Financial calculators that show their formula

Calculators

• Saving & interest

  Compound interest calculator

  See how a starting amount and monthly contributions grow with compound interest, with an open formula, a year-by-year table and worked examples in your browser.

• Saving & interest

  Savings goal calculator

  Work out any of five figures for a savings plan: the final balance, the monthly amount to reach a goal, how long it takes, the starting sum or the rate needed.

• Saving & interest

  Inflation calculator

  See how inflation erodes money both ways: what a sum today is worth later, and what a future sum is worth in today's money — loss shown in your currency and per cent.

• Drawdown & planning

  Withdrawal plan calculator

  See how long your capital lasts at a fixed monthly withdrawal, or how much you can withdraw over a set number of years. With a yearly trajectory, in your browser.

• Budget & reserves

  Emergency fund calculator

  Work out how big your emergency fund should be and when you'll have it: set your own months of cover and see the target, the gap, progress and time to reach it.

• Budget & reserves

  Household budget calculator

  Plan a monthly budget: enter income and expenses to see the balance, your savings rate and how spending splits — with an optional 50/30/20 check, in your browser.

• Budget & reserves

  Savings rate calculator

  Work out your savings rate from income and what you save — or the amount a target rate needs — and see the long-run effect of saving one point more.

• Saving & interest

  Savings interest calculator

  See the interest and final balance a savings deposit earns at a rate you choose — easy-access or fixed-term, with a compounding schedule and effective annual rate.

• Investing & returns

  Fund fees calculator

  See how an ongoing charge and other fund fees quietly eat into an investment over the years — your own assumptions, no product data, all in your browser.

• Investing & returns

  CAGR calculator

  Work out total return, the annualised return (CAGR) or a target value from a start and end value — no interim cash flows, neutral and in your browser.

• Saving & interest

  Real return calculator

  Work out your real return after inflation and fees with the exact Fisher relationship — and see how far the 'nominal minus inflation' rule of thumb is off.

• Drawdown & planning

  Financial independence calculator

  Work out the capital your desired withdrawal needs over a horizon you choose — and when you would reach it. A deterministic real-value model, in your browser.

• Investing & returns

  Dividend calculator

  Work out a dividend yield, project payouts at an assumed growth rate and see how reinvestment compounds shares — with yield on cost, neutral and in your browser.

• Investing & returns

  Lump sum vs phased investing calculator

  Compare, neutrally, what investing a sum all at once or spreading it over months gives at your assumed return — no recommendation, all in your browser.

• Investing & returns

  Average cost calculator

  Work out the weighted average price you paid across several purchases, with and without fees, plus an optional unrealised gain or loss — neutral, in your browser.

• Cars & mobility

  Fuel cost calculator

  Work out fuel or electricity cost per trip, month and year — with your own consumption and price, cost sharing, commute mode and a scenario comparison.

• Property & housing

  German property purchase costs calculator

  Estimate the extra costs of buying property in Germany — land transfer tax, notary, land registry and estate agent — with your own rates, in EUR, in your browser.

• Cars & mobility

  Car running costs calculator

  Work out a car's real running costs — depreciation, insurance, tax, servicing, repairs, tyres and energy — per month and per km, with an A/B comparison.

• Property & housing

  Rent vs buy calculator (Germany)

  Buy, or rent and invest the difference? A neutral wealth comparison of both paths for the German market — year by year on your assumptions, no recommendation.

• Credit & repayment

  Loan refinancing calculator

  See whether refinancing a loan pays off: total cost of the old and the new loan, the saving after switching costs and the break-even point — neutral, no providers.

• Everyday & work

  Hourly wage calculator

  Convert a gross monthly or annual salary to an hourly rate — and back (52 weeks/year) — plus how many working hours a purchase costs. Gross only, no tax.

• Credit & repayment

  Overdraft interest calculator

  Work out the daily interest an overdraft costs — for a period, per month and per year (actual/365) — plus a comparison with a rate you choose, in your browser.

• Credit & repayment

  Effective interest rate calculator

  Find a loan's effective annual rate from its payments and fees as the internal rate of return, or convert a nominal rate to the effective one — in your browser.

• Cars & mobility

  Lease vs buy calculator

  Compare the total cost of leasing and buying a car over the same period — deposit, payments, fees, excess mileage, financing and resale value. Neutral, not advice.

• Property & housing

  Rent-burden calculator

  Work out your rent-to-income share from rent and net income — warm or cold rent — and the rent a target share you set yourself would allow. In your browser.

• Property & housing

  Home purchase budget calculator

  From a monthly loan payment, deposit, interest rate, term and ancillary-cost rate, work out the model loan and modelled maximum purchase price — in your browser.

• Credit & repayment

  Credit Card Payoff Calculator

  Pay off one credit card balance at a fixed rate: compare a fixed monthly payment or a percentage with a minimum — months to clear, total interest and the final payment.

• Property & housing

  Rental yield calculator

  Work out the gross and net rental yield and the gross rent multiplier of a buy-to-let from price, rent, vacancy and costs — unlevered, in your browser.

• Everyday & work

  Real wage calculator

  See what a pay rise is really worth after inflation: enter your gross wage, the nominal change and your own inflation rate for the real change in per cent and money.

• Budget & reserves

  Net-worth calculator

  Enter your assets and debts as line items and see your net worth, the split by category and the debt-to-asset ratio — in your browser, with nothing stored.

• Budget & reserves

  Subscription & fixed-cost calculator

  Convert subscriptions and fixed costs at any payment interval to monthly and yearly totals — with the largest cost driver and an optional invest-instead scenario.

• Everyday & work

  Shared expense split calculator

  Split one shared monthly expense between 2 to 6 people — equally, in proportion to income, or by custom percentages. Each person's share in money and per cent.

• Everyday & work

  Shrinkflation Calculator

  Compare a product's old and new pack: unit price per kg, l or piece, plus package, sticker-price and effective unit-price change. Runs in your browser.

• Property & housing

  Heat Pump Cost Calculator

  Compare heat pump electricity use and running costs with gas or oil heating. Enter annual fuel use, SPF and electricity price to find your break-even point.

• Everyday & work

  Balcony Solar Payback Calculator

  Estimate how many years a plug-in balcony solar system in Germany takes to pay off, from cost, grant, year-one generation, self-consumption and price per kWh.

• Everyday & work

  Gym Membership Cost Calculator

  Compare two or three gym memberships over the same period: comparison cost, what is actually charged, cost per visit and break-even against paying per visit.

• Everyday & work

  Supplement Cost Comparison Calculator

  Compare 2 to 4 supplements by price per gram of declared protein or per reference amount of one ingredient. A price tool only, with no dosage or health claims.

• Property & housing

  Contractor Quote Comparison Calculator

  Compare two or three contractor quotes for the same job on a like-for-like basis: fixed price, time-and-materials and estimate side by side, with a break-even point.

• Everyday & work

  Phone Contract vs SIM-Only Calculator

  Compare what a phone on contract, a handset bought outright with a SIM-only plan, or keeping your current phone really cost over 12, 24 or 36 months.

• Budget & reserves

  Pet Ownership Cost Calculator

  Work out what a pet really costs from your own figures: the first year, a later year, your chosen period and a monthly average — plus a separate emergency reserve.

• Drawdown & planning

  Germany Altersvorsorgedepot Calculator

  Estimate the 2027 state allowances for Germany's Altersvorsorgedepot — basic allowance, child allowance and starter bonus — plus a savings scenario you choose.

• Everyday & work

  Germany Sugar Tax Calculator (2027 Proposal)

  Model what Germany's proposed sugary drinks tax (draft, 14 October 2026) could mean per pack, week, month and year for the drinks you buy. A hypothetical draft, not law.

• Everyday & work

  Coffee Machine Cost Calculator

  Compare pod, bean-to-cup and filter coffee over 1 to 10 years: total cost, cost per cup, purchase price versus running costs, replacement purchases and break-even.

Browse all calculators – the portal grows step by step with further tested calculators.

Why you can trust the results

Every calculator is based on an independently tested calculation function: at least five automated tests, edge-case tests and control calculations against independently derived reference values. Assumptions and limits are shown visibly on every calculator page – and where numbers are examples, they are explicitly marked as an example assumption. Your inputs stay in your browser, without an account and without tracking.