Weather and Climate

  • Pressure Altitude Calculator
    Calculate pressure altitude from field elevation and altimeter setting (inHg) using the standard 29.92 reference. Fast, accurate aviation tool for pilots.
  • Knots to MPH Wind Speed Converter
    Convert wind speed from knots to mph, km/h, and m/s instantly. Free, accurate knots-to-mph converter for sailing, aviation, and weather.
  • CADR & Room Size Calculator
    Find the maximum room size an air purifier can handle from its CADR rating. Calculate floor area in sq ft for any target air changes per hour (ACH).
  • Boiling Point Altitude Calculator
    Find the boiling point of water at any altitude in °C and °F, plus atmospheric pressure. Free, instant boiling point altitude calculator.
  • Coriolis Force Calculator
    Calculate the Coriolis force on a moving mass on Earth from mass, velocity and latitude using Fc = 2mvΩsin(φ), with Ω = 7.292e-5 rad/s.
  • Dry Adiabatic Lapse Rate Temperature Calculator
    Calculate how air temperature changes with altitude using the dry adiabatic lapse rate of 9.8 °C per 1000 m. Enter surface temperature and altitudes.
  • Hurricane Category Calculator (Saffir-Simpson)
    Find the Saffir-Simpson hurricane category from sustained wind speed in mph, knots or km/h. Instantly classify Category 1-5 storms.
  • Snow Water Equivalent (SWE) Calculator
    Calculate snow water equivalent (SWE) from snow depth and density. Get SWE in cm, mm and inches of water plus the snow-to-water ratio instantly.
  • Saturation Vapor Pressure Calculator
    Calculate saturation vapor pressure from air temperature using the Tetens equation. Get results in kPa, hPa (mbar), and Pa instantly.
  • UV Index Sunburn Time Calculator
    Estimate how long until sunburn from the UV Index, your SPF sunscreen, and skin type. Quick, free sun-safety exposure-time calculator.
  • Heating Degree Days (HDD) Calculator
    Calculate Heating Degree Days (HDD) from your daily high, low and base temperature. Estimate heating demand using HDD = max(0, Tbase − mean temp).
  • Cooling Degree Days (CDD) Calculator
    Calculate cooling degree days (CDD) from daily high and low temperatures and a base temperature. Estimate building cooling energy demand fast.
  • Wet Bulb Globe Temperature (WBGT) Calculator
    Calculate outdoor Wet Bulb Globe Temperature (WBGT) from wet-bulb, globe, and air temperatures using WBGT = 0.7·Tw + 0.2·Tg + 0.1·Ta. Result in °C and °F.
  • Wind Pressure Calculator
    Calculate wind pressure (psf and Pa) and total force on walls, signs, and surfaces from wind speed using P = 0.00256 × v² and dynamic pressure.
  • Growing Degree Days (GDD) Calculator
    Calculate daily Growing Degree Days (GDD) from max, min, and base temperatures to track crop and pest development heat accumulation.
  • Vapor Pressure Deficit (VPD) Calculator
    Calculate Vapor Pressure Deficit (VPD) in kPa from air temperature and relative humidity. Free grow-room and greenhouse VPD tool with SVP and AVP.
  • Specific Humidity Calculator
    Calculate specific humidity from water vapor pressure and total air pressure using q = 0.622e/(p - 0.378e). Get results in g/kg and kg/kg instantly.
  • Frost Point Calculator
    Calculate the frost point temperature from air temperature and relative humidity using the Magnus formula for saturation over ice (below freezing).
  • Fahrenheit to Kelvin Calculator
    Convert Fahrenheit to Kelvin instantly with K = (F + 459.67) x 5/9. Shows step-by-step working and flags non-physical values below absolute zero.
  • Temperature Conversion Calculator
    Convert temperature between Celsius, Fahrenheit, Kelvin, Rankine and Reaumur. Pick any two scales, enter a value, and see the exact converted result with steps.
  • Kelvin to Fahrenheit Converter
    Convert Kelvin (K) to Fahrenheit (°F) instantly with step-by-step working. Uses °F = K × 9/5 − 459.67. Free, accurate temperature converter.
  • Kelvin to Rankine Converter
    Convert Kelvin (K) to Rankine (°R) instantly. Uses °R = K × 9/5 with full conversion steps, reference points, and a worked example.
  • Fahrenheit to Celsius Converter
    Convert temperatures between Fahrenheit and Celsius in both directions. Free °F to °C and °C to °F converter with formula and worked solution steps.
  • Kelvin to Celsius Converter
    Convert Kelvin (K) to degrees Celsius (°C) instantly. Enter a temperature in Kelvin and see the result plus a step-by-step worked solution.

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