function calc(form) {
//  ersätt felaktig inmatning av komma-separator
	komma = ","; punkt = "."; temp = "" + form.crSpeed.value; 
	while (temp.indexOf(komma)>-1) {
		pos= temp.indexOf(komma);
		temp = "" + (temp.substring(0, pos) + punkt + temp.substring((pos + komma.length), temp.length));
		}
	form.crSpeed.value = temp;
	
	if (form.units(0).checked) { var metrics = 1; } else { var metrics = 0; }

	if (form.crSpeed.value.length==0||form.noStrFWD.value.length==0||form.stpLFWD.value.length==0) {
		alert("Please enter some parameters in order to calculate production!"); 
		document.prod.crSpeed.focus();
	} else {
		if (form.noStrBKWD.value.length==0||form.noStrBKWD.value==0||form.noStrBKWD.value=="") { 
			form.noStrBKWD.value=0; 
			form.stpLBKWD.value=0; 
		} else {
			if (form.stpLBKWD.value==0) { form.stpLBKWD.value=Math.round(form.stpLFWD.value/2); 
		}
	}

	var pM2=Math.round(100*((((form.crSpeed.value)/(form.noStrFWD.value+form.noStrBKWD.value))*((form.stpLFWD.value-form.stpLBKWD.value)/1000))*60))/10;
	if (metrics) { prod.productionM2.value=pM2 + " m²/hr"; }
	else { var feet2temp = Math.round(100*(pM2*1.07640))/10; prod.productionM2.value=feet2temp + " ft²/hr"; }
 
	if (form.depth.value!=0) 
		{ var volTemp=Math.round(100*(pM2*(form.depth.value/1000)))/100;
		if (metrics) 
			{ prod.productionM3.value=volTemp + " m³/hr"; }
  		else 
			{ prod.productionM3.value=Math.round(100*(volTemp*3.53160))/10 + " ft³/hr"; 
		}
	}
	else 
 		{ prod.productionM3.value=""; 
	}
 
	if (form.osc.value!=0) {
		if (form.oscWidth.value==0) { form.oscWidth.value=100;}
			var jetSp=((((form.oscWidth.value*2)/1000)*form.osc.value)+(form.crSpeed.value/1000))/60;
			form.jetSpeed.value=Math.round(1000*jetSp)/1000;
			form.jetSpeed.value=form.jetSpeed.value+" m/sec.";
			form.period.value=Math.round(100*((form.crSpeed.value*10)/form.osc.value))*100/100+" mm";
		} else { 
			form.jetSpeed.value="";
	  		form.period.value="";
		}
	}
  
}