diff --git a/htdocs/expensereport/ajax/ajaxik.php b/htdocs/expensereport/ajax/ajaxik.php
index 6cd8c05fe5b..a02e7dd6c73 100644
--- a/htdocs/expensereport/ajax/ajaxik.php
+++ b/htdocs/expensereport/ajax/ajaxik.php
@@ -51,6 +51,8 @@ $langs->loadlangs(array('errors', 'trips'));
 
 $fk_expense = GETPOST('fk_expense', 'int');
 $fk_c_exp_tax_cat = GETPOST('fk_c_exp_tax_cat', 'int');
+$vatrate = GETPOST('vatrate', 'int');
+$qty = GETPOST('qty', 'int');
 
 // Security check
 $result = restrictedArea($user, 'expensereport', $fk_expense, 'expensereport');
@@ -61,30 +63,52 @@ $result = restrictedArea($user, 'expensereport', $fk_expense, 'expensereport');
  */
 
 top_httphead();
+$rep = new stdClass();
+$rep->response_status = 0;
+$rep->data = null;
+$rep->error = '';//@todo deprecated use error_message instead
+$rep->errorMessage = '';
+
 
 if (empty($fk_expense) || $fk_expense < 0) {
-	echo json_encode(array('error' => $langs->transnoentitiesnoconv('ErrorBadValueForParameter', $fk_expense, 'fk_expense')));
+	$rep->errorMessage =  json_encode(array('error' => $langs->transnoentitiesnoconv('ErrorBadValueForParameter', $fk_expense, 'fk_expense')));
 } elseif (empty($fk_c_exp_tax_cat) || $fk_c_exp_tax_cat < 0) {
-	echo json_encode(array('error' => $langs->transnoentitiesnoconv('ErrorBadValueForParameter', $fk_c_exp_tax_cat, 'fk_c_exp_tax_cat')));
+	$rep->errorMessage =  json_encode(array('error' => $langs->transnoentitiesnoconv('ErrorBadValueForParameter', $fk_c_exp_tax_cat, 'fk_c_exp_tax_cat')));
+
+	$rep->response_status = 'error';
 } else {
 	// @see ndfp.class.php:3576 (method: compute_total_km)
 	$expense = new ExpenseReport($db);
 	if ($expense->fetch($fk_expense) <= 0) {
-		echo json_encode(array('error' => $langs->transnoentitiesnoconv('ErrorRecordNotFound'), 'fk_expense' => $fk_expense));
+		$rep->errorMessage =  json_encode(array('error' => $langs->transnoentitiesnoconv('ErrorRecordNotFound'), 'fk_expense' => $fk_expense));
+		$rep->response_status = 'error';
 	} else {
 		$userauthor = new User($db);
 		if ($userauthor->fetch($expense->fk_user_author) <= 0) {
-			echo json_encode(array('error' => $langs->transnoentitiesnoconv('ErrorRecordNotFound'), 'fk_user_author' => $expense->fk_user_author));
+			$rep->errorMessage =  json_encode(array('error' => $langs->transnoentitiesnoconv('ErrorRecordNotFound'), 'fk_user_author' => $expense->fk_user_author));
+			$rep->response_status = 'error';
 		} else {
-			$expenseik = new ExpenseReportIk($db);
-			$range = $expenseik->getRangeByUser($userauthor, $fk_c_exp_tax_cat);
 
-			if (empty($range)) {
-				echo json_encode(array('error' => $langs->transnoentitiesnoconv('ErrorRecordNotFound'), 'range' => $range));
+			$expense = new ExpenseReport($db);
+			$result = $expense->computeTotalKm($fk_c_exp_tax_cat,$qty,$vatrate);
+			if ($result < 0){
+				$rep->error = $result;
+				$rep->errorMessage = $langs->trans('errorComputeTtcOnMileageExpense');
+				$rep->response_status = 'error';
+			}else{
+				$rep->data = $result;
+				$rep->response_status = 'success';
+			}
+
+			/*if (empty($range)) {
+				$rep->errorMessage =  json_encode(array('error' => $langs->transnoentitiesnoconv('ErrorRecordNotFound'), 'range' => $range));
+				$rep->response_status = 'error';
 			} else {
 				$ikoffset = price($range->ikoffset, 0, $langs, 1, -1, -1, $conf->currency);
-				echo json_encode(array('up' => $range->coef, 'ikoffset' => $range->ikoffset, 'title' => $langs->transnoentitiesnoconv('ExpenseRangeOffset', $ikoffset), 'comment' => 'offset should be applied on addline or updateline'));
-			}
+				$rep->errorMessage =  json_encode(array('up' => $range->coef, 'ikoffset' => $range->ikoffset, 'title' => $langs->transnoentitiesnoconv('ExpenseRangeOffset', $ikoffset), 'comment' => 'offset should be applied on addline or updateline'));
+				$rep->response_status = 'error';
+			}*/
 		}
 	}
 }
+echo json_encode($rep);
diff --git a/htdocs/expensereport/card.php b/htdocs/expensereport/card.php
index c1aebe67534..c14edaa68da 100644
--- a/htdocs/expensereport/card.php
+++ b/htdocs/expensereport/card.php
@@ -2377,7 +2377,7 @@ if ($action == 'create') {
 
 						// Quantity
 						print '<td class="right">';
-						print '<input type="text" min="0" class="right maxwidth50" name="qty" value="'.dol_escape_htmltag($line->qty).'" />';  // We must be able to enter decimal qty
+						print '<input type="text" min="0" class="right maxwidth50" id="input_qty" name="qty" value="'.dol_escape_htmltag($line->qty).'" />';  // We must be able to enter decimal qty
 						print '</td>';
 
 						//print '<td class="right">'.$langs->trans('AmountHT').'</td>';
@@ -2559,7 +2559,7 @@ if ($action == 'create') {
 
 				// Quantity
 				print '<td class="right inputqty">';
-				print '<input type="text" min="0" class="right maxwidth50" name="qty" value="'.dol_escape_htmltag($qty ? $qty : 1).'">'; // We must be able to enter decimal qty
+				print '<input type="text" min="0" class="right maxwidth50" id="input_qty" name="qty" value="'.dol_escape_htmltag($qty ? $qty : 1).'">'; // We must be able to enter decimal qty
 				print '</td>';
 
 				// Picture
@@ -2579,7 +2579,7 @@ if ($action == 'create') {
 
 			print '</table>';
 			print '</div>';
-
+			//var_dump($object);
 			print '<script javascript>
 
 			/* JQuery for product free or predefined select */
@@ -2596,6 +2596,51 @@ if ($action == 'create') {
 						jQuery("#value_unit_ht").val("");
 					}
 				});
+
+                /* price calculation */
+                jQuery("#input_qty, #fk_c_type_fees, #select_fk_c_exp_tax_cat, #vatrate ").change(function(event) {
+
+                    let type_fee = jQuery("#fk_c_type_fees").find(":selected").val();
+                    let tax_cat = jQuery("#select_fk_c_exp_tax_cat").find(":selected").val();
+                    let tva = jQuery("#vatrate").find(":selected").val();
+                    let qty = jQuery("#input_qty").val();
+
+
+					let path = "'.dol_buildpath("/expensereport/ajax/ajaxik.php", 1) .'";
+					path += "?fk_c_exp_tax_cat="+tax_cat;
+					path +="&fk_expense="+'.$object->id.';
+                    path += "&vatrate="+tva;
+                    path += "&qty="+qty;
+
+                    if (type_fee == 4) { // frais_kilométriques
+
+						jQuery.ajax({
+							url: path
+							,async:false
+							,dataType:"json"
+							,success:function(response) {
+                                if (response.response_status == "success"){
+
+                                jQuery("#value_unit_ht").val(response.data);
+                                }else{
+								  console.log(response.errorMessage)
+                                }
+
+							},
+
+						});
+
+
+                    }else{
+                        console.log("not a type concerned");
+                    }
+
+					/*console.log(event.which);		// discard event tag and arrows
+					if (event.which != 9 && (event.which < 37 || event.which > 40) && jQuery("#value_unit").val() != "") {
+						jQuery("#value_unit_ht").val("");
+					}*/
+				});
+
 			});
 
 			</script>';
diff --git a/htdocs/expensereport/class/expensereport.class.php b/htdocs/expensereport/class/expensereport.class.php
index 9a69784adce..1d054eeb466 100644
--- a/htdocs/expensereport/class/expensereport.class.php
+++ b/htdocs/expensereport/class/expensereport.class.php
@@ -398,7 +398,6 @@ class ExpenseReport extends CommonObject
 		}
 	}
 
-
 	/**
 	 *	Load an object from its id and create a new one in database
 	 *
@@ -2559,6 +2558,105 @@ class ExpenseReport extends CommonObject
 			return -1;
 		}
 	}
+
+	/**
+	 *  \brief Compute the cost of the kilometers expense based on the number of kilometers and the vehicule category
+	 *
+	 *  @param     fk_cat           Category of the vehicule used
+	 *  @param     qty              Number of kilometers
+	 *  @param     tva              VAT rate
+	 *  @return    int              <0 if KO, total ttc if OK
+	 */
+	function computeTotalKm($fk_cat, $qty, $tva)
+	{
+		global $langs,$user,$db,$conf;
+
+		$total_ttc = 0;
+		$ranges = array();
+		$coef = 0;
+		$offset = 0;
+
+		if ($fk_cat < 0){
+			$this->error = $langs->trans('ErrorBadParameterCat');
+			return -1;
+		}
+
+		if ($qty <= 0){
+			$this->error = $langs->trans('ErrorBadParameterQty');
+			return -1;
+		}
+
+		$currentUser = new User($db);
+		$currentUser->fetch($this->fk_user);
+		$currentUser->getrights('expensereport');
+		//Clean
+		$qty = price2num($qty);
+
+		$sql  = " SELECT r.range_ik, t.offset, t.coef";
+		$sql .= " FROM ".MAIN_DB_PREFIX."c_exp_tax t";
+		$sql .= " LEFT JOIN ".MAIN_DB_PREFIX."c_exp_tax_range r ON r.rowid = t.fk_range";
+		$sql .= " WHERE t.fk_cat = ".$fk_cat;
+		$sql .= " ORDER BY r.range_ik ASC";
+		dol_syslog("expenseReport::computeTotalkm sql=".$sql, LOG_DEBUG);
+
+		$result = $this->db->query($sql);
+
+		if ($result)
+		{
+			$num = $this->db->num_rows($result);
+
+			if ($num)
+			{
+				for ($i = 0; $i < $num; $i++)
+				{
+					$obj = $this->db->fetch_object($result);
+
+					$ranges[$i] = $obj;
+				}
+
+
+					for ($i = 0; $i < $num; $i++)
+					{
+						if ($i < ($num - 1))
+						{
+							if ($qty > $ranges[$i]->range && $qty < $ranges[$i+1]->range)
+							{
+								$coef = $ranges[$i]->coef;
+								$offset = $ranges[$i]->offset;
+							}
+						}
+						else
+						{
+							if ($qty > $ranges[$i]->range)
+							{
+								$coef = $ranges[$i]->coef;
+								$offset = $ranges[$i]->offset;
+							}
+						}
+					}
+
+				$total_ht = $coef;
+				//$total_ttc = price2num($total_ht + ( $total_ht * $tva / 100),'MT');
+				return $total_ht;
+			}
+			else
+			{
+				$this->error = $langs->trans('TaxUndefinedForThisCategory');
+
+				return -1;
+			}
+
+		}
+		else
+		{
+			$this->error = $this->db->error()." sql=".$sql;
+
+			return -1;
+		}
+	}
+
+
+
 }
 
 
@@ -2941,4 +3039,6 @@ class ExpenseReportLine extends CommonObjectLine
 			return -2;
 		}
 	}
+
+	// ajouter ici comput_ ...
 }
diff --git a/htdocs/expensereport/class/expensereport_ik.class.php b/htdocs/expensereport/class/expensereport_ik.class.php
index 49ac0af9857..0d374f1c722 100644
--- a/htdocs/expensereport/class/expensereport_ik.class.php
+++ b/htdocs/expensereport/class/expensereport_ik.class.php
@@ -197,12 +197,13 @@ class ExpenseReportIk extends CommonObject
 	{
 		$default_range = (int) $userauthor->default_range; // if not defined, then 0
 		$ranges = $this->getRangesByCategory($fk_c_exp_tax_cat);
-
+		// prevent out of range -1 indice
+		$indice = $default_range > 0 ? $default_range - 1 : 0;
 		// substract 1 because array start from 0
-		if (empty($ranges) || !isset($ranges[$default_range - 1])) {
+		if (empty($ranges) || !isset($ranges[$indice])) {
 			return false;
 		} else {
-			return $ranges[$default_range - 1];
+			return $ranges[$indice];
 		}
 	}