diff --git a/library/src/calculator_functions.cpp b/library/src/calculator_functions.cpp
index a47f0d9..5f1bee2 100644
--- a/library/src/calculator_functions.cpp
+++ b/library/src/calculator_functions.cpp
@@ -456,11 +456,13 @@ double Calculator::GetCostFromDuration(Configuration* cfg, uint8_t payment_optio
     double price_per_unit = 0.0f;
     QTime worktime_from;
     QTime worktime_to;
+    double durationUnit = 60.0;
 
     if(is_special_day)
     {
-        // Set special day price
-        price_per_unit = Utilities::CalculatePricePerUnit(day_price);
+        // Set price_per_unit to special day price: at the end of the calculation
+        // divide by durationUnit to get correct price.
+        price_per_unit = day_price;
         worktime_from = QTime::fromString(cfg->SpecialDaysWorktime.find(current_special_day_id)->second.pedwt_time_from.c_str());
         worktime_to = QTime::fromString(cfg->SpecialDaysWorktime.find(current_special_day_id)->second.pedwt_time_to.c_str());
     }
@@ -472,8 +474,13 @@ double Calculator::GetCostFromDuration(Configuration* cfg, uint8_t payment_optio
         day_price = cfg->PaymentRate.find(pop_id)->second.pra_price;
 
         int durationId = cfg->PaymentRate.find(pop_id)->second.pra_payment_unit_id;
-        double durationUnit = cfg->Duration.find(durationId)->second.pun_duration;
-        price_per_unit = Utilities::CalculatePricePerUnit(day_price,durationUnit);
+        durationUnit = cfg->Duration.find(durationId)->second.pun_duration;
+        if (durationUnit == 0) {
+            durationUnit = 60.0;
+        }
+        // Set price_per_unit to day price: at the end of the calculation
+        // divide by durationUnit to get correct price.
+        price_per_unit = day_price;
 
         // If no working day found, skip it (recursively call method again)
         size_t found = 0;
@@ -484,7 +491,7 @@ double Calculator::GetCostFromDuration(Configuration* cfg, uint8_t payment_optio
         {
             LOG_DEBUG("- No workday found, trying to find next available day");
             inputDate = inputDate.addDays(1);
-            return floor(GetCostFromDuration(cfg, payment_option, inputDate, end_datetime, durationMin, true, prepaid));
+            return GetCostFromDuration(cfg, payment_option, inputDate, end_datetime, durationMin, true, prepaid) / durationUnit;
         }
         worktime_from = QTime::fromString(cfg->WeekDaysWorktime.find(weekdayId)->second.pwd_time_from.c_str());
         worktime_to = QTime::fromString(cfg->WeekDaysWorktime.find(weekdayId)->second.pwd_time_to.c_str());
@@ -497,7 +504,7 @@ double Calculator::GetCostFromDuration(Configuration* cfg, uint8_t payment_optio
     {
         inputDate = inputDate.addDays(1);
         inputDate.setTime(worktime_from);
-        return GetCostFromDuration(cfg, payment_option, inputDate, end_datetime, durationMin, true, prepaid);
+        return GetCostFromDuration(cfg, payment_option, inputDate, end_datetime, durationMin, true, prepaid) / durationUnit;
     }
 
     // If overtime flag is set
@@ -527,7 +534,7 @@ double Calculator::GetCostFromDuration(Configuration* cfg, uint8_t payment_optio
         {
             LOG_DEBUG(" *** PREPAID *** Current time is past the time range end, searching for next available day");
             inputDate = inputDate.addDays(1);
-            return GetCostFromDuration(cfg, payment_option, inputDate, end_datetime, durationMin, true, prepaid);
+            return GetCostFromDuration(cfg, payment_option, inputDate, end_datetime, durationMin, true, prepaid) / durationUnit;
         }
     }
 
@@ -579,7 +586,7 @@ double Calculator::GetCostFromDuration(Configuration* cfg, uint8_t payment_optio
             LOG_DEBUG("Reached end of worktime, searching for the next working day");
             inputDate = inputDate.addDays(1);
             overtime = true;
-            return GetCostFromDuration(cfg, payment_option, inputDate, end_datetime, total_duration_min);
+            return GetCostFromDuration(cfg, payment_option, inputDate, end_datetime, total_duration_min) / durationUnit;
         }
 
         // Increment input date minutes for each monetary unit
@@ -594,7 +601,7 @@ double Calculator::GetCostFromDuration(Configuration* cfg, uint8_t payment_optio
 
     double ret_val = total_cost;
     total_cost = 0.0f;
-    return ceil(ret_val);
+    return round(ret_val / durationUnit);
 }