C++: Not recognizing char value when evaulating if statement

I searched for this for a while, and asked my professor, but neither of us are sure exactly what's going on. That likely means it's a typo somewhere, but every time I run this code, for whatever reason, it calls all functions regardless of whether the if statement evaluates to true

int main()
 {
 char StartUnit, EndUnit;
  double StartVal = 0, EndVal = 0;
  double CalcVal = 0;
  static double result = 0;`

 ` //Receive user input`

 ` cout << "Please enter the unit which you would like to convert from: ";
  cin >> StartUnit;
  cout << "What is your initial value?: ";
  cin >> StartVal;
  cout << "Please enter the unit which you would like to convert to: ";
  cin >> EndUnit;

  `//Step 1: Convert input to celsius`

  `if (StartUnit = 'f')
  {
  CalcVal = FarCel(StartVal);
  }`

  `if (StartUnit = 'k')
  {
  CalcVal = KelCel(StartVal);
  }`

  `if (StartUnit = 'r')
  {
  CalcVal = RakCel(StartVal);
  }`

  //Step 2: Conver celsius to desired value

  cout << CalcVal;


  return 0;
}
`

When I output CalcVal, no matter what, it seems to run through all three functions. It doesnt matter what I type, r, c, f, they all evaulate the same. Could I have some advice on where I'm going wrong?

The random quotes scattered were from before I read about CTRL+K