Calculating a percent value reverts to 0

Question

My goal is to calculate a 2% interest rate against a loan denominated in DAI.

uint256 loanAmount = 500 * 10 ** 18 // $500 in USD

function calculateInterest( uint256 _loanAmount) public view returns (uint256) {
       return 2 / _loanAmount;
    }

However, when I execute the function, the value i get is 0

Any idea what I'm doing wrong?

Answer 1

Math in Solidity is done entirely using fixed-point numbers.

You can calculate the interest amount as followed:

uint256 private interestPercentage  = 2;
function calculateInterest( uint256 _loanAmount) public view returns (uint256) {
   return _loanAmount * (100 + interestPercentage) / 100 - _loanAmount;
}