Apparent Temperature Calculator
Work out how hot or cold it really feels using the Australian Bureau of Meteorology's apparent temperature (Steadman) formula. It blends air temperature, humidity and wind into a single shade 'feels-like' figure, so you can judge heat stress or wind chill more realistically than the thermometer alone.
Enter Values
How to use this calculator
- Enter the current air temperature in °C (negative values are allowed for cold conditions).
- Enter the relative humidity as a percentage (0–100) and the wind speed at 10 m in metres per second.
- Read the apparent temperature, the underlying water vapour pressure, and how many degrees warmer or cooler it feels than the actual air temperature.
How it works
The tool uses the BOM/Steadman relation AT = Ta + 0.33·e − 0.70·ws − 4.00, where Ta is air temperature (°C), ws is wind speed (m/s at 10 m) and e is the water vapour pressure in hPa. The vapour pressure e = (RH/100) × 6.105 × exp(17.27·Ta / (237.7 + Ta)) captures how humid the air is. Higher humidity increases e and pushes the apparent temperature up, because moist air slows the evaporation of sweat; wind subtracts from it through the −0.70·ws term. The constant −4.00 calibrates the index to a shaded, ventilated body.
Worked example
Worked example. At 30 °C, 60% relative humidity and 3 m/s wind, the vapour pressure e ≈ 25.37 hPa, so AT = 30 + 0.33×25.37 − 0.70×3 − 4.00 ≈ 32.3 °C — it feels about 2.3 °C warmer than the thermometer reads.
Common mistakes
- Entering wind speed in km/h instead of m/s — divide km/h by 3.6 first (10 m/s ≈ 36 km/h).
- Expecting the 'feels-like' value to match a phone weather app in full sun; this is the shade formula and excludes direct solar radiation, which can add several degrees.
- Typing relative humidity as a fraction (0.6) rather than a percentage (60).
Frequently asked questions
Why does it feel hotter than the air temperature on humid days?
High humidity means sweat evaporates slowly, so your body sheds less heat. The formula reflects this: more moisture raises the water vapour pressure e, which adds to the apparent temperature.
Does this include the effect of direct sunlight?
No. This is the Bureau of Meteorology's shade apparent temperature. Standing in direct sun can feel several degrees hotter again because solar radiation is not part of the equation.
Related tools
- Humidity from Wet & Dry Bulb Calculator
- Frost Risk Temperature Calculator
- Vapour Pressure Deficit (VPD) Calculator
- Air Density Calculator
- Heat Index Calculator
- Wind Chill Calculator
Explore more in Weather & Environmental Monitoring.
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.