number, sign in to your my Social Security account at ssa.gov and enter the estimate it gives you.

Because that's how your real money moves. Loans are paid monthly and interest compounds monthly, so the tool works out every single month of your projection. That means you can hold a loan’s payments and balance up against your own statement and see them match. Further out, savings and investments are estimates built on the assumptions shown on your dashboard.

Because I don’t zoom in. People judge a chart with their eyes before they read the small numbers down the side, and a chart that doesn’t start at zero can make a small change look like a cliff. I consider that a psychological trick, so every chart here follows two rules:

1. Every chart starts at $0. The height you see is the real size of the money. The one exception: if a figure itself falls below zero, the chart reaches down to show it rather than hide it.
2. Before-and-after charts share the same scale. In the Strategy Sandbox, your plan now and your experiment use the same top value, so a modest improvement looks modest and a big one looks big.

That way your eyes get the same honest picture as the numbers.

Because the two buttons measure your money with different rulers.

• Today’s $ (i.e., real dollars) shows what your future money will buy, priced as if everything still cost what it costs now.
• Tomorrow’s $ (i.e., nominal dollars) shows the actual number of dollars you’ll have in that year: the figure you’d see on a statement at the time.

Switching between them isn’t one flat adjustment, because prices rise on top of last year’s prices. Say prices go up about 3% a year: something that costs $100 today costs about $103 next year, about $181 in 20 years and about $243 in 30 years. So a point 30 years out gets stretched far more than a point next year, and the line bends instead of just getting taller.

That’s also why savings that slowly shrink in Today’s $ can look flat, or even look like they’re growing, in Tomorrow’s $. The number of dollars goes up while what those dollars can buy goes down. I show Today’s $ first because it’s the one to plan with; Tomorrow’s $ is there if you want to compare against a future statement.

On purpose. Money talk is full of jargon, and jargon is one of the biggest reasons people avoid looking at their numbers at all. I want everyone to be able to read every screen, so buttons and labels use everyday words. Where the technical term helps, I add it in brackets, like “Tomorrow’s $ (i.e., nominal dollars),” so if you already know the lingo, you know exactly what you’re looking at.

Nothing is wrong, and it isn’t this tool: it is how every standard mortgage works. Your payment stays the same each month, but the interest is charged on whatever you still owe. Early on you owe the most, so most of the payment goes to interest and only a little reaches the balance. As the balance comes down, the interest shrinks and more of the same payment goes to paying the loan off.

An example: a $450,000 loan at 7% over 30 years has a payment of about $2,994. In the first month, $2,625 of that is interest and only $369 comes off the balance. After a full year of payments (about $35,900 paid) the balance is down by about $4,600. It takes roughly 20 years before more of each payment goes to the loan than to interest. In the final year almost all of it does.

If your payment includes property tax and homeowners insurance (escrow), that part never touches the balance at all. The month-by-month view on your dashboard shows your own mortgage balance at the start and end of every month, so you can watch this happen with your numbers.

Each loan is compared only with the average for its own kind of loan, from the Federal Reserve’s survey of US banks (the G.19 release, August 2026 survey):

• US bank credit cards that charge interest: 22.36%
• 60-month new-car loans at US banks: 7.54%
• 24-month personal loans at US banks: 11.90%

A note appears under a loan only when both of these are true:

• its rate is at least 1 percentage point above that average, and
• at today’s balance, the difference costs at least $100 a year in extra interest.

Why both? Lenders price by credit score, so averages hide a wide spread, and being a little above average is normal rather than a sign of a bad deal. And a big gap on a small balance can cost less in a year than a lunch out. If your rate is at or below the average, or the difference is small, you see nothing, because there’s nothing worth your attention. An average is not an offer: what you’d be offered depends on your credit.

Some loans are never compared: used-car loans (see the next question), federal student loans (their rates are set by law), loans you haven’t taken out yet, and anything without a published average, such as medical debt or a mortgage. The averages are updated every quarter; if one gets too old, the comparison hides itself rather than show a stale figure.

Because only one of them has a published average to compare with. The Federal Reserve’s survey reports rates for new-car loans, and none for used-car loans, which lenders price differently. Comparing a used-car loan with the new-car average could tell you you’re overpaying when you’re not, so a new-car loan is compared with the new-car average and a used-car loan isn’t compared at all. Everything else works the same for both. A loan saved before the two types existed shows “Auto loan (new or used?)” until you pick one.