Set six numbers, add the car, the child and the year off, and watch your net worth and monthly income run to age 80 across 400 simulated markets. No account, eight currencies.
Last updated: September 2026
The top chart is what you're worth at each age; the lower one is the monthly income that money could pay you then. Both come from the same run, so a pin you drag on one redraws the other.
The line is your net worth in today's money, so the figure at 70 is what it would buy this week. Watch where it bends: it climbs slowly from 30 to 36, while a partner is at home and only $200 a month goes in, then steepens when the full $700 resumes; it steps down at 40, 50 and 65 as each car is bought; the year off at 45 barely bends it — by then the pot's own growth dwarfs a year of contributions. After retirement at 55 it does not turn over — at the rates the page opens with, a 4% draw is smaller than the growth those assumptions imply, so the median runs $822,000 at 55, $1.30M at 65 and $4.08M at 80. The First $1M marker lands just before 60.
The lower chart asks a different question: at this age, what could the plan pay me per month? Read it where it changes shape — 55, when the salary stops and the withdrawal takes over; 64, when the partner's state pension starts; 67, when yours does. A pension is drawn as a step, not a ramp: it arrives in one month and stays.
A plan can end rich and still break in one year. Net worth is a stock; income is a flow. The line above can finish comfortably while one year in the middle is thin, and only the lower chart names that year.
The chance of success is a survival count: the tool runs 400 simulated futures on your assumptions and counts how many still had money at 80.
A chance of success is the share of 400 simulated futures in which the plan never ran out, given the growth, inflation, volatility and withdrawal rate you set.
It's a count, not a grade
The default plan here reads 93%: 373 of its 400 futures ended with money at 80, under assumptions you can change in ten seconds. It isn't a mark out of a hundred.
Two plans at the same number can be very different
One runs a small shortfall at 78 that a quieter year absorbs. The other runs dry at 65 with fifteen years still to fund. The percentage can't tell those apart; the charts can.
It moves on inputs you guessed
Move growth from 11% to 7% in the assumptions row and this plan's reading falls from 93% to 56%. If four points of a return nobody knows can decide the verdict, the verdict was never that precise.
Nobody lives pass/fail
A real plan gets adjusted. In Derek Tharp's worked case, a couple with $1M and $3,500 a month of Social Security starts at $6,769 a month at a 95% target and $8,462 at 50% — and median lifetime spending across the two rarely differs by more than $1,000 in real terms.
A 50% probability of success is really nothing more than a 50% probability that there will be something to do — i.e., to make some adjustment.
Two kinds of event live on this page and they behave differently: a one-off moves the line down once, a phase moves every month it covers.
The car at 40 is a one-off: $28,000 leaves the pot, the line steps down, and everything after it grows from a lower base. There are three of them — 40, 50 and 65 — because a car every ten years is the kind of cost a single retirement number never shows. The child from 30 is a phase: $500 a month less invested for six years while a partner is at home, the same reduction 72 times over. The two state pensions run the other way and never stop, $1,000 a month from 64 and $1,500 from 67. Drag any pin along the axis and the whole curve after it is redrawn.
The salary you skip is identical; the compounding is not. At 11% growth and 2.5% inflation — about 8.3% real, and a long-run average rather than a promise — money invested at 28 has 27 more years to work than money invested at 55, a factor of about 8.6 (1.083^27). The same missed year costs roughly eight and a half times as much taken at 28. Alex's own break shows the mechanism running forward: one year without investing at 45 skips $8,400 of contributions and costs about $18,000 by 55 and $132,000 by 80. The same missing year, growing with the pot.
Alex is the story the page opens on: 28, $45,000 of net worth, $2,800 a month of spending, $700 a month going in, retirement at 55 and a plan that runs to 80 — plus a first child from 30 (six years with $500 a month less invested, a partner at home), cars at 40, 50 and 65, a year off work at 45, a partner's state pension from 64 and Alex's own from 67. The figures below were computed in September 2026 from those defaults, and the tool above re-runs them the day you open it, so yours may differ by a rounding step. It opens in dollars; switch the currency and the whole story rescales.
Delete the career break and change nothing else: the plan holds $840,000 at 55, turns work-optional right on the retirement pin, and 94.0% of its 400 futures still have money at 80.
Put the year back — one year at 45 with nothing invested — and the same plan holds $822,000 at 55, work-optional lands a few months after the retirement pin, and the chance of success reads 93.3%. The year off costs about $18,000 by 55 and seven tenths of a point of chance. Ten years from retirement it is nearly free; the same year taken at 28 is not.
Now the part that looks wrong and isn't. Alex stops working at 55 and the net-worth line doesn't turn over: $822,000 at 55, $1.30M at 65, $4.08M at 80. At 11% growth against 2.5% inflation the plan assumes about 8.3% a year in today's money and draws 4%, so the pot keeps growing through a retirement that lasts twenty-five years — the first million lands just before 60, nearly five years after the salary stopped. Read plainly: that shape is the growth assumption, not a fact about retiring early. It sits on the page as a slider for exactly that reason.
So test the assumption the shape rests on. Set growth to 7% and change nothing else: the chance of success falls from 93.3% to 56%, the median at 80 falls from $4.08M to $139,000, work-optional slips from just after 55 to nearly 75, and the first million never arrives at all. A cheaper test: delete the partner's state pension and the chance falls about five points, to 88%. The gap between two versions of one life is what this tool is for.
Signing up costs an email and ten minutes of setup. In return these two charts run on the accounts, property and pensions you actually hold, instead of six numbers you typed under the charts.
The tool simulates your plan month by month to age 80, then runs it 400 more times with the returns varied, and reports what those 400 futures did.
Four numbers are yours to set, and the page starts at 11% growth, 2.5% inflation, 17% volatility and a 4% withdrawal rate — the app's own defaults; the (i) beside each slider says where the number comes from. Every figure is in today's money. The 400 runs draw monthly returns from a lognormal distribution around your growth figure at your volatility; in retirement the plan takes a fixed percentage of whatever the pot is worth that year, which is why the income line falls when markets do. The shaded band is the p25–p75 range: half the runs landed inside it.
Tax is the big absence — no income tax, no capital gains, no account wrappers — and it works against these figures, not for them. Healthcare isn't modelled. Nor is a property with a mortgage against it, where the loan magnifies the gain and the loss alike. Nor is the order in which you'd draw accounts down, which is where much of real retirement planning lives. No state pension is assumed: the default story types two in by hand, a partner's at 64 and Alex's own at 67.
The assumptions behind every free tool on this site are written up on the methodology page, including where the figures come from and when they were last checked.
The score puts your net worth against the wealth distribution for your age band in your country — the same datasets behind the site's net-worth percentile tool. It's a position, not a verdict: where you stand among people your age who live where you live.
There are six levels, from Building momentum to Top 1%, and under each one the card prints the year this plan is projected to cross it, so a level you haven't reached comes with a date rather than a lecture. Datasets exist for the United States, the United Kingdom, Canada, Czechia, Germany (used for the euro) and Poland. In Switzerland or Australia, pick the closest country in the card and read the placement as rough.
Under the charts, in “Start with six numbers”, set: currency, age, net worth today, monthly spending, monthly investing, and the age you want to stop working.
Read the top chart for the shape of your net worth and the lower one for the monthly income behind it.
Make the story yours. Open the events rail and edit the cars, the child, the career break and the two pensions — or delete the ones that aren't your life.
Open the Assumptions row in that same card and set growth, inflation, volatility and the withdrawal rate to figures you'd defend to a sceptic.
Read the chance of success, change one thing — retire two years later, cut a phase — and read it again. The difference between two runs is the part worth acting on.
Every price and tier below comes from the tool's own pricing page. Two of them are good products that charge for what this page does for nothing.
| Tool | Cash flow | What-if scenarios | Chance of success | Currencies | Account needed | Price |
|---|---|---|---|---|---|---|
| This page | Yes | Yes | Yes, 400 paths | 8 | No | Free |
| ProjectionLab | Premium, $129/yr | Premium, $129/yr | Free tier | USD; other currencies in Premium | Sandbox needs none; free tier needs signup | $0 · Premium $129/yr |
| Boldin | Yes | Yes | PlannerPlus, $144/yr | US only | Yes | $0 · PlannerPlus $144/yr |
| FIRECalc, cFIREsim, FI Calc | No | Limited | Historical cycles | US data only | No | Free |
| The big free US dashboard | Yes | Partial | Yes | US only | Account + bank login | Free; funded by advisory services |
Checked September 2026. Tiers and prices change — check theirs before you decide.
ProjectionLab's pricing page puts Cash-Flow Projections, What-If Scenarios and International Planning in Premium at $129 a year; Boldin's puts Monte Carlo in PlannerPlus at $144 a year, as published in September 2026. Both are good tools, worth the money to the people who need what they do. The big free US dashboard really is free: it wants your bank logins, and the advisory follow-up is what its users report across reviews rather than something the company documents.
It's free and there's no account. Set the six numbers under the charts and everything redraws when you leave each field — no email, no card, no bank connection. The paid app behind it is the part that saves a plan and keeps it current against your real balances.
It's the share of 400 simulated futures in which the money never ran out, given the assumptions you set — a survival count, not a grade. Two plans can read the same number while one risks a small shortfall at 78 and the other runs dry at 65.
There's no threshold that's right for everyone, and a lower number is more survivable than it sounds if you're willing to change something later. Kitces' Derek Tharp argues a 50% probability of success is really a 50% probability that there will be something to adjust. Under 70%, read it as a prompt to find the thin years.
The FIRE planner answers one question — when does the money cover the spending — and holds the rest still. This page lets the middle be messy: a child from 30, cars at 40, 50 and 65, a year off at 45. For the date alone, the FIRE planner is faster.
Yes, and there's one in the default plan at 45. Move it to the age you're actually thinking about, set how long it lasts, and both charts redraw. Alex's year off skips $8,400 of investing and leaves the plan about $18,000 smaller at 55 — cheap ten years from retirement, and far dearer if you move it to 28.
Yes. There's no Social Security, 401(k), Medicare or IRMAA in the model, and it runs in eight currencies: USD, EUR, GBP, CZK, PLN, CAD, CHF and AUD. It won't work out your state pension, though — add it as an income stream with the age it starts, the way the default story does twice, at 64 and 67.
Net worth is a stock: what you're worth at that age. Income is a flow: what the plan could pay you per month at that age. A plan can end rich and still contain a year you'd feel, and that year shows up on the second chart while the first glides over it.
Growth, inflation, volatility and the withdrawal rate are the four you set; the page starts at 11%, 2.5%, 17% and 4% — the app's own defaults, each with an (i) beside its slider — and shows everything in today's money. It doesn't model tax, healthcare, a property with a mortgage against it, or the order your accounts get drawn down.
No, and be wary of anything that says it can. It projects one scenario and puts a range around it. The value is the comparison: run it with the sabbatical and without, and the gap between the two curves is a real number you can decide against.
The numbers stay in this browser tab: reload and they're still there, come back tomorrow and you'll meet Alex again, because nothing carries between visits. The page fetches exchange rates and the country wealth statistics behind the health score, and records anonymous usage analytics like the rest of the site. There's no account here, so nothing you type is attached to a person.
This page owns the middle of your life. The others answer narrower questions faster.
I built this because I was doing it in a spreadsheet, and the spreadsheet couldn't tell me what a year off would cost. This page won't remember you — that's the price of not asking for your email. The app behind it does: your real balances feed the same plan, property, mortgages, pensions and insurance join it, and it re-runs on today's numbers every time you open it.
See what it costsThis page is a model, not advice. Every figure depends on assumptions you chose, and real markets don't deliver an average year on schedule. Nothing here accounts for your tax position or your country's pension rules. Use it to compare two versions of your own plan, and talk to a licensed adviser before a decision that's hard to reverse.
The same two charts, fed by the accounts, property and pensions you actually have, re-run on today's balances every time you open them.
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