Math calculators

The percentage page answers three different questions, and they do not feed each other. Percent of a number, what percent one number is of another, and percent change from an old value to a new one. A drop from 90 to 72 is a 20 percent decrease. The climb from 72 back to 90 is a 25 percent increase, because the base changed. Undoing a percent means dividing by what remains, not subtracting the same percent.

The unit converter uses exact definitions. One foot is 0.3048 metres. One pound is 0.45359237 kilograms. Temperature is not a ratio: 72 °F is 22.22 °C. Recipe cups and currency are not on that page. The word counter splits on spaces, counts characters, and estimates reading time at 200 words a minute. The text stays in the browser tab. It is not a grammar checker and it does not store a draft.