Climate & Atmosphere
Calculators & Tools
Air Quality Index (AQI) Calculator
The Air Quality Index (AQI) Calculator converts measured atmospheric pollutant concentrations into EPA AQI sub-index values using official 2024 breakpoint tables and the piecewise linear interpolation formula mandated by the US Clean Air Act. It operates in two modes: Single Pollutant mode accepts a concentration for any of eight pollutant-averaging-period combinations -- PM2.5 (24-hour, μg/m³), PM10 (24-hour, μg/m³), ozone 8-hour (ppm), ozone 1-hour (ppm), carbon monoxide 8-hour (ppm), sulfur dioxide 1-hour (ppb), sulfur dioxide 24-hour (ppb), and nitrogen dioxide 1-hour (ppb) -- and returns the AQI sub-index, the six-category colour-coded classification (Good through Hazardous), health guidance for sensitive groups and the general public, and a step-by-step formula display substituting the actual breakpoint values used. All Pollutants mode accepts simultaneous inputs for six core pollutants, calculates each sub-index, and reports the overall AQI as the maximum sub-index with the dominant pollutant highlighted in a per-row table. Four presets (clean mountain air, typical city, rush hour, wildfire smoke) populate all six fields for instant demonstration of the contrast between clean and hazardous conditions.
Apparent Temperature Calculator
The Apparent Temperature Calculator computes the human-perceived "feels like" temperature by applying four standard thermal comfort indices to any combination of air temperature, relative humidity, wind speed, and solar radiation. It displays all four indices simultaneously in a comparison table: NWS Wind Chill (2001, used when T ≤ 10°C and wind > 4.8 km/h), NWS Heat Index / Rothfusz regression (used when T ≥ 27°C and RH ≥ 40%), Humidex (Canadian dew-point-based index, valid above 20°C), and the Australian BOM Steadman (1994) apparent temperature formula (AT = Ta + 0.348e − 0.70ws + 0.70Q/(ws+10) − 4.25), which is the only index that incorporates solar radiation. The calculator automatically highlights the recommended index for the entered conditions and shows a step-by-step BOM formula breakdown substituting actual computed values including water vapour pressure. Inputs accept °C or °F, and km/h, mph, or m/s for wind speed; solar radiation uses W/m² with five labelled presets (indoors/night, heavy overcast, partly cloudy, full sun in light clothing, full sun in dark clothing). Six weather scenario presets cover the full range from winter blizzard to tropical swelter. The result card shows a risk classification with colour coding across 10 danger levels from extreme cold to extreme heat, plus a clothing recommendation for the computed apparent temperature.
Atmospheric Pressure Calculator
The Atmospheric Pressure Calculator converts between altitude and atmospheric pressure bidirectionally using the International Standard Atmosphere (ISA) multi-layer barometric model: in the troposphere (0-11,000 m) it applies P = 1013.25 * (1 - 0.0065h/288.15)^5.2561; in the lower stratosphere (11,000-20,000 m) it uses the isothermal exponential P = 226.32 * exp(-0.0001577*(h-11000)). Altitude input accepts metres or feet; pressure output simultaneously shows all seven common units: hPa, Pa, kPa, mmHg, inHg, psi, and atm. Derived quantities include: oxygen partial pressure (pO2 = P * 0.2095) as both an absolute value and percentage of sea-level O2; ISA standard air temperature at the entered altitude; air density (kg/m3) via ideal gas law; and water boiling point in both Celsius and Fahrenheit via the Clausius-Clapeyron equation. An altitude sickness risk panel classifies the entered altitude into five tiers from Low AMS risk (below 2,500 m) through Death Zone (above 8,000 m) with specific acclimatisation guidance. Eight famous-altitude presets cover sea level, Denver, Mexico City, La Paz, aircraft cabin pressurisation equivalent, Everest Base Camp, K2 summit, and Everest summit. A step-by-step formula breakdown shows which ISA layer applies and substitutes actual values into the barometric formula.