diff --git a/addons/hr_holidays/models/hr_leave.py b/addons/hr_holidays/models/hr_leave.py
index 2d72154e76c..6f4a96b800b 100644
--- a/addons/hr_holidays/models/hr_leave.py
+++ b/addons/hr_holidays/models/hr_leave.py
@@ -12,11 +12,10 @@ from odoo.exceptions import UserError, AccessError, ValidationError
 from odoo.tools import float_compare
 from odoo.tools.translate import _
 
+from odoo.addons.resource.models.resource import HOURS_PER_DAY
+
 _logger = logging.getLogger(__name__)
 
-
-HOURS_PER_DAY = 8
-
 class HolidaysRequest(models.Model):
     _name = "hr.leave"
     _description = "Leave"
diff --git a/addons/resource/data/resource_data.xml b/addons/resource/data/resource_data.xml
index bcfd2c91446..84d0e86f46e 100644
--- a/addons/resource/data/resource_data.xml
+++ b/addons/resource/data/resource_data.xml
@@ -24,6 +24,7 @@
     <record id="resource_calendar_std_35h" model="resource.calendar">
         <field name="name">Standard 35 Hours/Week</field>
         <field name="company_id" ref="base.main_company"/>
+        <field name="hours_per_day">7.0</field>
         <field name="attendance_ids"
             eval="[
                 (0, 0, {'name': 'Monday Morning', 'dayofweek': '0', 'hour_from': 8, 'hour_to': 12}),
@@ -43,6 +44,7 @@
     <record id="resource_calendar_std_38h" model="resource.calendar">
         <field name="name">Standard 38 Hours/Week</field>
         <field name="company_id" ref="base.main_company"/>
+        <field name="hours_per_day">7.6</field>
         <field name="attendance_ids"
             eval="[
                 (0, 0, {'name': 'Monday Morning', 'dayofweek': '0', 'hour_from': 8, 'hour_to': 12}),
diff --git a/addons/resource/models/resource.py b/addons/resource/models/resource.py
index bcf7799f161..5a34afa53a4 100644
--- a/addons/resource/models/resource.py
+++ b/addons/resource/models/resource.py
@@ -14,7 +14,12 @@ from operator import itemgetter
 from odoo import api, fields, models, _
 from odoo.addons.base.models.res_partner import _tz_get
 from odoo.exceptions import ValidationError
-from odoo.tools.float_utils import float_compare
+from odoo.tools.float_utils import float_compare, float_round
+
+# Default hour per day value. The one should
+# only be used when the one from the calendar
+# is not available.
+HOURS_PER_DAY = 8
 
 
 def float_to_time(float_hour):
@@ -87,6 +92,15 @@ class ResourceCalendar(models.Model):
         'resource.calendar.leaves', 'calendar_id', 'Global Leaves',
         domain=[('resource_id', '=', False)]
         )
+    hours_per_day = fields.Float("Average hour per day", default=HOURS_PER_DAY, help="Average hours per day a resource is supposed to work with this calendar.")
+
+    @api.onchange('attendance_ids')
+    def _onchange_hours_per_day(self):
+        attendances = self.attendance_ids.filtered(lambda attendance: not attendance.date_from and not attendance.date_to)
+        hour_count = 0.0
+        for attendance in attendances:
+            hour_count += attendance.hour_to - attendance.hour_from
+        self.hours_per_day = float_round(hour_count / float(len(set(attendances.mapped('dayofweek')))), precision_digits=2)
 
     # --------------------------------------------------
     # Utility methods
@@ -645,6 +659,12 @@ class ResourceCalendarAttendance(models.Model):
     hour_to = fields.Float(string='Work to', required=True)
     calendar_id = fields.Many2one("resource.calendar", string="Resource's Calendar", required=True, ondelete='cascade')
 
+    @api.constrains('hour_from', 'hour_to')
+    def _check_hours(self):
+        for attendance in self:
+            if attendance.hour_from > attendance.hour_to:
+                raise ValidationError(_("The start-hour must be lower than end-hour."))
+
 
 class ResourceResource(models.Model):
     _name = "resource.resource"
diff --git a/addons/resource/views/resource_views.xml b/addons/resource/views/resource_views.xml
index b97129d6576..c7c2855b6bb 100644
--- a/addons/resource/views/resource_views.xml
+++ b/addons/resource/views/resource_views.xml
@@ -249,6 +249,7 @@
                     </h1>
                     <group>
                         <field name="company_id" groups="base.group_multi_company"/>
+                        <field name="hours_per_day"/>
                     </group>
                     <notebook>
                         <page string="Working Hours">