Calculators and tools for money, home, energy, security, the web, AI and coding
Free calculators and tools, with no sign-up and no email. Plan your budget and savings, weigh an investment, a mortgage, solar panels or a heat pump, make a strong password, check a web page for search engines, watch a neural network recognise a digit, or learn the basics of coding with a robot and blocks. Each tool explains how it calculates and where its data come from.
Calculators and tools
- Budget and savingBudget CalculatorEnter your income and expenses, monthly or yearly, and see what is left over in a month and a year, where the money goes and how big an emergency fund you need.
- Budget and savingSubscription CalculatorAdd up streaming, apps, the gym and every other subscription: what you pay a month and a year, what cancelling some would save and what that money could grow to.
- Budget and savingSavings Goal CalculatorEnter your goal, what you have saved, your income and expenses: see how many months it takes, or how much to put aside each month to get there in time.
- InvestingCompound Interest CalculatorSee how your savings grow with compound interest and regular monthly contributions: final balance, interest earned and a year-by-year breakdown.
- InvestingDCA CalculatorSee how much regular monthly investing in the S&P 500, global ETFs, stocks, gold or bitcoin would be worth today, compared with investing everything at once.
- InvestingFIRE CalculatorSee when you can reach financial independence: your FIRE number, the age you can stop working, Coast and Barista FIRE, and how often the money would have lasted in every retirement since 1928.
- InvestingInflation calculatorSee what an amount from any year is worth today and how much buying power it lost, from official consumer price data. Plus a look into the future, savings against inflation, and 17 countries compared.
- InvestingFund fee calculatorCompare two funds with different yearly and entry fees: what you end up with, what the fees cost in money and how much more the expensive fund would have to earn to be worth it.
- InvestingBorrow-to-Invest CalculatorSee what investing a loan in bitcoin, the S&P 500 or stocks would have earned or lost, the return you need to cover the interest and how far the investment can fall below the debt.
- Home and loansMortgage CalculatorCalculate your monthly mortgage payment and total interest, see what happens after the fixed-rate period, how much extra payments save and which offer is cheaper.
- Home and loansRental Property CalculatorBuying a property to let with a mortgage? See the monthly cash flow, the rental yield, when the rent covers everything and when a sale would leave you in profit. Price history by city.
- Home and loansRent vs Buy CalculatorCompare buying a home with a mortgage against renting and investing the difference: who ends up with more, after how many years buying pays off, and the rent at which both come out the same.
- EnergySolar Panel Payback CalculatorWork out how many years your solar panels take to pay back and whether they pay off at all: how much power you use yourself, how much you sell to the grid and what a battery adds.
- EnergyHeat Pump Payback CalculatorWork out how many years a heat pump takes to pay back against your gas, oil, propane, electric, coal or wood heating, what it costs to run and whether it pays off at all.
- EnergyElectric vs Gas Car CalculatorSee how much less an electric car costs to run than a petrol or diesel one a month, a year and per mile: charging against fuel, maintenance, insurance and tax, plus the total cost with buying and selling, and the CO₂.
- SecurityPassword generatorGenerate a strong random password in your browser. Choose the length and characters, and see how strong it is and how long it would take to guess. Nothing is sent or saved.
- SecurityPassphrase generatorMake a strong passphrase of random words right in your browser. Pick the number of words and see how strong it is and how long it would take to guess. Nothing is sent or stored.
- Websites and SEOSEO checkerFree SEO test of a web page: indexing, robots.txt, sitemap, canonical, title, meta description, headings, images, links, hreflang, structured data and speed from Google, with how to fix each problem.
- How AI worksHow a neural network recognises digitsDraw a digit from 0 to 9 and watch a small neural network recognise it: which neurons light up, what each one looks for and how the answer is worked out, step by step.
- CodingCoding for beginners: a robot and blocksLearn the logic of coding: snap a program together from blocks, watch a robot run it step by step on a grid and see the same code in Python. Free, no sign-up.
Latest articles
All articles- Data
How much electricity does a heat pump use? By month and by year
How many kWh of electricity a heat pump uses in a family house month by month, what it costs, why winter takes the most, how house size matters and how much less it uses with underfloor heating.
- Guide
How a neural network recognises a digit, step by step
We follow a handwritten digit through a real neural network: what it sees, how a neuron adds up, how the network learned its weights and which digits it mixes up most.
- Comparison
Heat pump or gas furnace: when does a heat pump pay off?
When a heat pump saves against gas heating, why the electricity-to-gas price ratio and the COP decide, and how it works out in the US and 8 European countries.