Enter the known numbers in the correct boxes then click in the remaining empty box and your result will compute.

Heat Index Calculator
(See formula below)
Temperature ºF
Humidity %
Heat Index ºF
The temperature must be above 56ºF.

 Temperature Calculator
(See formula below)
Fahrenheit ºF
Celsius ºC

Wind Chill Calculator
(See formula below)
Wind speed mph
Temperature ºF
Wind Chill ºF

Relative Humidity Calculator
(See formula below)
Temperature ºF
Dewpoint ºF
Relative Humidity %

Calculator Formulas

Heat index is based on the formula:

HI = -42.379 + (2.04901523 x T + 10.14333127 x RH) - (0.22475541 x T x RH) - (.00683783 x T2) - (.05481717 x RH2) + (.00122874 x T2 x RH) + (.00085282 x T x RH2) - (.00000199 x T2 x RH2)

T is the temperature in Fahrenheit, RH is the relative humidity.

To convert from Celsius to Fahrenheit:

F = (C x 9/5) + 32
C = 5/9 x (F-32)

C is the temperature in Celsius, F is the temperature in Fahrenheit.

To calculate wind chill:

WC = 35.74 + 0.6215T - 35.75 (V 0.16) + 0.4275T (V 0.16)

V is the wind speed, T is the temperature in Fahrenheit.

To calculate indoor humidity, enter room temperature (usually 72 ºF) but use the outdoor dewpoint.

To calculate relative humidity, first convert the temperature into Celsius using this equation: C = 5/9 x (F-32).

Then use the equation to determine relative humidity:

RH = (6.11*10^((7.5*D)/(237.7+D)))/(6.11 * 10^((7.5*T)/(237.7+T)))

T is the temperature in Celsius, D is the dewpoint temperature in Fahrenheit
10^4 is 10 to the fourth power. / is divide.