# The Best Coast FIRE Calculators (September 2026), Compared Honestly

> We checked 8 Coast FIRE calculators, including WalletBurst, NerdWallet and Clark.com: what each one models, where they differ, and who each suits.

Source: https://mycoastfire.com/blog/best-coast-fire-calculators
Last updated: 2026-09-14

For a quick number, NerdWallet or firenum.com is fine. If you want monthly contributions and inflation in the math, use WalletBurst, coastfirecalculator.app or ours. If Social Security is a big part of your plan, Pelcro and Clark.com build it in.

I loaded each of these calculators in September 2026, ran their default numbers and wrote down every input they ask for. Where I couldn’t see a feature on the live page, the table says “Not shown” rather than guessing. One disclosure up front: MyCoastFIRE is our site. It’s on the list because it’s a real option, and I’ve tried to be as plain about its gaps as about anyone else’s.

## Quick picks

-   Fastest single number: [NerdWallet](https://www.nerdwallet.com/investing/calculators/coast-fire-calculator). Five fields, one answer.
-   A quick number in another currency: [firenum.com](https://firenum.com/coast-fire), which offers nine.
-   Contributions, inflation and a chart: [WalletBurst](https://walletburst.com/tools/coast-fire-calc/), [coastfirecalculator.app](https://coastfirecalculator.app/) or [MyCoastFIRE](https://mycoastfire.com/).
-   Social Security built into one calculator: [Pelcro’s US calculator](https://www.get.pelcro.com/tools/coast-fire-calculator/us).
-   The most levers, from raises to inheritances: [Clark.com](https://clark.com/coast-fire-calculator/).
-   Taxes, account types and a whole-life plan: ProjectionLab, which is a different kind of tool.

## What should a Coast FIRE calculator get right?

Four things matter more than how the page looks.

The first is how it handles returns. Your [Coast FIRE number](https://mycoastfire.com/coast-fire-number) is your FIRE number shrunk back to today by expected growth. If your spending is in today’s dollars, the growth rate has to be in today’s dollars too. That means the real return, not the nominal one.

Here’s how much that matters. Say you’re 30, you expect to spend $60,000 a year and you want to retire at 65. At a 4% withdrawal rate your FIRE number is $1,500,000. With a 7% return and 3% inflation, your real return is 3.88% and your Coast FIRE number is $395,332. Type 7% into a formula that expects a real return and you get $140,494. That’s about a third of the honest figure. You could stop contributing thinking you’re done, with roughly $254,838 still missing, and not find out for a decade.

The shortcut of subtracting inflation from the return (7% minus 3% is 4%) gets you $380,123. That’s close enough to plan with. The exact version divides instead: (1 + 7%) / (1 + 3%), minus 1.

The second is contributions until you coast. The number tells you where the line is. What you add each month decides when you cross it. Same 30-year-old, $50,000 invested, adding $2,000 a month: that’s about age 50 in our model. A calculator with no contribution field can’t answer “when?” at all.

Third, you should be able to change the withdrawal rate. Dropping from 4% to 3.5% raises that $60,000 spender’s FIRE number to $1,714,286, and plenty of people retiring before 60 plan with something lower than 4%.

Last, the tool should show its formula and defaults so you can check the work. WalletBurst, firenum.com, coastfirecalculator.app, Pelcro and Clark.com all explain their method on the page. Ours is on the [methodology page](https://mycoastfire.com/methodology).

## How the calculators compare

Checked in September 2026. “No” means I saw the calculator’s full list of inputs and that field isn’t there. “Not shown” means I couldn’t confirm it either way.

| Tool | Contributions input | Inflation input | Social Security | Couples | Shareable link | Extras |
| --- | --- | --- | --- | --- | --- | --- |
| MyCoastFIRE (ours) | Yes, monthly | Yes | Separate calculator | Separate calculator | Yes, with your inputs | Coast FIRE age, progress, projection chart |
| WalletBurst | Yes, monthly | Yes, subtracted from return | No | No | Not shown | Chart with and without contributions after you coast |
| NerdWallet | No | No | No | No | Not shown | Progress toward Coast FIRE; 4% rate is fixed |
| firenum.com | No | No, return is treated as real | No | No | Yes, with your inputs | 9 currencies, by-age table |
| coastfirecalculator.app | Yes, monthly | Yes, with nominal return | Separate calculator | Separate calculator | Not shown | Pension version; Canada, UK and India versions |
| Pelcro (US) | Yes, monthly or yearly | Yes, with nominal return | Yes, amount and start age | Not shown | Yes, with your inputs | Year-by-year table, retirement income breakdown |
| Clark.com | Yes, plus yearly raises | Yes | Yes, amount and claiming age | Combine both partners’ amounts | Not shown | Other income, lump sum, life expectancy |
| M1 | Yes, monthly | No, return is treated as real | No | No | Result link, progress only by default | Future lump sum; monthly amount to coast in 5 or 10 years |

## Each calculator, in more detail

### MyCoastFIRE (ours)

You enter your current age, retirement age, yearly retirement spending, what you have invested and your monthly contribution. Expected return, inflation and withdrawal rate sit under an assumptions panel. It shows your Coast FIRE number, FIRE number, the age you cross the line at your contribution, how far along you are and a projection chart. The URL keeps your inputs, so you can send someone the exact scenario. It’s free, with no sign-up and no ads.

The limits are real. The main calculator works in US dollars, and the only other currencies are in our UK, Canada and Australia versions. It doesn’t model taxes or account types, so a dollar in a traditional 401(k) counts the same as a dollar in a Roth. It assumes one steady average return, and the moment you cross the line it stops your contributions entirely, with no option to keep saving half. There’s no year-by-year table either. For Social Security, couples and market randomness we have separate tools: the [calculator with Social Security](https://mycoastfire.com/coast-fire-calculator-with-social-security), the [couples calculator](https://mycoastfire.com/coast-fire-calculator-for-couples) and the [Monte Carlo version](https://mycoastfire.com/coast-fire-monte-carlo-calculator).

Try the 30-year-old from this post

Then change the return or inflation and see how far the number moves.

[Open the calculator with these numbers](https://mycoastfire.com/?assets=50000)

### WalletBurst

WalletBurst asks for age, retirement age, spending, invested assets and monthly contribution, with sliders for growth rate, inflation and safe withdrawal rate. Its chart is the best part: one line shows your net worth if you keep contributing and another shows what happens if you stop once you hit the milestone. It handles inflation by subtracting it from the return, so its Coast FIRE number comes out a little lower than the exact method gives. Best for visual people who want to play with sliders.

### NerdWallet

NerdWallet’s calculator asks for annual spending, target retirement age, current age, amount invested and expected return (6% by default). It shows your Coast FIRE number, retirement target, years to retirement and your progress, with the withdrawal rate fixed at 4%. The tooltip suggests a 5% to 7% return, and the page notes that the stock market’s roughly 10% average doesn’t account for inflation, so treat your entry as a real return. Best for a 20-second sanity check.

### firenum.com

firenum.com asks for current age, retirement age, monthly expenses, expected return and withdrawal rate. There’s no field for what you’ve already saved, so it tells you the target but not your progress. The page says it uses real returns and defaults to a cautious 5%. The share button copies a link with your inputs, and a currency switch covers USD, EUR, GBP, JPY, CAD, AUD, CHF, INR and NZD. Best if you’re planning outside the US or want a conservative default.

### coastfirecalculator.app

This one splits nominal return (7%) from inflation (3%) and shows the exact real-return formula on the page. It also has monthly contributions, a projection chart and separate calculators for couples, Social Security, pensions and Canada, the UK and India. The default monthly contribution is $0, so put yours in before reading the result. Best if you want the nominal and inflation split plus a variant for your situation.

### Pelcro

Pelcro’s US calculator puts Social Security in the main tool: you enter a monthly benefit and the age it starts, and it offsets your spending. It adds a toggle for whether you keep contributing after you coast, a monthly or yearly contribution switch, a year-by-year table and a breakdown of retirement income by source. The share button copies a link with your inputs, and there are versions for Canada, the UK, Spain, France and Egypt. Best for US readers who want Social Security in the same screen.

### Clark.com

Clark.com’s calculator has the most inputs of any here: life expectancy, a savings rate after you coast, yearly raises to your savings, Social Security with a claiming age, other income like pensions, a future lump sum and separate returns before and after retirement. It doesn’t use a withdrawal rate. It sizes your target to last until your life expectancy, with a balance you choose to have left over, so its number won’t match the 4% tools. Its default pre-retirement return is 9% before inflation, which I’d lower. For couples, the page tells you to combine both partners’ amounts. Best for people who want detail and will check each default.

### M1

M1’s calculator treats its 7% default as a real return and uses the 4% rule. Beyond the usual fields, it adds a future lump sum and shows how much more you’d need to add each month to coast within 5 or 10 years. Sharing creates a link that shows your progress as a percentage, with dollar amounts only if you choose. M1 is a brokerage, and the page asks you to open an account. Best if you like “how much per month to get there by X” framing.

## Do you need full planning software?

Probably not for Coast FIRE alone. But if your real question is about Roth conversions, account types, or you and a partner retiring at different ages, a calculator is the wrong tool. ProjectionLab’s homepage lists Monte Carlo simulations, tax analytics, Roth conversions and planning as a couple, with basic projections free and premium plans on top. Coast FIRE becomes one milestone inside a bigger plan.

If you’re earlier than that, run your numbers in two calculators that work differently, say one using the 4% rule and Clark.com’s life-expectancy model. They won’t match exactly. If they’re far apart, work out why before you trust either one, and start with the return you typed. In my experience that’s where most of the gap comes from. Once you have a number you trust, [here’s how to actually reach it](https://mycoastfire.com/blog/how-to-reach-coast-fire).

## Questions people ask

### What is the most accurate Coast FIRE calculator?

None of them can be accurate about the future, because they all assume an average return. The most honest ones let you set a return and inflation separately, add monthly contributions and choose a withdrawal rate. WalletBurst, coastfirecalculator.app, Pelcro and MyCoastFIRE all do that. Clark.com does too, except it sizes your target to a life expectancy instead of a withdrawal rate.

### Is the NerdWallet Coast FIRE calculator any good?

It's good for a fast first number. It asks for five things and fixes the withdrawal rate at 4%. There's no inflation field and no monthly contribution, so type a return that already has inflation taken out (its tip suggests 5% to 7%), and use a different tool to find out when you'll get there.

### Why do Coast FIRE calculators give different numbers for the same person?

Mostly because of how they treat returns. Some want a return before inflation and convert it, some want one after inflation, and some subtract inflation as a shortcut. Different default returns and withdrawal rates move the result too, and Clark.com uses a life-expectancy model rather than the 4% rule.

## Keep reading

-   [Coast FIRE number by ageBenchmarks from 20 to 60.](https://mycoastfire.com/coast-fire-number-by-age)
-   [Social Security and pensionsCount guaranteed income without fooling yourself.](https://mycoastfire.com/blog/coast-fire-with-social-security)
-   [Coast FIRE for couplesTwo incomes, one plan.](https://mycoastfire.com/blog/coast-fire-for-couples)