diff -r 6e373acc5d00 -r 0e9a725354ac www/js/rec_edit.js
--- a/www/js/rec_edit.js	Tue Apr 21 17:01:22 2020 +0200
+++ b/www/js/rec_edit.js	Fri Apr 24 14:10:47 2020 +0200
@@ -2534,10 +2534,10 @@
   });
   $('#batch_size').on('change', function(event) {
    console.log('batch_size change:' + event.args.value + ' old:' + dataRecord.batch_size);
-   var factor, new_boil = parseFloat(event.args.value) + dataRecord.boil_size - dataRecord.batch_size;
-   factor = parseFloat(event.args.value) / dataRecord.batch_size;
-   dataRecord.boil_size = new_boil;
-   $('#boil_size').val(Round(new_boil, 2));
+   var evap = (0.1 * parseFloat(event.args.value)) * dataRecord.boil_time / 60;
+   dataRecord.boil_size = parseFloat(event.args.value) + evap;
+   var factor = parseFloat(event.args.value) / dataRecord.batch_size;
+   $('#boil_size').val(Round(dataRecord.boil_size, 2));
    dataRecord.sparge_volume *= factor;
    $('#sparge_volume').val(dataRecord.sparge_volume);
    dataRecord.batch_size = parseFloat(event.args.value);
@@ -2554,14 +2554,11 @@
   });
   $('#boil_time').on('change', function(event) {
    console.log('boil_time change:' + parseFloat(event.args.value) + ' old:' + dataRecord.boil_time);
-   var new_boil, new_evap, old_evap = parseFloat(dataRecord.boil_size) - parseFloat(dataRecord.batch_size);
-   new_evap = old_evap * (parseFloat(event.args.value) / dataRecord.boil_time);
-   new_boil = parseFloat(dataRecord.batch_size) + new_evap;
+   var new_evap = (0.1 * parseFloat(dataRecord.batch_size)) * parseFloat(event.args.value) / 60;
+   dataRecord.boil_size = parseFloat(dataRecord.batch_size) + new_evap;
    dataRecord.boil_time = parseFloat(event.args.value);
-   dataRecord.boil_size = new_boil;
-   $('#boil_size').val(Round(new_boil, 2));
+   $('#boil_size').val(Round(dataRecord.boil_size, 2));
    calcFermentables();
-   // TODO: adjust the hops, miscs, yeast, water.
    calcIBUs();
   });
   $('#efficiency').on('change', function(event) {