Hazard calculators
Free calculators for earthquakes, heat, cold, lightning and hurricanes. Each one shows its formula, a worked example and the agency or paper it comes from, so you can check the answer or use it in a lesson or an article. They work without JavaScript.
- Earthquake magnitude and energy calculator
Compare two magnitudes: how many times more energy and how much larger the waves, and each one's energy in joules and tonnes of TNT.
- Heat index calculator
The National Weather Service heat index from temperature and humidity, in °F or °C, with the NWS caution and danger classes.
- Wet-bulb temperature calculator
Wet-bulb temperature from air temperature and humidity (Stull 2011), and what the research says about the limits of the human body.
- Lightning distance calculator
How far away the lightning was, from the seconds between flash and thunder, and when it is time to go indoors.
- Wind chill calculator
Wind chill from temperature and wind speed in °C or °F (the 2001 NWS formula), with Environment Canada's frostbite risk.
- Hurricane category and Beaufort calculator
Wind speed in km/h, mph, knots or m/s to its Saffir-Simpson category and Beaufort force, from NOAA's own tables.
- Emergency kit checklist builder
A household checklist with quantities of water and food for 3, 7 or 14 days, medicine, documents, children, older people, pets and the hazards where you live, from Ready.gov, the British Red Cross and WHO. Tick items off and print it.
These are estimates for learning and planning. They are not forecasts or warnings and cannot say whether conditions are safe. For decisions, follow your national weather service and local authorities. For what is happening now, see live alerts and the live map.
Questions
Are these calculators official?
No. They use the formulas and tables published by the US National Weather Service, the National Hurricane Center, the USGS, Environment and Climate Change Canada and the peer-reviewed papers named on each page, but the answers are estimates for learning. For decisions, follow your national weather service and local authorities.
Do they work without JavaScript?
Yes. Each calculator is an ordinary form: press Calculate and the page works out the answer. With JavaScript on, the answer updates as you type.