Weather and Climate

  • PM2.5 to AQI Calculator (US EPA)
    Convert a PM2.5 concentration (µg/m³) into the US EPA Air Quality Index (AQI) using official piecewise linear interpolation and category breakpoints.
  • Car Trip Carbon Footprint Calculator
    Calculate the CO₂ emissions of a car trip from distance, fuel economy and fuel type. Split the footprint per passenger and see grams of CO₂ per km.
  • Wind Power Density Calculator
    Calculate wind power density in W/m² from air density and wind speed using P/A = 0.5·ρ·v³. Free, fast wind energy resource tool.
  • Dew Point Calculator
    Calculate dew point from air temperature and relative humidity using the Magnus formula. Free, accurate dew point calculator in °C for any climate.
  • P Wave Travel Time Calculator
    Enter epicentral distance (km) and P wave velocity (km/s) to get travel time in seconds, minutes, and hours, plus seismic zone and crust type.
  • Electricity Carbon Footprint Calculator
    Calculate the CO₂ carbon footprint of your electricity use from kWh and your grid emission factor (kg CO₂/kWh), per period and total.
  • Wind Speed at Altitude Calculator
    Estimate wind speed at any height with the wind shear power law v2 = v1·(h2/h1)^α. Scale measured wind to turbine hub height for any terrain.
  • Rainfall Intensity Calculator
    Calculate rainfall intensity in mm/hr from rainfall depth and duration. Free, instant rain intensity calculator with category classification.
  • Heating & Cooling Degree Days Calculator
    Calculate heating (HDD) and cooling (CDD) degree days from daily high/low temperatures and a base temperature. Estimate energy demand over any period.
  • Specific Heat Capacity Calculator
    Calculate specific heat capacity from heat energy, mass and temperature change using c = Q / (m·ΔT). Fast, accurate physics tool with worked example.
  • Final Temperature of Mixing Two Liquids Calculator
    Calculate the final equilibrium temperature when two liquids (such as water) of different masses, specific heats, and temperatures are mixed together.
  • Heat Transfer Rate Calculator
    Calculate heat energy transferred (Q = mcΔT) from mass, specific heat, and temperature change. Free physics calculator with joules and kilojoules output.
  • Wind Direction Degrees to Compass Calculator
    Convert wind direction in degrees (0–360°) to a 16-point compass heading like N, NE, SSW or W instantly with this free calculator.
  • Newton's Law of Cooling Calculator
    Calculate the temperature of a cooling (or warming) object over time with Newton's Law of Cooling and find the thermal time constant τ = 1/k.
  • Clausius–Clapeyron Vapor Pressure Calculator
    Estimate vapor pressure at a new temperature with the Clausius–Clapeyron equation. Enter P1, T1, T2 and ΔHvap to find P2 instantly.
  • Celsius to Fahrenheit Thermostat Calculator
    Convert Celsius to Fahrenheit (and back) instantly. Perfect for setting your thermostat, cooking, and weather. Uses F = C × 9/5 + 32.
  • Fahrenheit to Celsius Travel Converter
    Convert Fahrenheit to Celsius instantly for travel. Enter any °F temperature and get the exact °C value using C = (F − 32) × 5/9.
  • Return Period & Exceedance Probability Calculator
    Calculate the probability that a storm or flood with return period T is exceeded at least once over n years. Free hydrology risk calculator.
  • Fahrenheit to Celsius Fever Calculator
    Convert body temperature between Fahrenheit and Celsius and instantly see whether the reading reaches the 38 °C / 100.4 °F fever threshold.
  • Oven Temperature Conversion Calculator
    Convert oven temperatures between Fahrenheit, Celsius and UK Gas Mark instantly. Enter any value and get all three equivalents for perfect baking.
  • Ideal Gas Law Temperature Calculator
    Solve for temperature using the ideal gas law T = PV/(nR). Enter pressure, volume, and moles to get the gas temperature in K, °C, and °F.
  • Specific Gas Constant Air Density Calculator
    Calculate humid air density from temperature, pressure and relative humidity using the specific gas constants for dry air and water vapor.
  • Rainwater Harvesting Volume Calculator
    Estimate how many gallons of rainwater you can harvest from a roof. Enter catchment area, rainfall in inches, and collection efficiency.
  • Tornado EF Scale Calculator
    Convert a tornado's 3-second gust wind speed into its Enhanced Fujita (EF0–EF5) rating. Enter mph or km/h to instantly find the EF category.

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