Units & Calculators

Two related jobs live in this section: converting a value between units, and working out a number you need — health figures, percentages and other everyday maths. Every tool runs entirely in your browser and shows the formula it used, so the answer can be checked instead of trusted blindly.

What you can do here

• Unit conversion — length, weight, temperature, area, volume and speed, in metric, imperial and common everyday units, with the exact conversion factor shown.
• BMI (body mass index) from height and weight in metric or imperial units, with the WHO and Asian category bands, your healthy weight range, an ideal-weight reference, and a waist-to-height check.
• Percentages — what is X% of Y, X as a percentage of Y, percentage increase and decrease, percentage difference, and discounts.
• More converters and calculators are added to this hub over time.

Why convert or calculate online?

No app to install, no account to create, and no data leaving your device: the arithmetic runs in JavaScript on your own machine, which matters when the numbers describe your body or your money. Results update as you type, and each tool spells out its formula and unit definitions.

Frequently asked questions

• Are these tools free? Yes, all of them, with no sign-up.
• Do you store what I type? No. Inputs stay in your browser and are never sent to a server.
• Are the formulas standard? Yes — BMI uses the WHO formula (kg ÷ m²) with both WHO and Chinese cut-off points available, and unit conversions use the standard factors listed next to each field.
• Can I use the results commercially? Yes, there is no restriction on the numbers you calculate here.