Implementing a simple unit converter

Question

I'm new to Angular so please excuse my neewbie questions :) I'm creating a small project to show some sport trainings data. I need to implement a simple converter for units like speed, distance etc. For now, i have created a Pipe that calculates the values and adds the correct unit. I've declared variables to determine which units to use. It looks something like this:

let speedUnit = 'kmh';

switch (args) {
  case 'speed': {
    if (speedUnit == 'kmh') {

      newValue = value * 3.6;
      newValue = newValue.toFixed(2);
      newValue += ' km/h';
    }
    if (speedUnit == 'mph') {
      newValue = value * 2.23694;
      newValue = newValue.toFixed(2);
      newValue += ' mph';
    }
    break;
  }

It works great so far. The problem is, I need it more dynamic, so i can switch the unit with a click. E.g. there's would be a switch in frontend with mph/kmh on it and on click it would change the value of the speedUnit variable from 'kmh' to 'mph' and update the on-screen data.

What would be the best approach here? Using some kind of Service? Observables? As I mentioned, im new to Angular and I'm not yet familiar with all of it's components. :)

Thank's for any help.