What is WalletBurst?
WalletBurst is a personal finance site that publishes free, interactive calculators. Its FIRE section has a Coast FIRE calculator, a FIRE calculator, a Fat FIRE calculator and a Barista FIRE calculator, plus a crowdsourced Coast FIRE jobs database and two calculators that show how a windfall or a one-time purchase moves your FIRE date[1]. Beyond FIRE it covers real estate, loans, compound interest, savings rate and vehicle running costs. It also sells a Wealth Planning Toolkit for Google Sheets for $20, which includes a net worth tracker and more advanced FIRE and Coast FIRE spreadsheets[1].
Its calculators are built for speed. You type a few numbers, move sliders for growth, inflation and withdrawal rate, and a chart redraws as you go. Each one sits on a page that explains its formula in plain language, which makes WalletBurst a clear place to learn what a Coast FIRE number is.
FIRE Calculator Pro covers the same ground with a different emphasis. Each FIRE calculator here runs the deterministic projection you would expect, then runs the plan again through a 2,000-run Monte Carlo simulation and a replay of every historical retirement in 1928-2025 data[7]. That second step is the main difference, and the rest of this page shows what it changes.
How do WalletBurst and FIRE Calculator Pro compare?
This table covers the FIRE calculators only. Each WalletBurst entry links to the page where we confirmed it.
| Feature | WalletBurst | FIRE Calculator Pro |
|---|---|---|
| FIRE calculators | Coast, FIRE, Fat and Barista FIRE, plus windfall and purchase timeline tools[1] | FIRE, Coast, Barista, Lean, Fat, FIRE number, early retirement, savings longevity and more |
| Returns | One growth rate; the FIRE and Fat FIRE tools blend stock, bond, cash and other returns by allocation[3] | One expected return for the projection, plus a stock and bond mix for the risk tests |
| Inflation | Subtracted from the growth rate[2] | Fisher equation, after fees |
| Investment fees | Not among the Coast FIRE inputs[2] | Separate input (default 0.1%) |
| Social Security or pension | Not among the Coast or Barista FIRE inputs[2][4] | Optional inputs with their own start ages |
| Salary, 401(k) match, income growth | Yes, in the FIRE and Fat FIRE calculators[3] | Take-home pay and spending; no employer match field |
| Monte Carlo and historical tests | Not described on the calculator pages; they use the compound interest formula[2][3] | 2,000-run Monte Carlo and every historical start year since 1928 |
| Ads | Privacy policy says it works with Mediavine on interest-based advertising[6] | No ads; Google Analytics counts visits but never receives your inputs |
| Extras | Coast FIRE jobs database; $20 Google Sheets toolkit[1] | Share links, CSV export, UK, Canada and Australia editions of the FIRE and Coast FIRE calculators |
WalletBurst details checked on its own pages in November 2026. FIRE Calculator Pro details are from our methodology page.
How does each tool calculate your Coast FIRE number?
Both tools start from the same idea. Your FIRE number is your annual retirement spending divided by your safe withdrawal rate. Your Coast FIRE number is the amount that, left alone to compound, grows into that FIRE number by your retirement age. WalletBurst writes it as spending divided by the withdrawal rate times (1 + n)t, where n is the growth rate and t is the number of years[2].
The differences are in the details around that formula:
- Inflation. WalletBurst subtracts the inflation rate from the growth rate to get a real return[2], so 7% growth and 3% inflation become 4%. We use the Fisher equation, (1 + return − fees) ÷ (1 + inflation) − 1, which gives 3.88% with no fees and 3.79% after our default 0.1% fee. Over 37 years of compounding, that small gap matters.
- Income in retirement. We value each retirement year's spending after Social Security, pensions or part-time pay, so income that starts at 67 lowers the target from that age on. With flat spending and no other income, our target is exactly spending divided by the withdrawal rate, the same as WalletBurst's.
- Contributions. Both tools draw your path with ongoing contributions. On WalletBurst the chart shows net worth with continued contributions and with none after the Coast FIRE milestone[2].
Worked example: WalletBurst's defaults in our engine
WalletBurst's Coast FIRE calculator opens with a 30-year-old who plans to retire at 67 on $30,000 a year, with 7% growth, 3% inflation and a 4% withdrawal rate. For those inputs it shows a Coast FIRE number of $175,723[2]. Here is the same plan in our engine, one change at a time.
| Method | Real return | Coast FIRE number at 30 |
|---|---|---|
| WalletBurst, as displayed[2] | 4% | $175,723 |
| Our engine, Fisher, no fees | 3.88% | $183,163 |
| Our engine, Fisher, 0.1% fees | 3.79% | $189,611 |
| Plus $12,000/yr Social Security from 67 | 3.79% | $113,767 |
| Plus $24,000/yr Social Security from 67 | 3.79% | $37,922 |
Our rows: calculated with the FIRE Calculator Pro engine. The $30,000 target at a 4% withdrawal rate is $750,000 at 67. All figures in today's dollars.
The return method and the fee move the number by about 8%. Social Security moves it much more. With $12,000 a year starting at 67, the portfolio only has to cover $18,000 a year, so the target at 67 drops to $450,000 and the coast number falls to $113,767. If your benefit will cover most of your spending, leaving it out can make Coast FIRE look many years further away than it is.
What happens if markets don't deliver the average?
A Coast FIRE number is a break-even point. Hit it exactly, earn exactly the assumed return every year, and you arrive at retirement with exactly your FIRE number. Real returns arrive in an uneven order, and the years around your retirement date matter most[8]. So we asked a simple question of the plan above: if this 30-year-old invests the coast number, never adds another dollar, and spends $30,000 a year from 67 to 95, how often does the money last?
| Invested at 30, then no contributions | Raw history | Matched to 3.79% real | 10th percentile at 67 |
|---|---|---|---|
| $175,723 (WalletBurst default) | 89% | 59% | $211,741 |
| $189,611 (our coast number) | 90% | 62% | $228,475 |
Our calculation: 2,000 Monte Carlo runs, seed 2026, 80% stocks and 20% bonds, 0.1% fees, US data 1928-2025[7]. The last column uses the matched model.
Two things stand out. First, at our 3.79% real return, $175,723 grows to $695,067 by 67, short of the $750,000 target, because of the return method and the fee. Second, even our own coast number is only a midpoint. When history is shifted so its average matches the return you entered (“Match my return”), coasting from exactly that number lasts to 95 in 62% of runs, and in the weakest tenth of runs the balance at 67 is $228,475 or less. Replaying history as it happened gives higher success, because the past century's returns were higher than 3.79% after inflation.
None of this is a flaw in WalletBurst's arithmetic. It is the limit of any single-return projection, ours included. The practical lesson is to keep contributing for a while after you first cross the line, or to plan on part-time income if markets disappoint. Our Coast FIRE calculator shows these odds for your own inputs and has a slider for what happens if returns disappoint after you stop contributing.
How do the Barista and Fat FIRE calculators differ?
WalletBurst's Barista FIRE calculator asks for your take-home pay, current expenses, invested net worth, the age you want to switch, your retirement spending and your monthly income during Barista FIRE. It then compares reaching full FIRE with and without the switch to part-time work[4]. Our Barista FIRE calculator asks when you go part-time, how much you earn, and when you stop part-time work entirely, and it can add Social Security or a pension. It then shows the portfolio you need on the day you go part-time and runs the same risk tests.
WalletBurst's FIRE and Fat FIRE calculators share one detailed input set: pre-tax and post-tax salary, current and retirement spending, net worth, an allocation across stocks, bonds, cash and other assets with a return for each, a 401(k) match and an income growth rate. A yearly finances table shows the year-by-year path[3][5]. That is more detail on the saving side than our calculators ask for. Our Fat FIRE calculator focuses on the spending side instead: spending tiers, tax on withdrawals and how a lower withdrawal rate changes the target.
How do you check a WalletBurst plan here?
If you already have a Coast FIRE number from WalletBurst, you can re-run it on our Coast FIRE calculator in a couple of minutes. Most inputs carry straight across:
- Ages, spending and savings. Current age, retirement age, annual spending in retirement and current invested assets map to the same fields. WalletBurst asks for a monthly contribution, and so do we.
- Growth and inflation. Enter the same nominal growth and inflation rates. We convert them with the Fisher equation, so expect a slightly lower real return than WalletBurst's subtraction gives.
- Fees. Set fees to 0% if you want to match WalletBurst's inputs, or enter your fund costs if you want them counted.
- Social Security. Add your estimated benefit and the age you plan to claim it. If you had lowered your spending on WalletBurst to allow for it, put your full spending back in.
- Plan-until age. We ask how long the money must last (95 by default). It does not change a flat-spending target, but it sets the length of the risk tests.
With fees at zero and no other income, the two tools should differ only by the return method, about 4% on WalletBurst's defaults. A bigger gap usually means an input was entered differently.
When should you use WalletBurst instead?
- You want a quick visual answer. The sliders and chart make it easy to see how growth, inflation and withdrawal rate move a Coast FIRE number.
- You model 401(k) matching and raises. Its FIRE and Fat FIRE calculators include an employer match and income growth[3].
- You want the extras. The Coast FIRE jobs database and the windfall and purchase calculators have no equivalent here[1].
- You prefer a spreadsheet. Its $20 Google Sheets toolkit lets you build on the model yourself[1].
When should you use FIRE Calculator Pro?
- Social Security or a pension is part of your plan. Income that starts later lowers your target only from the age it starts.
- You want to know how likely the plan is to work. Each FIRE calculator reports a Monte Carlo success rate and the result of every historical start year since 1928.
- You plan a long early retirement. Set any plan-until age and see how a 4% withdrawal rate holds up over 50 or 60 years, not just 30.
- You want a page with no ads. Calculations run in your browser and nothing you type is sent to us. See the privacy policy.
- You live in the UK, Canada or Australia. Our FIRE and Coast FIRE calculators have local editions in pounds, Canadian and Australian dollars, with local accounts and government pensions.
Many people use both: WalletBurst to explore the idea, then a risk-tested plan to decide how much margin to keep. Every formula we use is on the methodology page.