Understand your Financial Independence Year

Ambit explains the assumptions behind your Financial Independence Year: spending, saving, returns, invested assets, and your portfolio target. It helps you read the estimate in plain language, without advice.

Learn the assumptions behind the year, without advice.

Create your FI Year

Learning paths

Learn the assumptions behind the year

Start with the assumption closest to your question. Each path explains the concept, why it matters for the Financial Independence Year, and what to read next.

Choose an assumption path. Read one concept at a time.

Start with Financial Independence YearFIRE Calculator UKUse Undefeated to estimate your Financial Independence Year: the first year projected assets meet the spending threshold and the duration requirement, based on the assumptions you enter.Create your FI Year
Explore all learning paths4
Start

Understand your FI Year

See how spending, savings, and assumptions turn into the year work becomes optional.

FIRE calculator UKFIRE Calculator UKUse Undefeated to estimate your Financial Independence Year: the first year projected assets meet the spending threshold and the duration requirement, based on the assumptions you enter.
Retire questionWhen can I retire? Start with the year work could become optional.State Pension age is a separate rules question. Undefeated estimates the year work could become optional from the assumptions entered.
Inputs

See what retirement depends on

Read the plain questions with the inputs behind the answer in view.

Retirement amountHow much do I need to retire in the UK?This page explains how annual spending, the portfolio target, and the projected invested amount connect to one capital check behind a Financial Independence Year. The calculation also tests a separate duration requirement. It is educational only and does not tell you how much to invest.
Retire earlyEarly retirement estimates still depend on the inputs.Early retirement here means an earlier work-optional year based on assumptions, not a State Pension age rule.
Target

Learn the target number

Understand how annual spending and the portfolio target shape one amount behind the year.

FIRE numberFIRE Number Calculator: understand the target behind your year.A FIRE number is the portfolio target amount, one of two capital checks behind the Financial Independence Year. It comes from annual spending and the selected portfolio target; projected invested assets are tested against it and the separate duration requirement.
Monthly spendingMonthly spending sets the size of the target.Monthly spending is annualised for both the spending threshold and the duration requirement.Withdrawal rateWithdrawal rate turns spending into a target portfolio.Undefeated sets the spending-based check with a portfolio target. For context, 25x annual spending is mathematically equivalent to a 4% spending-to-portfolio ratio. The separate duration requirement still applies.Safety bufferSafety buffer adds margin, not certainty.Undefeated does not ask for a separate safety-buffer input. Any extra headroom in the spending-based check is expressed through the selected portfolio target.
Time

Understand time and compounding

Learn how invested assets, savings, and return assumptions can change the year.

Coast FIRECoast FIRE is about time, invested assets, and assumed growth.The Coast milestone in Undefeated uses your Financial Independence Year and current inputs. Ambit explains the assumptions behind the idea.
Compound interestCompound Interest Calculator UKUse this UK compound interest calculator to see how starting amount, monthly contributions, time, and a nominal or real return assumption can shape a future pot. It does not calculate when work becomes optional; Undefeated’s main calculator turns assumptions into your Financial Independence Year.Monthly savingsChanging monthly savings affects when the target may be reached.Monthly savings is the investable amount added during each projected year.Expected real returnExpected real return shows assumed growth after inflation.Expected real return is the after-inflation growth rate used for invested assets. It is the place to think about nominal returns, inflation, fees, and investment mix before the assumption enters the Financial Independence Year.