Finance calculators

Sensible estimates for everyday money decisions. Every tool runs in your browser, shows its working, and never sells you a product. If a number here sits at the edge of what you can comfortably afford, take it as a signal to sit with the decision, not rush it.

What personal finance calculators actually solve

Most money decisions come down to one stubborn question: can I afford this, and what does "afford" mean once the headline number stops being the only number? A mortgage offer of £240,000 sounds clean until you notice the arrangement fee, the stamp duty, the survey, the searches, and the buildings insurance you have to have in place on completion day. A loan at 7.9% APR sounds reasonable until you see the total interest bill over five years. A "great" savings rate sounds great until inflation eats most of it.

A calculator is just a way of forcing those second-order numbers into the same view as the first one. That is the whole job. You enter what you know, the tool fills in what you do not, and the result is a number you can sit with for ten minutes before deciding anything.

Where to source the numbers you put in

Garbage in, garbage out applies to money more than most things. A few habits worth picking up:

  • Salary and take-home. Use your gross annual figure from your contract or P60, not what lands in your account, which already has tax taken off. The UK Salary Tax Calculator handles the conversion both ways.
  • Interest rates. Lenders publish APR on the product page, but the rate you actually get can be different once your credit file and deposit are factored in. Use the headline rate as a starting point, then run the figures again with a worse one to see how the answer changes.
  • Your real outgoings. Three months of bank statements give you a more honest baseline than what you think you spend. People underestimate food and subscriptions and overestimate fuel.
  • One-off costs. Stamp duty, legal fees, valuation, moving costs, broker fee. None of them are optional, and lumping them together as "fees" hides how much they add up to. The UK Stamp Duty Calculator breaks the band logic out properly.

Common mistakes people make with money calculators

The biggest one is planning around the best-case interest rate forever. UK fixed rates revert to the lender's Standard Variable Rate after two, three, or five years, and SVR is usually a chunk higher. If your budget only works at the fixed rate, your budget does not actually work. Run the numbers at the reversion rate too and see whether the payment is still survivable.

The second is forgetting compounding cuts both ways. A small monthly contribution to a pension or ISA over thirty years grows into something genuinely useful, which the Compound Interest Calculator shows fairly bluntly. A small monthly minimum payment on a credit card over thirty years grows into something genuinely upsetting, which the Debt Payoff Calculator shows just as bluntly. Same maths, opposite direction.

The third is ignoring inflation entirely. £500 a month in 2026 is not £500 a month in 2046. If a calculator offers a real-terms toggle, use it. If it does not, knock a percent or two off the headline return as a rough hedge.

How to choose between the tools here

If you are buying property, start with the mortgage calculator for the country you are buying in, then the stamp duty tool, then the savings goal tool to see how long the deposit takes. If you are paying down debt, the debt payoff calculator first, then the loan calculator if you are considering consolidating. If you are saving or investing, compound interest is the one. We will keep adding tools as obvious gaps show up, and the order they appear is roughly the order people search for them.

  • US Mortgage Calculator

    Work out your monthly US mortgage payment with principal, interest, property tax, home insurance, HOA and PMI broken out separately. Total interest and total cost over the life of the loan.

  • UK Mortgage Calculator

    Work out a UK monthly mortgage payment during the fixed-rate period and after it reverts to the lender's Standard Variable Rate, plus stamp duty and all the cash you need on completion day.

  • Loan Calculator

    Work out the monthly payment, total interest and total cost of any fixed-rate personal, auto or student loan. See how much you save by paying extra each month. Currency is a toggle.

  • Compound Interest Calculator

    See how a starting balance and regular contributions grow with compound interest. Optional inflation adjustment, year-by-year breakdown, currency toggle.

  • UK Salary Tax Calculator 2025/26

    Enter your gross salary to see income tax, National Insurance and student loan deductions broken down, plus take-home by year, month and week. England, Wales and Northern Ireland rates.

  • UK Stamp Duty Calculator 2025/26

    Calculate Stamp Duty Land Tax for a residential purchase in England or Northern Ireland. Covers standard purchases, first-time buyer relief and the additional property surcharge. Shows the full band breakdown.

  • Debt Payoff Calculator

    Work out how long it takes to pay off a credit card, loan, or overdraft at a fixed monthly payment. Add an extra monthly payment to see exactly how much time and interest you save.

  • Tip Calculator

    Work out the tip, split the bill, and optionally round each person up to a whole number so nobody has to fish out coins at the end of the meal. Currency toggle covers USD, GBP, EUR, CAD and AUD.

  • Savings Goal Calculator

    Work out the monthly number you need to hit a savings target by a specific date. Factors in your starting balance and the interest your account pays. Sets a sensible target for a wedding, a deposit, a rainy-day fund or a long holiday.

Frequently asked questions

Are these UK or US finance calculators?

Both, side by side. Tools prefixed with "UK" (UK Mortgage, UK Salary Tax, UK Stamp Duty) use HMRC bands, UK conveyancing rules and pound sterling. The generic tools (Compound Interest, Loan, Debt Payoff, Savings Goal, Tip) are currency-agnostic and work for any country: type whatever currency suits, the maths is the same. The mortgage calculators are clearly labelled so you do not pick the wrong one for your situation.

How accurate are these figures versus what my lender or HMRC will actually quote?

Close, but not identical. The UK Mortgage Calculator uses standard repayment maths and the rate you supply, but a real lender will also factor in product fees, early repayment charges, valuation fees and any cashback, none of which a generic tool can know about. The UK Salary Tax Calculator uses the current year's tax bands, National Insurance thresholds and standard personal allowance, but it cannot know about marriage allowance transfers, tax codes from prior years, salary sacrifice arrangements or benefits in kind. Use the numbers here for planning. Use a quote from your lender or HMRC's official tools for decisions that have to be exact.

What is the difference between APR and the interest rate?

The interest rate is what the lender charges on the borrowed money. The APR (annual percentage rate) is the interest rate plus the fees and charges, expressed as a single annual figure so different products can be compared like for like. APR is always equal to or higher than the headline interest rate. When the gap between the two is large, the product is loaded with fees. When it is small, the rate you see is close to what you actually pay.

Should I overpay my mortgage or invest the difference?

The honest answer is "it depends on your mortgage rate versus your expected investment return after tax, both of which are uncertain". As a rough rule, overpaying a fixed-rate mortgage above 5 per cent is a guaranteed return that is hard to beat with most low-risk investments. Below 3 per cent, a stocks-and-shares ISA has historically done better over long periods, but with real risk attached. The Compound Interest Calculator shows the investing side; the UK Mortgage Calculator shows the overpayment side. Run both with realistic numbers and compare.

Does my financial information leave the browser?

No. Every finance calculator on this site runs entirely in JavaScript on your device. Salary, mortgage balances, savings amounts, none of it is sent anywhere. You can disconnect from the network and the tools still work. Nothing is stored, logged or transmitted.

Why split US and UK into separate tools

Mortgages look similar across countries but the mechanics diverge quickly. A US mortgage is usually fixed for the entire term, PMI kicks in below a 20% deposit, and escrow wraps tax and insurance into the monthly payment. A UK mortgage is usually fixed for only two, three, or five years before reverting, with an arrangement fee, stamp duty up front, and no PMI equivalent. A single "one size fits all" mortgage calculator glosses over those differences in a way that is genuinely unhelpful.

So we do two: a US one here, and a UK one alongside it. Each uses the terms, thresholds, and fees of its own market, so the number you see is one you can actually use.

Business finance tools have moved

ROI calculators, VAT tools, and anything framed around a business decision now live in the Business calculators section. This section covers personal finance: mortgages, loans, savings, and take-home pay.

Nothing here is financial advice

These are sensible estimates for back-of-envelope decisions. For a real loan or tax situation, talk to a broker, loan officer, or accountant who knows your full picture.