Category
Tools
Companion guides to every calculator on the site - how each works, what numbers actually matter, and how to read the output.
The site has free calculators for the maths that actually shapes a financial plan: compound interest, FI number, safe withdrawal rate, drawdown survival, debt snowball vs avalanche, mortgage overpayment, take-home pay, stamp duty. Each one has a written guide that explains what the tool does, what the inputs really mean, and how to interpret a result that doesn't look how you expected.
These articles are useful in two situations. First, when a calculator gives you a number that feels wrong and you want to understand the assumptions behind it. Second, when you want a worked example before opening the tool yourself.
Start with the compound interest guide for the foundational maths, the drawdown calculator if you're modelling retirement, or debt payoff if you're choosing between snowball and avalanche.
15 articles
Showing 1-10
Emergency Fund Calculator: Target and Time-to-Goal
Your emergency fund has a sweet spot most calculators don't flag. Cross it and HMRC quietly takes a 40% bite of the interest. The number to know before you pick the account.
Redundancy Pay UK: How Much Will You Get?
The redundancy number in the letter is not the number that hits your account. A statutory cap, a PILON tax trick and a holiday-pay catch shave thousands off before you see it.
Stamp Duty Calculator UK: How Much Will You Pay?
Your first-time-buyer stamp duty relief ends at £500,000. Stretch £11k over the line and the entire purchase gets repriced. The cliff edge nobody warns you about before you offer.
Invest vs Pay Off Mortgage Calculator UK
Overpay or invest? The rule of thumb everyone quotes ignores the wrapper your money sits in. Plug in your real rate, tax bracket and ISA headroom and the answer often flips.
Life Plan Calculator: Map Your Entire Financial Future
Most retirement calculators ask one question at a time. Real life refuses to. The one that finally models every pot and wrapper together, and tells you when the plan breaks.
Drawdown Calculator UK: Will Your Pot Last?
The hardest financial question in retirement isn't 'have I saved enough?' It's 'how long will what I have actually last?' The drawdown calculator answers that, year by year.
Coast FIRE Calculator: Stop Saving and Still Retire
Coast FIRE is the only number that lets you stop saving in your 30s without breaking the maths. The age you hit it depends on one variable, and it's not your income.
Debt Payoff Calculator UK: Snowball vs Avalanche
Snowball or avalanche? The maths almost always favours avalanche - but the strategy you'll actually finish beats the one that's £200 cheaper on paper. The calculator settles it.
Take-Home Pay Calculator UK: What You Actually Earn
The salary on your offer letter is a fiction. Four deductions chew it down before the money lands. Budgeting from the headline is why so many UK households feel poor on good pay.
Compound Interest Calculator: How It Works
Einstein supposedly called compound interest the eighth wonder of the world. The wonder isn't the maths. It's what 30 years of nothing does to £10,000.