Life Plan Calculator

What the Life Plan calculator does

The Life Plan calculator runs a year-by-year cashflow model of your entire financial life. Salary trajectory, expenses, ISA, GIA, LISA, workplace pension or SIPP, mortgage or rent, student loan, defined-benefit pensions, and the State Pension are all wired together in one simulation. Each year the model grows your income, pays your tax, settles your housing and living costs, allocates whatever is left into the right wrappers, and grows your invested pots by the expected return.

It is built for the messy reality of UK personal finance, where a private pension is locked until 57, a LISA until 60, and the State Pension does not start until 67 or 68. Most calculators ignore the gaps between those ages. The Life Plan calculator does not. It shows you whether your ISA can actually carry you from your retirement date to your pension access age, and whether your pension can carry you the rest of the way until the State Pension arrives.

Why this is different from a FI number calculator

A FI number calculator answers one question: how much do you need invested to cover your expenses forever at a chosen withdrawal rate. That is a single number, useful as a target, but it does not tell you whether the path to that number is feasible. It assumes a smooth career, a single pot, and a constant return.

A Life Plan calculator answers a different question: in which year of your life does the plan actually break. It is a cashflow model, not an end-state target. It models every pot separately, respects the age-locked access rules, factors in mortgage payoff, and tracks the running balance year by year. The FI number is the destination. The life plan is the road. You need both, and the road is the part most people get wrong.

Broke-period detection and the bridging strategy

The most useful output of the calculator is the broke-period detection. After retirement, the model draws down from your accessible pots in order: emergency fund, ISA, GIA, LISA from 60, then private pension from your access age. If any of those pots empties before the next one unlocks, the chart shades that range red and the phase card flips to amber or red. That shaded band is the gap in your plan. It tells you, precisely, which years of your life the current plan does not cover.

This is the bridging problem made visible. If you want to retire at 50 and your pension does not unlock until 57, you need seven years of accessible money in your ISA, GIA, and emergency fund. If the model shows you running out at 54, you have two useful levers: shift contributions away from your pension and into your ISA, or push your retirement age out. Without the year-by-year model, that trade-off is invisible. See our Coast FIRE calculator for the related question of when your existing pots are large enough to compound to the target without further contributions.

How to read the chart

The net worth chart stacks each pot in a different colour. Pension sits at the bottom in blue, ISA in amber, GIA in teal, LISA in pink, and the emergency fund in grey. Mortgage and student loan balances sit below the zero line in red. Watch for two things: the rate at which your accessible pots (ISA, GIA, LISA) build during your working years, and the rate at which they deplete after retirement. The handoff to your pension at 57 should be visible as the pension stack flattening or shrinking while the ISA and GIA stacks drop sharply. If the accessible stacks hit zero before the pension takes over, the red shaded band shows exactly when.

The passive income chart is the second one to watch. The crossover point where investment income overtakes expenses is your true FI date. Step-ups at pension access and State Pension age appear as visible jumps. If the income line never crosses expenses, the plan is not funded at the chosen retirement age regardless of what your total net worth says.

Stress-test the assumptions, because real careers are not smooth

The average UK retirement projection assumes a smooth career: same salary growth every year, no income discontinuities, no career break, no redundancy. Most workers have at least one of those. Parental leave costs years of pension contributions. Redundancy at 45 can wipe out three years of saving while you find work at a lower grade. A career break to retrain pulls qualifying years off your State Pension. None of that is a personal failure. It is the modal experience of a UK worker, and a plan that does not survive any of it is a plan that pretends workers are interchangeable widgets in a spreadsheet.

Use the calculator to stress-test. Drop your salary growth to 1% and check the outcome. Set a five-year period at 60% of your current expenses to model parental leave. Push your retirement age out by two years and see what your ISA looks like at 55. A plan that only works if the next 35 years are perfect is not a plan, it is a wish. A plan that survives one or two bad scenarios is closer to honest.

UK-specific nodes: State Pension, LISA, and ISA versus SIPP sequencing

The State Pension is modelled using the triple lock - the higher of inflation, wage growth, or 2.5%. Qualifying years are calculated from the age you started working to your retirement age, with 35 needed for the full pension and 10 the minimum for any entitlement. Your State Pension age is derived from your birth year: 68 for those born after 1977, 67 for 1961-1977, and 66 for earlier. A career break that drops you below 35 qualifying years reduces your State Pension proportionally, and the calculator reflects that.

The LISA is worth taking seriously in your 20s and 30s. The 25% government bonus on contributions up to £4,000 a year is one of the highest-return moves available to a UK worker, capped at £1,000 a year of free money until age 50. The calculator allocates surplus to the LISA before topping up your pension or filling your ISA, because the bonus beats almost any other allocation on a risk-adjusted basis. Funds unlock at 60, so the LISA sits between the ISA bridge and the pension drawdown phase.

The ISA versus SIPP sequencing question is the one most readers get wrong. The default UK personal finance advice is to max your pension for the tax relief. That is good advice if you plan to work to 67. If you plan to retire at 50, it is bad advice, because you cannot touch your pension until 57. The model lets you set savings phases with either ISA priority or pension priority, and the right answer for most early retirees is ISA priority until the bridge is funded, then pension priority once the bridge is solid. Check your take-home pay to see how much you can realistically allocate before running the sequencing scenarios.

Frequently asked questions