diff --git a/controllers/StockApiController.php b/controllers/StockApiController.php
index 4578f64d..07b91151 100644
--- a/controllers/StockApiController.php
+++ b/controllers/StockApiController.php
@@ -119,6 +119,25 @@ class StockApiController extends BaseApiController
 		}
 	}
 
+	public function OpenProduct(\Slim\Http\Request $request, \Slim\Http\Response $response, array $args)
+	{
+		$specificStockEntryId = "default";
+		if (isset($request->getQueryParams()['stock_entry_id']) && !empty($request->getQueryParams()['stock_entry_id']))
+		{
+			$specificStockEntryId = $request->getQueryParams()['stock_entry_id'];
+		}
+
+		try
+		{
+			$bookingId = $this->StockService->OpenProduct($args['productId'], $args['amount'], $specificStockEntryId);
+			return $this->ApiResponse(array('booking_id' => $bookingId));
+		}
+		catch (\Exception $ex)
+		{
+			return $this->VoidApiActionResponse($response, false, 400, $ex->getMessage());
+		}
+	}
+
 	public function CurrentStock(\Slim\Http\Request $request, \Slim\Http\Response $response, array $args)
 	{
 		return $this->ApiResponse($this->StockService->GetCurrentStock());
diff --git a/grocy.openapi.json b/grocy.openapi.json
index 2438954e..85dc302d 100644
--- a/grocy.openapi.json
+++ b/grocy.openapi.json
@@ -1003,6 +1003,66 @@
 				}
 			}
 		},
+		"/stock/open-product/{productId}/{amount}": {
+			"get": {
+				"description": "Marks the the given amount of the given product as opened",
+				"tags": [
+					"Stock"
+				],
+				"parameters": [
+					{
+						"in": "path",
+						"name": "productId",
+						"required": true,
+						"description": "A valid product id",
+						"schema": {
+							"type": "integer"
+						}
+					},
+					{
+						"in": "path",
+						"name": "amount",
+						"required": false,
+						"description": "The amount to remove",
+						"schema": {
+							"type": "boolean",
+							"default": false
+						}
+					},
+					{
+						"in": "query",
+						"name": "stock_entry_id",
+						"required": false,
+						"description": "A specific stock entry id to open, if used, the amount has to be 1",
+						"schema": {
+							"type": "string"
+						}
+					}
+				],
+				"responses": {
+					"200": {
+						"description": "A VoidApiActionResponse object",
+						"content": {
+							"application/json": {
+								"schema": {
+									"$ref": "#/components/schemas/VoidApiActionResponse"
+								}
+							}
+						}
+					},
+					"400": {
+						"description": "A VoidApiActionResponse object (possible errors are: Not existing product)",
+						"content": {
+							"application/json": {
+								"schema": {
+									"$ref": "#/components/schemas/ErrorExampleVoidApiActionResponse"
+								}
+							}
+						}
+					}
+				}
+			}
+		},
 		"/stock/inventory-product/{productId}/{newAmount}": {
 			"get": {
 				"description": "Inventories the the given product (adds/removes based on the given new current amount)",
diff --git a/localization/en/stock_transaction_types.php b/localization/en/stock_transaction_types.php
index 22a57178..24d87eff 100644
--- a/localization/en/stock_transaction_types.php
+++ b/localization/en/stock_transaction_types.php
@@ -3,5 +3,6 @@
 return array(
 	'purchase' => 'Purchase',
 	'consume' => 'Consume',
-	'inventory-correction' => 'Inventory correction'
+	'inventory-correction' => 'Inventory correction',
+	'product-opened' => 'Product opened'
 );
diff --git a/localization/en/strings.php b/localization/en/strings.php
index 04895cba..c27df1fd 100644
--- a/localization/en/strings.php
+++ b/localization/en/strings.php
@@ -308,5 +308,13 @@ return array(
 	'Adding shopping list item #1 of #2' => 'Adding shopping list item #1 of #2',
 	'Use a specific stock item' => 'Use a specific stock item',
 	'Expires on #1; bought on #2' => 'Expires on #1; bought on #2',
-	'The first item in this list would be picked by the default rule which is "First expiring first, then first in first out"' => 'The first item in this list would be picked by the default rule which is "First expiring first, then first in first out"'
+	'The first item in this list would be picked by the default rule which is "First expiring first, then first in first out"' => 'The first item in this list would be picked by the default rule which is "First expiring first, then first in first out"',
+	'Mark #3 #1 of #2 as open' => 'Mark #3 #1 of #2 as open',
+	'When a product was marked as opened, the best before date will be replaced by today + this amount of days (a value of 0 disables this)' => 'When a product was marked as opened, the best before date will be replaced by today + this amount of days (a value of 0 disables this)',
+	'Default best before days after opened' => 'Default best before days after opened',
+	'Marked #1 #2 of #3 as opened' => 'Marked #1 #2 of #3 as opened',
+	'Mark as opened' => 'Mark as opened',
+	'Expires on #1; Bought on #2' => 'Expires on #1; Bought on #2',
+	'Not opened' => 'Not opened',
+	'Opened' => 'Opened'
 );
diff --git a/migrations/0046.sql b/migrations/0046.sql
new file mode 100644
index 00000000..262b1d6b
--- /dev/null
+++ b/migrations/0046.sql
@@ -0,0 +1,17 @@
+ALTER TABLE stock
+ADD opened_date DATETIME;
+
+ALTER TABLE stock_log
+ADD opened_date DATETIME;
+
+ALTER TABLE stock
+ADD open TINYINT NOT NULL DEFAULT 0 CHECK(open IN (0, 1));
+
+UPDATE stock
+SET open = 0;
+
+ALTER TABLE products
+ADD default_best_before_days_after_open INTEGER NOT NULL DEFAULT 0;
+
+UPDATE products
+SET default_best_before_days_after_open = 0;
diff --git a/public/viewjs/consume.js b/public/viewjs/consume.js
index 1208b85a..3b57b69e 100644
--- a/public/viewjs/consume.js
+++ b/public/viewjs/consume.js
@@ -23,7 +23,7 @@
 	}
 
 	Grocy.Api.Get('stock/get-product-details/' + jsonForm.product_id,
-		function (productDetails)
+		function(productDetails)
 		{
 			Grocy.Api.Get(apiUrl,
 				function(result)
@@ -54,6 +54,56 @@
 	);
 });
 
+$('#save-mark-as-open-button').on('click', function(e)
+{
+	e.preventDefault();
+
+	var jsonForm = $('#consume-form').serializeJSON();
+
+	if ($("#use_specific_stock_entry").is(":checked"))
+	{
+		jsonForm.amount = 1;
+	}
+
+	var apiUrl = 'stock/open-product/' + jsonForm.product_id + '/' + jsonForm.amount;
+
+	if ($("#use_specific_stock_entry").is(":checked"))
+	{
+		apiUrl += "&stock_entry_id=" + jsonForm.specific_stock_entry;
+	}
+
+	Grocy.Api.Get('stock/get-product-details/' + jsonForm.product_id,
+		function(productDetails)
+		{
+			Grocy.Api.Get(apiUrl,
+				function(result)
+				{
+					$("#specific_stock_entry").find("option").remove().end().append("<option></option>");
+					if ($("#use_specific_stock_entry").is(":checked"))
+					{
+						$("#use_specific_stock_entry").click();
+					}
+
+					toastr.success(L('Marked #1 #2 of #3 as opened', jsonForm.amount, Pluralize(jsonForm.amount, productDetails.quantity_unit_stock.name, productDetails.quantity_unit_stock.name_plural), productDetails.product.name) + '<br><a class="btn btn-secondary btn-sm mt-2" href="#" onclick="UndoStockBooking(' + result.booking_id + ')"><i class="fas fa-undo"></i> ' + L("Undo") + '</a>');
+
+					$('#amount').val(1);
+					Grocy.Components.ProductPicker.SetValue('');
+					Grocy.Components.ProductPicker.GetInputElement().focus();
+					Grocy.FrontendHelpers.ValidateForm('consume-form');
+				},
+				function(xhr)
+				{
+					console.error(xhr);
+				}
+			);
+		},
+		function(xhr)
+		{
+			console.error(xhr);
+		}
+	);
+});
+
 Grocy.Components.ProductPicker.GetPicker().on('change', function(e)
 {
 	$("#specific_stock_entry").find("option").remove().end().append("<option></option>");
@@ -99,11 +149,17 @@ Grocy.Components.ProductPicker.GetPicker().on('change', function(e)
 			{
 				stockEntries.forEach(stockEntry =>
 				{
+					var openTxt = L("Not opened");
+					if (stockEntry.open == 1)
+					{
+						openTxt = L("Opened");
+					}
+
 					for (i = 0; i < stockEntry.amount; i++)
 					{
 						$("#specific_stock_entry").append($("<option>", {
 							value: stockEntry.stock_id,
-							text: L("Expires on #1; bought on #2", moment(stockEntry.best_before_date).format("YYYY-MM-DD"), moment(stockEntry.purchased_date).format("YYYY-MM-DD"))
+							text: L("Expires on #1; Bought on #2", moment(stockEntry.best_before_date).format("YYYY-MM-DD"), moment(stockEntry.purchased_date).format("YYYY-MM-DD")) + "; " + openTxt
 						}));
 					}
 				});
diff --git a/public/viewjs/stockoverview.js b/public/viewjs/stockoverview.js
index 611e7520..74264426 100644
--- a/public/viewjs/stockoverview.js
+++ b/public/viewjs/stockoverview.js
@@ -152,6 +152,64 @@ $(document).on('click', '.product-consume-button', function(e)
 	);
 });
 
+$(document).on('click', '.product-open-button', function(e)
+{
+	e.preventDefault();
+
+	// Remove the focus from the current button
+	// to prevent that the tooltip stays until clicked anywhere else
+	document.activeElement.blur();
+	
+	var productId = $(e.currentTarget).attr('data-product-id');
+	var productName = $(e.currentTarget).attr('data-product-name');
+	var productQuName = $(e.currentTarget).attr('data-product-qu-name');
+
+	Grocy.Api.Get('stock/open-product/' + productId + '/1',
+		function()
+		{
+			Grocy.Api.Get('stock/get-product-details/' + productId,
+				function(result)
+				{
+					var productRow = $('#product-' + productId + '-row');
+					var expiringThreshold = moment().add("-" + $("#info-expiring-products").data("next-x-days"), "days");
+					var now = moment();
+					var nextBestBeforeDate = moment(result.next_best_before_date);
+
+					productRow.removeClass("table-warning");
+					productRow.removeClass("table-danger");
+					if (now.isAfter(nextBestBeforeDate))
+					{
+						productRow.addClass("table-danger");
+					}
+					if (expiringThreshold.isAfter(nextBestBeforeDate))
+					{
+						productRow.addClass("table-warning");
+					}
+
+					$('#product-' + productId + '-next-best-before-date').parent().effect('highlight', {}, 500);
+					$('#product-' + productId + '-next-best-before-date').fadeOut(500, function ()
+					{
+						$(this).text(result.next_best_before_date).fadeIn(500);
+					});
+					$('#product-' + productId + '-next-best-before-date-timeago').attr('datetime', result.next_best_before_date);
+
+					toastr.success(L('Marked #1 #2 of #3 as opened', 1, productQuName, productName));
+					RefreshContextualTimeago();
+					RefreshStatistics();
+				},
+				function(xhr)
+				{
+					console.error(xhr);
+				}
+			);
+		},
+		function(xhr)
+		{
+			console.error(xhr);
+		}
+	);
+});
+
 $(document).on("click", ".product-name-cell", function(e)
 {
 	Grocy.Components.ProductCard.Refresh($(e.currentTarget).attr("data-product-id"));
diff --git a/routes.php b/routes.php
index 17975a0a..44f9c1a2 100644
--- a/routes.php
+++ b/routes.php
@@ -108,6 +108,7 @@ $app->group('/api', function()
 	// Stock
 	$this->get('/stock/add-product/{productId}/{amount}', '\Grocy\Controllers\StockApiController:AddProduct');
 	$this->get('/stock/consume-product/{productId}/{amount}', '\Grocy\Controllers\StockApiController:ConsumeProduct');
+	$this->get('/stock/open-product/{productId}/{amount}', '\Grocy\Controllers\StockApiController:OpenProduct');
 	$this->get('/stock/inventory-product/{productId}/{newAmount}', '\Grocy\Controllers\StockApiController:InventoryProduct');
 	$this->get('/stock/get-product-details/{productId}', '\Grocy\Controllers\StockApiController:ProductDetails');
 	$this->get('/stock/get-product-price-history/{productId}', '\Grocy\Controllers\StockApiController:ProductPriceHistory');
diff --git a/services/StockService.php b/services/StockService.php
index 7c411f4d..100fa6dd 100644
--- a/services/StockService.php
+++ b/services/StockService.php
@@ -7,6 +7,7 @@ class StockService extends BaseService
 	const TRANSACTION_TYPE_PURCHASE = 'purchase';
 	const TRANSACTION_TYPE_CONSUME = 'consume';
 	const TRANSACTION_TYPE_INVENTORY_CORRECTION = 'inventory-correction';
+	const TRANSACTION_TYPE_PRODUCT_OPENED = 'product-opened';
 
 	public function GetCurrentStock($includeNotInStockButMissingProducts = false)
 	{
@@ -91,11 +92,19 @@ class StockService extends BaseService
 		return $returnData;
 	}
 
-	public function GetProductStockEntries($productId)
+	public function GetProductStockEntries($productId, $excludeOpened = false)
 	{
 		// In order of next use:
 		// First expiring first, then first in first out
-		return $this->Database->stock()->where('product_id', $productId)->orderBy('best_before_date', 'ASC')->orderBy('purchased_date', 'ASC')->fetchAll();
+
+		if ($excludeOpened)
+		{
+			return $this->Database->stock()->where('product_id = :1 AND open = 0', $productId)->orderBy('best_before_date', 'ASC')->orderBy('purchased_date', 'ASC')->fetchAll();
+		}
+		else
+		{
+			return $this->Database->stock()->where('product_id', $productId)->orderBy('best_before_date', 'ASC')->orderBy('purchased_date', 'ASC')->fetchAll();
+		}
 	}
 
 	public function AddProduct(int $productId, int $amount, string $bestBeforeDate, $transactionType, $purchasedDate, $price)
@@ -180,7 +189,8 @@ class StockService extends BaseService
 						'spoiled' => $spoiled,
 						'stock_id' => $stockEntry->stock_id,
 						'transaction_type' => $transactionType,
-						'price' => $stockEntry->price
+						'price' => $stockEntry->price,
+						'opened_date' => $stockEntry->opened_date
 					));
 					$logRow->save();
 
@@ -198,7 +208,8 @@ class StockService extends BaseService
 						'spoiled' => $spoiled,
 						'stock_id' => $stockEntry->stock_id,
 						'transaction_type' => $transactionType,
-						'price' => $stockEntry->price
+						'price' => $stockEntry->price,
+						'opened_date' => $stockEntry->opened_date
 					));
 					$logRow->save();
 
@@ -243,6 +254,91 @@ class StockService extends BaseService
 		return $this->Database->lastInsertId();
 	}
 
+	public function OpenProduct(int $productId, int $amount, $specificStockEntryId = 'default')
+	{
+		if (!$this->ProductExists($productId))
+		{
+			throw new \Exception('Product does not exist');
+		}
+
+		$productStockAmount = $this->Database->stock()->where('product_id', $productId)->sum('amount');
+		$potentialStockEntries = $this->GetProductStockEntries($productId, true);
+		$product = $this->Database->products($productId);
+
+		if ($amount > $productStockAmount)
+		{
+			return false;
+		}
+
+		if ($specificStockEntryId !== 'default')
+		{
+			$potentialStockEntries = FindAllObjectsInArrayByPropertyValue($potentialStockEntries, 'stock_id', $specificStockEntryId);
+		}
+
+		foreach ($potentialStockEntries as $stockEntry)
+		{
+			if ($amount == 0)
+			{
+				break;
+			}
+
+			$newBestBeforeDate = $stockEntry->best_before_date;
+			if ($product->default_best_before_days_after_open > 0)
+			{
+				 $newBestBeforeDate = date("Y-m-d", (strtotime('+' . $product->default_best_before_days_after_open . ' days')));
+			}
+
+			if ($amount >= $stockEntry->amount) //Take the whole stock entry
+			{
+				$logRow = $this->Database->stock_log()->createRow(array(
+					'product_id' => $stockEntry->product_id,
+					'amount' => $stockEntry->amount,
+					'best_before_date' => $stockEntry->best_before_date,
+					'purchased_date' => $stockEntry->purchased_date,
+					'stock_id' => $stockEntry->stock_id,
+					'transaction_type' => self::TRANSACTION_TYPE_PRODUCT_OPENED,
+					'price' => $stockEntry->price,
+					'opened_date' => date('Y-m-d')
+				));
+				$logRow->save();
+
+				$amount -= $stockEntry->amount;
+
+				$stockEntry->update(array(
+					'open' => 1,
+					'opened_date' => date('Y-m-d'),
+					'best_before_date' => $newBestBeforeDate
+				));
+			}
+			else //Stock entry amount is > than needed amount -> split the stock entry resp. update the amount
+			{
+				$logRow = $this->Database->stock_log()->createRow(array(
+					'product_id' => $stockEntry->product_id,
+					'amount' => $amount,
+					'best_before_date' => $stockEntry->best_before_date,
+					'purchased_date' => $stockEntry->purchased_date,
+					'stock_id' => $stockEntry->stock_id,
+					'transaction_type' => self::TRANSACTION_TYPE_PRODUCT_OPENED,
+					'price' => $stockEntry->price,
+					'opened_date' => date('Y-m-d')
+				));
+				$logRow->save();
+
+				$restStockAmount = $stockEntry->amount - $amount;
+				$amount = 0;
+
+				$stockEntry->update(array(
+					'amount' => $restStockAmount,
+					'open' => 1,
+					'opened_date' => date('Y-m-d'),
+					'best_before_date' => $newBestBeforeDate
+				));
+			}
+		}
+
+		return $this->Database->lastInsertId();
+	}
+
 	public function AddMissingProductsToShoppingList()
 	{
 		$missingProducts = $this->GetMissingProducts();
@@ -365,6 +461,21 @@ class StockService extends BaseService
 				'undone_timestamp' => date('Y-m-d H:i:s')
 			));
 		}
+		elseif ($logRow->transaction_type === self::TRANSACTION_TYPE_PRODUCT_OPENED)
+		{
+			// Remove opened flag from corresponding log entry
+			$stockRows = $this->Database->stock()->where('stock_id = :1 AND amount = :2', $logRow->stock_id, $logRow->amount);
+			$stockRows->update(array(
+				'open' => 0,
+				'opened_date' => null
+			));
+
+			// Update log entry
+			$logRow->update(array(
+				'undone' => 1,
+				'undone_timestamp' => date('Y-m-d H:i:s')
+			));
+		}
 		else
 		{
 			throw new \Exception('This booking cannot be undone');
diff --git a/views/consume.blade.php b/views/consume.blade.php
index 214c7cbd..f6521491 100644
--- a/views/consume.blade.php
+++ b/views/consume.blade.php
@@ -43,6 +43,7 @@
 			</div>
 
 			<button id="save-consume-button" class="btn btn-success">{{ $L('OK') }}</button>
+			<button id="save-mark-as-open-button" class="btn btn-secondary">{{ $L('Mark as opened') }}</button>
 
 		</form>
 	</div>
diff --git a/views/productform.blade.php b/views/productform.blade.php
index a6e149b4..79254479 100644
--- a/views/productform.blade.php
+++ b/views/productform.blade.php
@@ -73,6 +73,16 @@
 				'hint' => $L('For purchases this amount of days will be added to today for the best before date suggestion') . ' (' . $L('-1 means that this product never expires') . ')'
 			))
 
+			@php if($mode == 'edit') { $value = $product->default_best_before_days_after_open; } else { $value = 0; } @endphp
+			@include('components.numberpicker', array(
+				'id' => 'default_best_before_days_after_open',
+				'label' => 'Default best before days after opened',
+				'min' => 0,
+				'value' => $value,
+				'invalidFeedback' => $L('The amount cannot be lower than #1', '-1'),
+				'hint' => $L('When a product was marked as opened, the best before date will be replaced by today + this amount of days (a value of 0 disables this)')
+			))
+
 			<div class="form-group">
 				<label for="product_group_id">{{ $L('Product group') }}</label>
 				<select class="form-control" id="product_group_id" name="product_group_id">
diff --git a/views/stockoverview.blade.php b/views/stockoverview.blade.php
index 6ff692a2..77130846 100644
--- a/views/stockoverview.blade.php
+++ b/views/stockoverview.blade.php
@@ -97,6 +97,12 @@
 							data-consume-amount="{{ $currentStockEntry->amount }}">
 							<i class="fas fa-utensils"></i> {{ $L('All') }}
 						</a>
+						<a class="btn btn-success btn-sm product-open-button @if($currentStockEntry->amount == 0) disabled @endif" href="#" data-toggle="tooltip" data-placement="left" title="{{ $L('Mark #3 #1 of #2 as open', FindObjectInArrayByPropertyValue($quantityunits, 'id', FindObjectInArrayByPropertyValue($products, 'id', $currentStockEntry->product_id)->qu_id_stock)->name, FindObjectInArrayByPropertyValue($products, 'id', $currentStockEntry->product_id)->name, 1) }}"
+							data-product-id="{{ $currentStockEntry->product_id }}"
+							data-product-name="{{ FindObjectInArrayByPropertyValue($products, 'id', $currentStockEntry->product_id)->name }}"
+							data-product-qu-name="{{ FindObjectInArrayByPropertyValue($quantityunits, 'id', FindObjectInArrayByPropertyValue($products, 'id', $currentStockEntry->product_id)->qu_id_stock)->name }}">
+							<i class="fas fa-box-open"></i> 1
+						</a>
 						<a class="btn btn-info btn-sm" href="{{ $U('/stockjournal?product=') }}{{ $currentStockEntry->product_id }}">
 							<i class="fas fa-file-alt"></i>
 						</a>