Net Worth Projection Calculator

What this calculator does

This calculator projects your net worth forward. Starting from your current assets and debts, it applies your monthly savings, a growth rate on assets, and your monthly debt payments across a chosen number of years, returning projected net worth alongside the asset and debt balances at the end.

Splitting the answer into final assets and final debts is what makes it useful. A single ending figure hides whether the improvement came from building assets or clearing liabilities, and those two routes call for different decisions. Seeing both lines shows you the year the mortgage disappears and the year returns start outweighing your contributions.

When to use it

Use it for medium and long horizon planning — testing whether your current savings rate reaches a target in twenty years, working out when you might realistically be mortgage free, or checking whether retiring earlier is arithmetically possible.

It also resolves trade-offs that are hard to reason about in the abstract. Running the same starting position with £800 a month of savings against £1,100, or a 4 percent growth assumption against 6, turns an argument into two numbers. It is less useful over short horizons: across three years, market variation swamps everything the model captures.

Understanding the inputs

Total assets and total debts set the starting point, at current market and settlement values. Monthly savings added is new money going into assets each month — the genuine surplus after all outgoings, including employer pension contributions if you are counting pensions as assets.

Asset growth rate should reflect your actual mix. Six to seven percent suits an equity-heavy ISA and pension portfolio, 4 to 5 a balanced one, and 3 to 4 is more realistic where property equity dominates. Monthly debt payments reduce the debt balance until it reaches zero. Years is the horizon — run several, because the shape of the curve teaches more than any single endpoint.

How is this calculated?

Net Worth(year n) = Current × (1+r)^n + Annual Savings × [(1+r)^n − 1]/r

A worked example

Start with £250,000 of assets and £180,000 of debts, giving a net worth of £70,000. Add £800 a month to assets, assume 5 percent growth, and pay £900 a month toward debt over twenty years.

Assets grow to roughly £981,000, while debts clear entirely in year seventeen at £10,800 a year. Projected net worth is therefore about £981,000, against £70,000 today. Of the £911,000 gain, your own money accounts for £192,000 of contributions plus £180,000 of debt payments, so growth supplied close to 60 percent. In today's purchasing power at 2.5 percent inflation, however, £981,000 is closer to £598,000 — which is why running the projection in real terms is worth doing alongside.

Limitations and assumptions

The model applies one flat growth rate every year. Real markets deliver sequences rather than averages, and a 5 percent long-run assumption can conceal a decade that returned 1 percent. Past performance does not predict future returns, and a twenty-year projection is a scenario, not a forecast. This is not regulated financial advice.

It also assumes savings and debt payments never change, no major purchases or sales occur, and no life events intervene — redundancy, a house move, children, divorce, or ill health will all reshape the curve. Debt reduces by your payment amount without interest being modelled, so high-rate debt clears faster here than in reality. Figures are nominal and exclude tax on gains outside an ISA.