What it is

Drawdown Simulator answers the question most people approaching retirement actually have: will the money last, and what will the tax look like along the way? You enter what you have (pensions, ISAs, savings), when you want to stop, and what you want to spend. It runs your plan through 1,000 simulated market futures, year by year, with UK income tax worked out per person, the State Pension, inflation and the 25% tax-free cash rules, and tells you in how many of those futures every year to your target age was funded. Then it reads the plan back to you as a story, and lets you compare it with the ordinary alternatives: work longer, spend less, secure the essentials with guaranteed income.

It is a UK tool. Defaults use the 2026/27 tax year, Scottish rates are supported, couples get two personal allowances, and the April 2027 change bringing unused pensions into inheritance tax is built in. Everything runs in your browser. Nothing you enter is sent to a server.

Who built it

Oliver Bridges, who works in data and is not a financial adviser. It began as a spreadsheet for his own retirement, became a web tool when friends could not follow the spreadsheet, and has grown since through readers writing in with what it could not do. Most of the features added in 2026 started as an email from someone reading their own numbers line by line. Corrections go in with credit; the changelog records them.

What problem it solves

Most retirement calculators give one number from one average return. Real retirements do not get the average; they get a sequence, and a bad sequence early can sink a plan that the average said was fine. This tool shows the spread of outcomes rather than one line, keeps the tax honest year by year, and puts the decisions people actually face (when to stop, how much to spend, whether to buy certainty) side by side on the same simulated futures so the differences are the decision, not chance.

How it works, briefly

Annual steps from the retirement date. Each year it works out the income needed, draws it in the order you chose, taxes each person's withdrawals against that year's bands, applies the State Pension when it starts, and grows what is left at a return drawn from the distribution you set. It repeats that for 1,000 futures and reports the share in which the plan was funded to the end. The full description, including what "works in 90 of 100 futures" does and does not mean, is on the methodology page.

What it does not do

It does not give advice or recommend products. It shows what changes if you change something.
It does not model your salary, the care means test, emergency tax on a first withdrawal (deliberately, since it is reclaimed), overseas tax, defined benefit transfer values or lifetime allowance protections.
It uses normally distributed returns by default, which understate the worst tails; the 1973, 2000 and 2008 historical overlays are the stand-in for that.
It cannot know your health, your family or your appetite for risk.

Is it advice?

No. It is a planning tool built by someone who is not a financial adviser, and it says so on every page. MoneyHelper and Pension Wise are free and impartial; a regulated adviser can recommend specific products. The tool's job is to make the conversation with any of them better informed.

How current it is

Tax rates and thresholds are those legislated for 2026/27, with the threshold freeze to April 2031 and statutory indexation after it, and the Finance Act 2026 change to pensions and inheritance tax from 6 April 2027. The engine is under version control with a regression suite of golden fixtures, and every change that moves a number is recorded in the changelog with the date. The current version is 1.40.

Get in touch

Spotted something off, or want a feature? Email hello@drawdownsimulator.co.uk. Firms interested in the engine or the story format should read the for firms page.

About Drawdown Simulator