Free · No bank linking · Maths shown
Know the day you're free.
FireMathLab turns your savings, debts and spending into dates you can plan around: the year you could stop working, the month you clear the cards, the point your pot pays your bills.
No account needed to use any calculator. Sign up only to save and track.
See what it does
Four of the tools, cycling. Hover to pause, or jump straight in.
The year work becomes optional
Project savings month by month to the point investment income covers your spending. Then watch the date move as you change one input.
Open FIRE calculator →Start with a question
Each calculator answers one thing properly, shows the formula behind it, and tells you where the model stops being reliable.
FIRE Calculator
Find the year work becomes optional
Project your savings month by month to the point where investment income covers your spending. Adjust age, contributions, returns and target spending, and watch the freedom date move in real time.
Coast FIRE Calculator
The day your pot can grow on its own
Coast FIRE is the moment your existing savings would reach your target by retirement age with no further contributions. This finds that crossover age and what it would take to bring it forward.
Barista FIRE Calculator
Part-time work, full-time freedom
Model a semi-retirement phase where part-time income covers some of your spending while the portfolio keeps growing. See how many years of full-time work that trade removes.
Safe Withdrawal Rate Explorer
How much can you actually take?
Compare withdrawal rates from 2% to 6% against both simulated and historical outcomes, and see how the choice changes the pot you need and the risk you carry into retirement.
Monte Carlo Retirement Simulator
A thousand possible futures
Markets do not deliver an average return every year. This runs your plan through a thousand randomised return sequences and reports how many of them still had money at the end.
Historical Backtest
Your plan against real market history
Replay your plan against every starting year since 1900 using historical real returns. It answers a sharper question than averages do: would this plan have survived the actual past?
Market Crash Stress Test
Retiring the day everything falls
Sequence-of-returns risk in a single number: what happens to your plan if a 35% crash lands in the first year of retirement and returns never recover to your assumption.
Rich, Broke or Dead
The outcome most calculators ignore
Overlays mortality on your projection, so each future year is split three ways: still investing, alive but out of money, or no longer here. It reframes "one more year" honestly.
Withdrawal Strategy Comparator
Fixed, percentage, or guardrails
Compare a fixed real income against percentage-of-portfolio withdrawals and Guyton-Klinger guardrails, and see the trade between steady spending and never running out.
FIRE Date Sensitivity
Which lever moves your date most
Nudge each input up and down in turn and rank them by how many months they move your freedom date. Usually the answer surprises people: it is rarely the return assumption.
Pension Bridge Calculator
Covering the years before pensions unlock
If you stop work before your pension is accessible, only some of your money can be spent. This checks whether your accessible pots can carry you to the unlock age without running dry.
Couples FIRE Calculator
Two ages, two incomes, one date
Household planning with two different ages and contribution levels, including how a partner’s pension access age and life expectancy change the joint picture.
Debt Payoff Planner
Snowball against avalanche, with real numbers
List every debt, then compare paying smallest-balance-first against highest-interest-first. Shows the debt-free date, total interest, and what an extra payment each month buys you.
Rent vs Buy Calculator
How long you must stay for buying to win
Compares renting and buying on equal footing: stamp duty, maintenance, selling fees, and the return the deposit would have earned invested. The answer is a break-even year, not a monthly payment.
50/30/20 Budget Planner
Needs, wants and savings in proportion
Splits your take-home pay across needs, wants and saving, and shows the size and direction of every gap. Minimum debt payments count as needs; only overpayments count as saving.
Mortgage Overpayment Calculator
Years and interest an overpayment saves
See how regular overpayments shorten the term and cut total interest, then compare that guaranteed return against investing the same money instead.
Savings Goal Calculator
When will you get there?
Set a target and a monthly amount and get the month you reach it, with interest separated from contributions so you can see how much of the goal the bank is paying for.
52-Week Savings Challenge
The classic, with a tracker
Save a rising amount each week for a year. Pick your multiplier to set the difficulty, then tick weeks off as you go and watch the total build toward the finish line.
Emergency Fund Calculator
Three months, six, or something else
Size a cash buffer from your actual monthly essentials and circumstances (job security, dependants, income stability) rather than a one-size rule of thumb.
Net Worth Tracker
One number, tracked monthly
Add your accounts once, then log balances each month. Assets minus debts, charted over time, with your own notes against the months that moved.
Net Worth by Age
Where you stand, and why it barely matters
Compare your net worth against typical figures for your age band, and read the caveats, because medians hide enormous variation in property, pensions and inheritance.
Savings Rate Calculator
The only number that really sets the date
Your savings rate (income minus spending, over income) determines the years to financial independence almost on its own. Enter both and see the years fall out.
25× Rule Calculator
Your FIRE number in one step
Annual spending multiplied by 25 is the shorthand for the pot a 4% withdrawal rate supports. Enter your spending for the number, and see how other rates change it.
Pot to Income Calculator
What does a pot actually pay?
The 4% rule in reverse: enter a pot and get the monthly income it could sustain, at whichever withdrawal rate you consider safe.
Compound Interest Calculator
Growth, contributions, and time
The engine underneath every other tool here: starting balance, regular contributions and a growth rate, projected forward with the interest separated from what you put in.
Investment Fee Calculator
What a 1% fee really costs
Platform and fund fees compound against you. This converts a percentage into the money lost over your investing life, and the extra months of work it represents.
Inflation Calculator
Today's money versus future money
Convert between real and nominal amounts so a projection means something: £1m in 2050 is not £1m today, and every plan here is quoted in today’s money for that reason.
Payday Allocator
Give every pound a job, the day you are paid
Split one paycheck into bills, debt payments, goals, investing and what is genuinely safe to spend. A two-minute routine to run the moment your salary lands.
Subscription Audit
What your recurring bills really cost
List every recurring charge to see the annual total, spot the ones whose price has crept up, and find what cancelling one is worth if redirected at your mortgage or portfolio.
Cash Flow Calendar
The next 30 days, not the next 30 years
Map income and bills across a month to find the dip days, when several bills land before the next payday, and move a transfer before it costs you an overdraft fee.
Sinking Funds Planner
Turn once-a-year costs into a monthly number
Car insurance, Christmas, the boiler service, the renewal you always forget. Set the yearly targets and get the monthly amount that stops them wrecking a budget.
Expense Diary
Log what you spend, see where it goes
A daily spending log with a category breakdown. Free, no bank connection, no sign-up to try, and a full ledger with bills, balances and safe-to-spend once you have an account.
How it works
Put in your real numbers
Type what you have, save and spend. Nothing connects to your bank, so there are no credentials to hand over and no transaction feed to leak.
See the date, not just a total
Every projection resolves to something you can act on: the year work becomes optional, the month a debt clears, the balance a goal needs.
Check in monthly
Create a free account to save plans and log your net worth each month. The trend is what matters, and it only exists if you record it.
Why these numbers are worth trusting
🎲 It admits what it cannot know
A single projected date assumes markets deliver the same return every year, which they never do. So every FIRE plan can also be run through a thousand randomised return sequences, replayed against market history since 1900, and stress-tested against a crash landing in your first year of retirement.
📐 The formula is on the page
Each tool explains its own arithmetic in plain English (how the withdrawal rate sets your target, why monthly compounding uses the twelfth root rather than dividing by twelve) and lists the assumptions that would make its answer wrong.
🔒 Manual entry, on purpose
Nothing here connects to a bank. Typing six numbers once a month takes four minutes and means there are no credentials to hand over, no permanent read of your transactions, and nothing to sell.
🧭 Guidance, never advice
These are educational models, not recommendations. They are built to help you understand the shape of a decision; the real one belongs to you, ideally with a qualified adviser alongside.
Your freedom date is a calculation away
Start with the FIRE calculator. It takes about a minute, and you can decide afterwards whether you want to keep track.
Run the numbers