Calculators

These are the sums people do on a phone, badly, in a notes app: what a percentage of something is, how old somebody is in years and months, what a monthly loan payment actually comes to once interest is included, and where a height and weight land on the BMI chart.

They run entirely in the page, so nothing you type is sent anywhere — which is the point for the ones that involve money or health. There is no sign-up, no limit on how many times you can use them, and no history kept between visits.

Two of them are worth reading carefully rather than glancing at. A loan payment depends on the compounding period as much as the rate, so a figure quoted per year and a figure quoted per month are not comparable until you say so. And BMI uses one formula for everyone but is read against different charts by sex and age — the tool shows the band rather than only the number, because the number alone has misled a lot of people.