EditText edtVao = (EditText) findViewById(R.id.vao);
    final int edtVaoNum = Integer.parseInt(edtVao.getText().toString());

    // Spinner
    Spinner spnCargas = (Spinner) findViewById(R.id.spn_cargas);
    ArrayAdapter<CharSequence> spnAdapter = ArrayAdapter.createFromResource(this, R.array.str_cargas, R.layout.spinner_style);
    spnAdapter.setDropDownViewResource(R.layout.spinner_dropdown_style);
    spnCargas.setAdapter(spnAdapter);
    // Spinner

    spnCargas.setOnItemSelectedListener(
            new AdapterView.OnItemSelectedListener() {

                public void onItemSelected(AdapterView<?> spnAdpView, View v, int carga, long id) {

                    int porcentagem;

                    if(spnAdpView.getItemAtPosition(carga).toString() == "Cargas pequenas"){ porcentagem = 4; }
                    else if(spnAdpView.getItemAtPosition(carga).toString() == "Cargas médias"){ porcentagem = 5; }
                    else { porcentagem = 6;}

                }// fecha onItemSelected

                public void onNothingSelected(AdapterView<?> arg0){}
            }//fecha OnItemSelectedListener
    ); // fecha setOnItemSelectedListener

    int r = edtVaoNum * porcentagem / 100;