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ESP Easy can use a simple formula to change the sensor value before it is send to the Home Automation controller. (In most cases this is not needed and in most cases this can also be accomplished within the Home Automation software)

A few samples will be provided here. Remember that this is just a simple build-in 'calculator' with only the basic stuff like add, substract, multiply, devide.

When the sensorvalue has been read from the device, it is parsed through the formula function. The value is addressed as this:


So if you like to add a constant value of '2' to the sensorvalue, you would enter:


If you count in liters and need the value in cubic meters:


The same syntax can also be used in rules.

Arithmetic operations

You can use the following operations in formulas and rules:

If %value% is 10 and the formula is %value%<operation>2

  • Addition (+): 10+2=12
  • Subtraction (−): 10-2=8
  • Multiplication (*): 10*2=20
  • Division (/): 10/2=5
  • Exponent (^): 10^2=100

Square root etc.

Just for information, the square root can be exchanged for %value%^0.5 and cube root for %value%^0.3333.


You can convert integers and floats into human readable information using these commands. These are not working in formulas since the output is a string and not a true float value. The intended use is in rules (Publish command as an example) and displays etc.

From >>> To Type Syntax Example
Deg >>> Bearing bearing/wind direction  %c_w_dir%([TaskName#ValueName]) %c_w_dir%(45)=NE (-359 to +360 is allowed)
C >>> F Celsius to Fahrenheit  %c_c2f%([TaskName#ValueName]) %c_c2f%(32.0)=89.6
m/s >>> Beaufort wind speed/gust to Beaufort scale  %c_ms2Bft%([TaskName#ValueName]) %c_ms2Bft%(23.3)=9
cm >>> ' " centimeter to imperial (feet) + inches  %c_cm2imp%([TaskName#ValueName]) %c_cm2imp%(200.2)=5' 6.7"
mm >>> ' " millimeter to imperial (feet) + inches  %c_mm2imp%([TaskName#ValueName]) %c_mm2imp%(200.0)=7.87"
%c_mm2imp%(12200)=20' 0.3"
min >>> day minutes to days  %c_m2day%(%uptime%) %c_m2day%(7860)=4.46
min >>> day hour minutes to days + hours  %c_m2dh%(%uptime%) %c_m2dh%(7860)=4d 11h
min >>> day hour min minutes to days + hours + minutes  %c_m2dhm%(%uptime%) %c_m2dhm%(3642)=2d 12h 42m
sec >>> day hour min sec seconds to days + hours + minutes + seconds  %c_s2dhms%([TaskName#ValueName]) %c_s2dhms%(1234567890)=14d 6h 56m 8s