Depending on how much math you do, I prefer custom calculation scripts in Acrobat. I like to set my script to be blank if zero, so the end user can print it out and do it by hand if they want. I’ve also found that sometimes a standard calculation does not auto update, but the script does. Below is an example:

//variable values
var qt1 = +getField(“qty1”).value;
var qt2 = +getField(“qty2”).value;
var qt3 = +getField(“qty3”).value;
var qt4 = +getField(“qty4”).value;
var qt5 = +getField(“qty5”).value;
var qt6 = +getField(“qty6”).value;
var qt7 = +getField(“qty7”).value;
var qt8 = +getField(“qty8”).value;
var qt9 = +getField(“qty9”).value;
var qt10 = +getField(“qty10”).value;
var qt11 = +getField(“qty11”).value;
var qt12 = +getField(“qty12”).value;
var qt13 = +getField(“qty13”).value;
var qt14 = +getField(“qty14”).value;
var qt15 = +getField(“qty15”).value;
var qt16 = +getField(“qty16”).value;
var qt17 = +getField(“qty17”).value;
var qt18 = +getField(“qty18”).value;
var qt19 = +getField(“qty19”).value;
var qt20 = +getField(“qty20”).value;
var pr1 = +getField(“price1”).value;
var pr2 = +getField(“price2”).value;
var pr3 = +getField(“price3”).value;
var pr4 = +getField(“price4”).value;
var pr5 = +getField(“price5”).value;
var pr6 = +getField(“price6”).value;
var pr7 = +getField(“price7”).value;
var pr8 = +getField(“price8”).value;
var pr9 = +getField(“price9”).value;
var pr10 = +getField(“price10”).value;
var pr11 = +getField(“price11”).value;
var pr12 = +getField(“price12”).value;
var pr13 = +getField(“price13”).value;
var pr14 = +getField(“price14”).value;
var pr15 = +getField(“price15”).value;
var pr16 = +getField(“price16”).value;
var pr17 = +getField(“price17”).value;
var pr18 = +getField(“price18”).value;
var pr19 = +getField(“price19”).value;
var pr20 = +getField(“price20”).value;

//multiplication
var tt1 = qt1 * pr1;
var tt2 = qt2 * pr2;
var tt3 = qt3 * pr3;
var tt4 = qt4 * pr4;
var tt5 = qt5 * pr5;
var tt6 = qt6 * pr6;
var tt7 = qt7 * pr7;
var tt8 = qt8 * pr8;
var tt9 = qt9 * pr9;
var tt10 = qt10 * pr10;
var tt11 = qt11 * pr11;
var tt12 = qt12 * pr12;
var tt13 = qt13 * pr13;
var tt14 = qt14 * pr14;
var tt15 = qt15 * pr15;
var tt16 = qt16 * pr16;
var tt17 = qt17 * pr17;
var tt18 = qt18 * pr18;
var tt19 = qt19 * pr19;
var tt20 = qt20 * pr20;

//addition
var subtotal = tt1 + tt2 + tt3 + tt4 + tt5 + tt6 + tt7 + tt8 + tt9 + tt10 + tt11 + tt12 + tt13 + tt14 + tt15 + tt16 + tt17 + tt18 + tt19 + tt20;

// Display result if not zero
if (subtotal !== 0) {

event.value = subtotal;

} else {

event.value = “”;
}