diff --git a/library/src/calculator_functions.cpp b/library/src/calculator_functions.cpp
index fe133f1..6a92ee3 100644
--- a/library/src/calculator_functions.cpp
+++ b/library/src/calculator_functions.cpp
@@ -117,6 +117,117 @@ QDateTime Calculator::GetDailyTicketDuration(Configuration* cfg, const QDateTime
 
     return QDateTime();
 }
+
+int Calculator::computeBruttoDurationInSecs(Configuration const *cfg,
+                                            QDateTime const &start,
+                                            int nettoDurationInSecs,
+                                            bool maxBrutto) {
+    QDateTime from(start);
+    int bruttoDurationInSecs = 0;
+
+    if (DBG_LEVEL >= DBG_DEBUG) {
+        qCritical() << DBG_HEADER << "netto duration in secs" << nettoDurationInSecs;
+    }
+
+    while (nettoDurationInSecs > 0) {
+        int day_in_week_id = from.date().dayOfWeek();
+        int count = cfg->WeekDaysWorktime.count(day_in_week_id);
+
+        if (DBG_LEVEL >= DBG_DEBUG) {
+            qCritical() << DBG_HEADER << "count for " << day_in_week_id << ": " << count;
+        }
+
+        if (count > 0) {
+            for (auto[iter, rEnd] = cfg->WeekDaysWorktime.equal_range(day_in_week_id); iter != rEnd; ++iter) {
+                QTime const &pwd_time_from = QTime::fromString(QString::fromStdString(iter->second.pwd_time_from), Qt::ISODate);
+                QTime const &pwd_time_to = QTime::fromString(QString::fromStdString(iter->second.pwd_time_to), Qt::ISODate);
+                QTime fromTime = from.time();
+
+                if (DBG_LEVEL >= DBG_DEBUG) {
+                    qCritical() << DBG_HEADER;
+                    qCritical() << DBG_HEADER << " wd-from" << pwd_time_from.toString(Qt::ISODate);
+                    qCritical() << DBG_HEADER << "   wd-to" << pwd_time_to.toString(Qt::ISODate);
+                    qCritical() << DBG_HEADER << "fromTime" << fromTime.toString(Qt::ISODate);
+                    qCritical() << DBG_HEADER << "    from" << from.toString(Qt::ISODate);
+                    qCritical() << DBG_HEADER;
+                }
+
+                if (fromTime <= pwd_time_from) {
+                    int secs = fromTime.secsTo(pwd_time_from);
+                    bruttoDurationInSecs += secs;
+                    fromTime = pwd_time_from;
+                    from.setTime(pwd_time_from);
+                }
+
+                if (DBG_LEVEL >= DBG_DEBUG) {
+                    qCritical() << DBG_HEADER << "fromTime" << fromTime.toString(Qt::ISODate);
+                    qCritical() << DBG_HEADER << "    from" << from.toString(Qt::ISODate);
+                    qCritical() << DBG_HEADER << "   netto" << nettoDurationInSecs;
+                    qCritical() << DBG_HEADER << "  brutto" << bruttoDurationInSecs;
+                    qCritical() << DBG_HEADER << " br-date" << start.addSecs(bruttoDurationInSecs);
+                }
+
+                while (fromTime < pwd_time_to && nettoDurationInSecs > 0) {
+                    bruttoDurationInSecs += 60;
+                    nettoDurationInSecs -= 60;
+                    fromTime = fromTime.addSecs(60);
+                    from = from.addSecs(60);
+                }
+
+                if (DBG_LEVEL >= DBG_DEBUG) {
+                    qCritical() << DBG_HEADER;
+                    qCritical() << DBG_HEADER << "   netto" << nettoDurationInSecs;
+                    qCritical() << DBG_HEADER << "  brutto" << bruttoDurationInSecs;
+                    qCritical() << DBG_HEADER << " br-date" << start.addSecs(bruttoDurationInSecs);
+                    qCritical() << DBG_HEADER << "fromTime" << fromTime.toString(Qt::ISODate);
+                    qCritical() << DBG_HEADER << "    from" << from.toString(Qt::ISODate);
+                    qCritical() << DBG_HEADER;
+                }
+
+                if (--count == 0 && fromTime == pwd_time_to) {
+                    // handle rest
+                    QDateTime midnight(from);
+                    midnight = midnight.addDays(1);
+                    midnight.setTime(QTime(0, 0, 0));
+                    int secs =  from.secsTo(midnight);
+                    bruttoDurationInSecs += secs;
+                    from = midnight;
+
+                    if (DBG_LEVEL >= DBG_DEBUG) {
+                        qCritical() << DBG_HEADER;
+                        qCritical() << DBG_HEADER << "   netto" << nettoDurationInSecs;
+                        qCritical() << DBG_HEADER << "  brutto" << bruttoDurationInSecs;
+                        qCritical() << DBG_HEADER << " br-date" << start.addSecs(bruttoDurationInSecs);
+                        qCritical() << DBG_HEADER << "    from" << from.toString(Qt::ISODate);
+                        qCritical() << DBG_HEADER;
+                    }
+                }
+            }
+
+        } else {
+            bruttoDurationInSecs += (24 * 3600);
+            from = from.addDays(1);
+        }
+    }
+
+    if (maxBrutto) {
+        qCritical() << DBG_HEADER << "TODO";
+    }
+
+    if (DBG_LEVEL >= DBG_DEBUG) {
+        qCritical() << DBG_HEADER << " br-date" << start.addSecs(bruttoDurationInSecs);
+    }
+
+    return bruttoDurationInSecs;
+}
+
+QDateTime Calculator::computeBruttoDateTime(Configuration const *cfg,
+                                            QDateTime const &from,
+                                            int durationInSecs,
+                                            bool maxBrutto) {
+    return from.addSecs(computeBruttoDurationInSecs(cfg, from, durationInSecs, maxBrutto));
+}
+
 /// <inheritdoc/>
 std::string Calculator::GetDurationFromCost(Configuration* cfg,
                                             uint8_t payment_option,