The Money Maths

Home page for all calculators.

Start here for the full set of Money Maths tools: mortgage payments, overpayments, buy-to-let yield, investment growth, EMI, step-up SIP, car depreciation, savings goals and inflation. Every calculator shows its formula, explains the terms and keeps the maths visible.

Landing page for all calculators Free, no sign-up Private by default 47 currencies

Start with the calculator that matches your goal

Mortgage repaymentSee the monthly payment, total interest and LTV.Open calculator → Savings goal trackerPlan a target date and track progress month by month.Open calculator → Car depreciationEstimate resale value and the true cost of ownership.Open calculator → Inflation and purchasing powerSee how prices and money values change over time.Open calculator →
Borrowing
Mortgage Repayment CalculatorWork out your monthly mortgage payment, total interest over the term and loan-to-value ratio. Shows the formula and a worked example. 47 currencies.Open calculator →Mortgage Overpayment CalculatorSee how much interest you save and how many years you cut off your mortgage by overpaying each month. Free, shows the maths, no sign-up.Open calculator →EMI Calculator for Personal & Car LoansCalculate the equated monthly instalment on a personal or car loan, total interest, and what it costs as a percentage of the amount borrowed.Open calculator →
Investing & saving
Investment Growth CalculatorProject what regular investing could grow into as a range of outcomes, not one smooth line. 1,500 simulations show your odds of hitting a target.Open calculator →Step-up SIP CalculatorWork out what a monthly investment grows into when you raise it each year with pay rises, compared with keeping the amount flat.Open calculator →Savings Goal TrackerSet a savings target and date, log contributions as you make them, and see whether your pace is on track. Saved privately in your own browser.Open calculator →Inflation & Purchasing Power CalculatorSee what money is really worth over time. Project how much value it loses to future inflation with an up and down band, or check how far prices have risen using real historical data for the UK, US, India, the euro area and the world.Open calculator →
Property & assets
Buy-to-Let Rental Yield CalculatorCalculate gross yield, net yield, monthly cash flow and cash-on-cash return on a rental property. Compare interest-only against repayment financing.Open calculator →Car Depreciation & True Cost of Ownership CalculatorFind what your car will be worth in 5 years and what owning it really costs per month once depreciation and running costs are combined.Open calculator →

Not sure where to start?

If you are weighing up a purchase, the depreciation calculator is the one people find most surprising — it shows the cost that never arrives as a bill. If you are saving toward something, start with the goal tracker, the only tool here that remembers your progress. Unfamiliar with a term? The glossary explains all 55 of them without jargon.

About these calculators

How the numbers are produced, what they are not, and where to get regulated advice.

How the numbers are produced

Every figure comes from a published formula shown openly in the How the maths works section, alongside a worked example built from your own inputs. Nothing is estimated, weighted or adjusted behind the scenes.

The calculations run entirely in your browser. Nothing is stored, no accounts, no tracking, no adverts, and no affiliate links to mortgage or insurance products. Nobody pays to appear here, so there is no incentive to nudge a result in any direction. The one time anything leaves your device is if you click Update to latest figures on the inflation tab — that makes a single request to the World Bank's open data API for newer price indices, and sends nothing about you. Every other figure, including the bundled inflation history, is already in the page.

Default rates and depreciation curves are typical illustrative figures, not live market data. The tools do not fetch interest rates, house prices, exchange rates or resale values from anywhere.

Limitations — read before relying on this

These are estimating tools for comparing options, not a substitute for professional advice. In particular:

· Figures exclude fees, stamp duty, early repayment charges, tax, void periods, maintenance and inflation.
· Rates are assumed fixed for the whole term; in reality fixed periods end and you revert or remortgage.
· Investment simulations assume future variability resembles the past — which markets regularly break. They show modelled uncertainty, not a forecast.
· Depreciation curves are typical patterns, not valuations. Real resale depends on mileage, condition, spec and demand.
· Changing currency relabels figures; it does not convert them.

For a decision that matters, speak to a qualified mortgage broker, accountant or FCA-regulated financial adviser. Nothing here is financial advice.

Sources & further reading

For impartial, regulated guidance in the UK:
· MoneyHelper — the government-backed free money guidance service
· MoneySavingExpert — mortgage guides and comparison tools
· Bank of England — current Bank Rate
· GOV.UK — Stamp Duty Land Tax
· FCA — checking an adviser is regulated

The amortisation, yield and depreciation formulas used here are standard published finance formulas, not proprietary methods — you are encouraged to check them against any other source.