[Form Validation]

// JavaScript Document
$(document).ready(function(){

//declare variables
    function calculate(){
    var weight, height, bmi;
    weight= $('#weight').val();
    height= $('#height').val();
    
  //calculate total
  bmi = weight*703/(height*height);
  bmi = bmi.toFixed(1);
 
  $('#bmi').val(bmi);
 
 
 
 
   if (bmi < 18.5){
     $('#bmi_message').html('Your BMI shows you are under weight.');
  }
 
  if (bmi >= 18.5 && bmi <= 24.9){
      $('#bmi_message').html('Your BMI shows you are a normal weight.');
  }
  if (bmi >= 25 && bmi <= 29.9){
      $('#bmi_message').html('Your BMI shows you are over weight.');
  }
   
     if (bmi > 30){
    $('#bmi_message').html('Your BMI show you are obese.');
  }
 


return false;

}//end of calculate function

    $('#bmiform').submit(calculate);
    $('#bmiform').validate({
        rules: {
        },
        messages:{
        height: "Please enter a valid height between 24 in. and 100 in.", weight: "Please enter a valid weight between 20 lb. and 500 1b."
    }
    
    });
    return false;
    
    
});


I am trying to get this so that it does not calculate unless the form is validated.  Not sure what I am doing wrong.