Retirement Planning That Actually Uses Your Numbers

Most retirement calculators work like this: you enter your age, your savings, an expected return, and maybe a retirement age. The calculator runs some maths and gives you a number. "You'll have £1.2 million at 60." Or "you need to save £800 more per month." You nod, close the tab, and nothing changes.

The problem isn't the maths. The maths is fine. The problem is that those calculators don't know anything about your actual financial life. They don't know your mortgage finishes in 2038 and your expenses drop dramatically after that. They don't know you plan to go part-time at 55 before fully retiring at 60. They don't know about the rental income that kicks in next year, or that your partner's pension starts at a different age from yours.

Real retirement planning, whether you're aiming for traditional retirement at 65 or financial independence at 45, has phases. Your income changes. Your expenses change. Your tax situation changes. A single-number calculator can't capture any of that.

That's why we built the Retirement Planner in Endute.

What it does

The Retirement Planner lets you build a multi-phase plan that mirrors how your financial life will actually unfold. Each phase represents a distinct period: maybe "Working full-time" from now until 50, "Part-time consulting" from 50 to 55, and "Fully retired" from 55 onwards. Each phase has its own income sources, its own budget, and its own set of accounts you're drawing from or contributing to.

You define as many phases as you need. Two is fine. Five is fine. The planner stitches them together into a single projection that runs month by month from today through to the end of your plan.

This is the core difference from a typical FIRE calculator. Instead of one growth rate, one savings rate, and one spending number, the planner models the transitions that actually define your path to retirement.

Projections grounded in your real data

The planner doesn't ask you to guess your current portfolio value or estimate your monthly spending. It already knows both, because it pulls from your Endute accounts. Your investment balances, your bank balances, your actual spending patterns. The projection starts from where you actually are, not where you think you are.

Each phase lets you set income sources (salary, rental income, pension drawdown, state pension), a budget for that phase, and which accounts fund it. Growth rates and inflation are configurable per phase. If you expect your investments to return 6% while you're working and shift to a more conservative 4% in retirement, you set that directly.

The output is a month-by-month projection chart showing your portfolio value over time. You can see exactly when your money runs out, or whether it doesn't. You can see how your spending and income interact across phase boundaries.

Monte Carlo: what the range of outcomes looks like

A single deterministic projection is useful but misleading. It shows you one path through the future, and that path assumes your investments return exactly 6% every year. They won't. Some years will be up 20%, others down 15%. The order of those returns matters enormously, especially in the years right around retirement. This is what the FIRE community calls sequence-of-returns risk, and it's the reason people with identical average returns can end up in completely different financial positions.

The Monte Carlo simulation runs your plan through thousands of randomised return sequences drawn from historical market data. Instead of one line, you get a distribution. The result tells you the probability that your plan succeeds across a wide range of market conditions.

We show the 10th, 25th, 50th, 75th, and 90th percentile outcomes so you can see the full spread. A plan that works at the median but falls apart at the 10th percentile has a very different risk profile from one that holds up across the board. Seeing the range is what turns a guess into something you can actually make decisions from.

Historical backtesting

Monte Carlo uses randomised sequences. The backtest uses actual ones. It takes your plan and asks: what would have happened if you'd started this plan in 1950? In 1970? In 2000?

Each starting year runs through the real stock returns, bond returns, and inflation rates from that period forward, using Shiller's monthly US market data. This captures real events: the stagflation of the 1970s, the dot-com crash, the 2008 financial crisis, the recovery that followed.

The result is a grid showing your plan's outcome for every possible starting year. You can see which historical periods would have been worst for your specific plan, and by how much. It's a different kind of stress test from Monte Carlo, because the return sequences aren't random. They happened. And one of them might look a lot like whatever the next decade throws at us.

What-if explorer

Once your plan is set up, the what-if explorer lets you tweak variables and see the impact in real time. Drag a slider to increase your spending by 10%. Reduce your growth rate. Push your retirement age forward by two years. Add a lump sum event.

The projection updates as you move the sliders, so you can develop an intuition for which variables matter most. For most plans, the answer is some combination of how much you save in the early years, what return you get in the decade before retirement, and how much you spend once you stop working. But the relative importance varies, and the what-if explorer is where you figure that out for your specific situation.

Sensitivity analysis

The sensitivity analysis is related but more structured. It takes five key variables (income, growth rate, inflation, tax, and plan horizon) and perturbs each one by plus and minus 10%. The result is a tornado chart showing which variable has the biggest impact on your outcome.

This is useful for knowing where to focus your energy. If your plan is highly sensitive to growth rate but barely moves when you adjust the tax rate, you know that getting your asset allocation right matters more than optimising your tax wrapper. If it's the other way around, different priority.

Monitoring: plan vs reality

A plan is only useful if you track whether you're on course. The monitoring section compares your plan against what's actually happening.

When you lock a plan version (saying "this is my baseline"), the planner captures a snapshot of your portfolio at that point. From then on, it compares your actual account balances and savings rate against what the plan projected. If your portfolio has drifted ahead of plan, you'll see a positive delta. If it's behind, you'll see how far.

There's also a savings rate tracker that pulls from your real transaction history, showing your actual savings rate over rolling 3, 6, and 12-month windows. This is one of the most useful views, because savings rate is the variable you have the most direct control over.

If your plan drifts significantly from the baseline, the planner nudges you to re-lock to a new baseline so you're always working from current reality, not a stale snapshot.

Not just for FIRE

We've called this the "Retirement Planner" rather than a "FIRE calculator" because it works for anyone thinking about their financial future, not just people pursuing early retirement.

If you're 55 and want to understand whether you can afford to retire at 62, this is the tool for that. If you're 30 and curious about what aggressive saving now buys you in optionality by 50, same tool. If you want to model the impact of taking a career break at 40 and returning to work afterwards, the multi-phase structure handles that without workarounds.

The FIRE community will recognise the concepts: safe withdrawal rates, sequence-of-returns risk, Monte Carlo success rates. But you don't need to know any of that terminology to use the planner. Define your phases, set your income and expenses, and let the projection show you what the numbers say.

Limitations to know about

The planner currently runs on the web app only. Mobile support will follow in a future update.

It doesn't model tax in detail. You can set an effective tax rate per phase, and the planner applies that to your income, but it doesn't model ISA allowances, pension annual allowances, or the interaction between different tax wrappers. That level of tax modelling is country-specific and complex enough that we didn't want to hold the rest of the feature for it. It's something we're considering for the future.

State pension is modelled as an income source you add manually with a start date matching your state pension age. We don't pull state pension forecasts automatically.

Getting started

The Retirement Planner is available now in the web app under FIRE Planning in the sidebar. Start by creating your first plan and adding at least two phases. Set your income and budget for each phase, choose which accounts fund each one, and run the projection.

From there, try the Monte Carlo simulation to see how your plan holds up across different market environments, and use the what-if explorer to stress-test your assumptions. Lock a version as your baseline when you're satisfied with it, and check back on the monitoring page over time to see how reality lines up against the plan.