How to convert decimal string to float?

[Joe Shmoo]

I have a string representing a decimal value like 123.456 (or -90.4005 etc.) and I need to represent it by a float datatype (4 bytes). What is the math used to do so? When I Google all I can find are calculators that do it for you but I have to implement it on a microcontroller . Thanks.

[weaknessforcats]

Are you using C or C++?

If it's C, then call atof().

If it's C++, insert your string into a stringstream and extract it to a double.