public class MouseDeltaCheck : MonoBehaviour
{
    public Vector2 screenPos;
    public Vector2 positionDelta;
    public Vector2 inputDelta;
    public Vector2 ratio;

    void Update() {
        Vector2 newScreenPos = Input.mousePosition;

        positionDelta = newScreenPos - screenPos;

        inputDelta = new Vector2(Input.GetAxis("Mouse X"), Input.GetAxis("Mouse Y"));

        if(inputDelta.x != 0f)
            ratio.x = positionDelta.x / inputDelta.x;
        if (inputDelta.y != 0f)
            ratio.y = positionDelta.y / inputDelta.y;

        screenPos = newScreenPos;
    }
}

{Change in Pixel Position} * {Axis Sensitivity} * {OS Scaling Factor} * 2