The numbers that come up in ordinary life
What a loan really costs. What actually lands in your account. How many grams are in a cup of flour. No account, nothing between you and the answer, and nothing you type leaves your device.
18 calculators, all free
Loans & mortgages
What a loan actually costs, and what paying extra saves.
- Mortgage payment calculatorThe monthly payment on a mortgage, the total interest over its life, and what the payment really is once tax and insurance are in it.
- Car loan calculatorWhat a car costs per month once the down payment and trade-in come off, and what the loan adds over the sticker price.
- Extra payment calculatorWhat paying a bit more each month does to a loan — in interest saved and in years removed from the term.
Worth reading
- Why your lender's quote doesn't match the calculatorA calculator gives you principal and interest. A lender quotes PITI, plus pricing set by your credit file. Here is every line between the two.6 min read
- What paying an extra $100 a month actually doesOverpaying works because of where the money lands, not how much it is. Why the same $100 is worth several times more in year two than year twenty.5 min read
Salary & pay
What lands in your account, not what the offer letter says.
- Take-home pay calculatorAn estimate of what actually reaches your account after federal income tax and FICA, using the published 2026 figures.
- Hourly to salary converterAn hourly rate as a yearly salary and back again, with the hours and weeks you actually work rather than an assumed 40 × 52.
Worth reading
- Where your paycheck actually goesSalary divided by twelve is not your paycheck. What federal brackets and FICA take, and why the state line is the one nobody can compute for you.6 min read
- The 2,080-hour year is a fictionEvery hourly-to-salary conversion assumes 40 × 52. Almost nobody works that year — and the gap runs in both directions.4 min read
Converters
Units and dates, converted exactly.
- Length converterConvert length between every common unit.
- Weight converterConvert weight between every common unit.
- Temperature converterConvert temperature between every common unit.
- Volume converterConvert volume between every common unit.
- Speed converterConvert speed between every common unit.
- Area converterConvert area between every common unit.
- Currency converterConvert between 30 currencies at the European Central Bank's published reference rates, with the date those rates were set.
- Age calculatorAn exact age in years, months and days — handling leap years and short months properly, which is where mental arithmetic goes wrong.
- Days between datesThe exact number of days between two dates, and what those dates fall on.
- Business days calculatorWorking days between two dates, weekends excluded.
Worth reading
- Why your bank's exchange rate is worse than the one you looked upThe rate you look up is the mid-market rate, and nobody sells currency to the public at it. What the spread really costs you.5 min read
- Date maths is harder than it looksCounting days looks trivial until leap years, inclusive counting and public holidays get involved. Where the off-by-one actually comes from.5 min read
Kitchen
Cups to grams, oven temperatures, and scaling a recipe.
- Cups to grams converterCups to grams and back, per ingredient — because a cup of flour and a cup of honey weigh very different amounts.
- Oven temperature converterCelsius, Fahrenheit and gas mark side by side, with the fan-oven reduction — using the settings an oven dial actually has.
- Recipe scalerRescale a whole ingredient list for a different number of servings, with quantities rounded to fractions you can measure.
Worth reading
- A cup of flour is not a weightThe same cup of flour can weigh 120 g or 150 g depending on how it got into the cup. Why volume betrays you, and when it actually matters.5 min read
- Gas mark, fan, and the twenty-degree ruleFan ovens cook hotter than the dial says, gas marks are not linear, and recipes rarely tell you which they mean. How to read any oven instruction.4 min read