Datatype for floating-point numbers, a number that has a decimal point. Floating-point numbers are often used to approximate analog and continuous values because they have greater resolution than integers. Floating-point numbers can be as large as 3.4028235E+38 and as low as -3.4028235E+38. They are stored as 32 bits (4 bytes) of information.

Floats have only 6 decimal digits of precision. That means the total number of digits, not the number to the right of the decimal point. On the 86Duino, you can get more precision by using a double (e.g. up to 15 digits), and there is an FPU (Floating Point Unit) integrated in the CPU to accelerate the computation of floating-point numbers.

Floating point numbers are not exact, and may yield strange results when compared. For example 6.0 / 3.0 may not equal 2.0. You should instead check that the absolute value of the difference between the numbers is less than some small number.

Floating point math is also much slower than integer math in performing calculations, so should be avoided if, for example, a loop has to run at top speed for a critical timing function. Programmers often go to some lengths to convert floating point calculations to integer math to increase speed.

If doing math with floats, you need to add a decimal point, otherwise it will be treated as an int. See the Floating point constants page for details.


float myfloat;
float sensorCalbrate = 1.117;


float var = val;

var – your float variable name
val – the value you assign to that variable

Example Code

   int x;
   int y;
   float z;

   x = 1;
   y = x / 2;            // y now contains 0, ints can't hold fractions
   z = (float)x / 2.0;   // z now contains .5 (you have to use 2.0, not 2)

See also

Variable Declaration

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The text of the 86Duino reference is a modification of the Arduino reference, and is licensed under a Creative Commons Attribution-ShareAlike 3.0 License. Code samples in the reference are released into the public domain.