diff --git a/changelog/81_UNRELEASED_xxxx-xx-xx.md b/changelog/81_UNRELEASED_xxxx-xx-xx.md
index 67f22f48..0635e5c7 100644
--- a/changelog/81_UNRELEASED_xxxx-xx-xx.md
+++ b/changelog/81_UNRELEASED_xxxx-xx-xx.md
@@ -10,6 +10,11 @@
 
 ### Stock
 
+- Optimized product definition quantity unit handling:
+  - As long as a product was not once in stock, the product options "Default quantity unit purchase", "Default quantity unit consume" and "Quantity unit for prices" can now be changed to any other unit
+  - When necessary (means when no default quantity unit conversions apply), "1:1" product specific quantity unit conversion between the product's QU stock and the corresponding other unit will now be created automatically after editing a product (like already done when initially creating a product with different unit definitions)
+  - For convenience, when changing a product's QU stock and when all other unit properties ("Default quantity unit purchase" etc.) are the same, they will now be changed in tandem (like already done when creating a new product and initially setting the product's QU stock)
+  - (This should drastically improve the workflow of completing a product setup looked up via an external barcode lookup plugin)
 - Optimized the line plot markers color of the price history chart (product card) (thanks @DeepCoreSystem)
 - External barcode lookup plugin optimizations:
   - When an image URL without a file extension is returned, the file extension is now determined by the Content-Type header (if any) (thanks @jordy-u for the idea)
diff --git a/controllers/StockController.php b/controllers/StockController.php
index 408c29c7..09742aad 100644
--- a/controllers/StockController.php
+++ b/controllers/StockController.php
@@ -195,12 +195,13 @@ class StockController extends BaseController
 	{
 		if ($args['productId'] == 'new')
 		{
+			$quantityunits = $this->getDatabase()->quantity_units()->where('active = 1')->orderBy('name', 'COLLATE NOCASE');
+
 			return $this->renderPage($response, 'productform', [
 				'locations' => $this->getDatabase()->locations()->where('active = 1')->orderBy('name'),
 				'barcodes' => $this->getDatabase()->product_barcodes()->orderBy('barcode'),
-				'quantityunits' => $this->getDatabase()->quantity_units()->where('active = 1')->orderBy('name', 'COLLATE NOCASE'),
-				'quantityunitsStock' => $this->getDatabase()->quantity_units()->orderBy('name', 'COLLATE NOCASE'),
-				'referencedQuantityunits' => $this->getDatabase()->quantity_units()->where('active = 1')->orderBy('name', 'COLLATE NOCASE'),
+				'quantityunitsAll' => $quantityunits,
+				'quantityunitsReferenced' => $quantityunits,
 				'shoppinglocations' => $this->getDatabase()->shopping_locations()->where('active = 1')->orderBy('name', 'COLLATE NOCASE'),
 				'productgroups' => $this->getDatabase()->product_groups()->where('active = 1')->orderBy('name', 'COLLATE NOCASE'),
 				'userfields' => $this->getUserfieldsService()->GetFields('products'),
@@ -217,9 +218,8 @@ class StockController extends BaseController
 				'product' => $product,
 				'locations' => $this->getDatabase()->locations()->where('active = 1')->orderBy('name', 'COLLATE NOCASE'),
 				'barcodes' => $this->getDatabase()->product_barcodes()->orderBy('barcode'),
-				'quantityunits' => $this->getDatabase()->quantity_units()->where('active = 1')->orderBy('name', 'COLLATE NOCASE'),
-				'quantityunitsStock' => $this->getDatabase()->quantity_units()->where('id IN (SELECT to_qu_id FROM cache__quantity_unit_conversions_resolved WHERE product_id = :1) OR NOT EXISTS(SELECT 1 FROM stock_log WHERE product_id = :1)', $product->id)->orderBy('name', 'COLLATE NOCASE'),
-				'referencedQuantityunits' => $this->getDatabase()->quantity_units()->where('active = 1')->where('id IN (SELECT to_qu_id FROM cache__quantity_unit_conversions_resolved WHERE product_id = :1)', $product->id)->orderBy('name', 'COLLATE NOCASE'),
+				'quantityunitsAll' => $this->getDatabase()->quantity_units()->where('active = 1')->orderBy('name', 'COLLATE NOCASE'),
+				'quantityunitsReferenced' => $this->getDatabase()->quantity_units()->where('id IN (SELECT to_qu_id FROM cache__quantity_unit_conversions_resolved WHERE product_id = :1) OR NOT EXISTS(SELECT 1 FROM stock_log WHERE product_id = :1)', $product->id)->orderBy('name', 'COLLATE NOCASE'),
 				'shoppinglocations' => $this->getDatabase()->shopping_locations()->where('active = 1')->orderBy('name', 'COLLATE NOCASE'),
 				'productgroups' => $this->getDatabase()->product_groups()->where('active = 1')->orderBy('name', 'COLLATE NOCASE'),
 				'userfields' => $this->getUserfieldsService()->GetFields('products'),
diff --git a/localization/strings.pot b/localization/strings.pot
index bdb68303..dc8d22d2 100644
--- a/localization/strings.pot
+++ b/localization/strings.pot
@@ -2470,3 +2470,6 @@ msgstr ""
 
 msgid "List actions"
 msgstr ""
+
+msgid "After this product was once in stock and when the desired quantity unit cannot be selected here, first create a corresponding unit conversion"
+msgstr ""
diff --git a/migrations/0255.sql b/migrations/0255.sql
new file mode 100644
index 00000000..cdca7d16
--- /dev/null
+++ b/migrations/0255.sql
@@ -0,0 +1,66 @@
+DROP TRIGGER products_default_qu_conversions;
+CREATE TRIGGER products_default_qu_conversions_INS AFTER INSERT ON products
+BEGIN
+	-- Create product specific 1:1 conversions when QU stock != QU purchase/consume/price
+	-- and when no default QU conversion apply
+
+	-- with qu_id_stock != qu_id_purchase
+	INSERT INTO quantity_unit_conversions
+		(from_qu_id, to_qu_id, factor, product_id)
+	SELECT p.qu_id_purchase, p.qu_id_stock, 1, p.id
+	FROM products p
+	WHERE p.id = NEW.id
+		AND p.qu_id_stock != qu_id_purchase
+		AND NOT EXISTS(SELECT 1 FROM quantity_unit_conversions_resolved WHERE product_id = p.id AND from_qu_id = p.qu_id_stock AND to_qu_id = p.qu_id_purchase);
+
+	-- with qu_id_stock != qu_id_consume
+	INSERT INTO quantity_unit_conversions
+		(from_qu_id, to_qu_id, factor, product_id)
+	SELECT p.qu_id_consume, p.qu_id_stock, 1, p.id
+	FROM products p
+	WHERE p.id = NEW.id
+		AND p.qu_id_stock != qu_id_consume
+		AND NOT EXISTS(SELECT 1 FROM quantity_unit_conversions_resolved WHERE product_id = p.id AND from_qu_id = p.qu_id_stock AND to_qu_id = p.qu_id_consume);
+
+	-- with qu_id_stock != qu_id_price
+	INSERT INTO quantity_unit_conversions
+		(from_qu_id, to_qu_id, factor, product_id)
+	SELECT p.qu_id_price, p.qu_id_stock, 1, p.id
+	FROM products p
+	WHERE p.id = NEW.id
+		AND p.qu_id_stock != qu_id_price
+		AND NOT EXISTS(SELECT 1 FROM quantity_unit_conversions_resolved WHERE product_id = p.id AND from_qu_id = p.qu_id_stock AND to_qu_id = p.qu_id_price);
+END;
+
+CREATE TRIGGER products_default_qu_conversions_UPD AFTER UPDATE ON products
+BEGIN
+	-- Create product specific 1:1 conversions when QU stock != QU purchase/consume/price
+	-- and when no default QU conversion apply
+
+	-- with qu_id_stock != qu_id_purchase
+	INSERT INTO quantity_unit_conversions
+		(from_qu_id, to_qu_id, factor, product_id)
+	SELECT p.qu_id_purchase, p.qu_id_stock, 1, p.id
+	FROM products p
+	WHERE p.id = NEW.id
+		AND p.qu_id_stock != qu_id_purchase
+		AND NOT EXISTS(SELECT 1 FROM quantity_unit_conversions_resolved WHERE product_id = p.id AND from_qu_id = p.qu_id_stock AND to_qu_id = p.qu_id_purchase);
+
+	-- with qu_id_stock != qu_id_consume
+	INSERT INTO quantity_unit_conversions
+		(from_qu_id, to_qu_id, factor, product_id)
+	SELECT p.qu_id_consume, p.qu_id_stock, 1, p.id
+	FROM products p
+	WHERE p.id = NEW.id
+		AND p.qu_id_stock != qu_id_consume
+		AND NOT EXISTS(SELECT 1 FROM quantity_unit_conversions_resolved WHERE product_id = p.id AND from_qu_id = p.qu_id_stock AND to_qu_id = p.qu_id_consume);
+
+	-- with qu_id_stock != qu_id_price
+	INSERT INTO quantity_unit_conversions
+		(from_qu_id, to_qu_id, factor, product_id)
+	SELECT p.qu_id_price, p.qu_id_stock, 1, p.id
+	FROM products p
+	WHERE p.id = NEW.id
+		AND p.qu_id_stock != qu_id_price
+		AND NOT EXISTS(SELECT 1 FROM quantity_unit_conversions_resolved WHERE product_id = p.id AND from_qu_id = p.qu_id_stock AND to_qu_id = p.qu_id_price);
+END;
diff --git a/public/viewjs/productform.js b/public/viewjs/productform.js
index 6991a44c..a2f3002d 100644
--- a/public/viewjs/productform.js
+++ b/public/viewjs/productform.js
@@ -352,29 +352,33 @@ $(document).on('click', '.barcode-delete-button', function(e)
 	});
 });
 
+var quIdStockBefore = $("#qu_id_stock").val();
 $('#qu_id_stock').change(function(e)
 {
-	// Preset qu_id_purchase/qu_id_consume/qu_id_price by qu_id_stock if unset
+	// Preset qu_id_purchase / qu_id_consume / qu_id_price by qu_id_stock if unset or identical
+
 	var quIdStock = $('#qu_id_stock');
 	var quIdPurchase = $('#qu_id_purchase');
 	var quIdConsume = $('#qu_id_consume');
 	var quIdPrice = $('#qu_id_price');
 
-	if (quIdPurchase[0].selectedIndex === 0 && quIdStock[0].selectedIndex !== 0)
+	if (quIdPurchase[0].selectedIndex === 0 && quIdStock[0].selectedIndex !== 0 || quIdStockBefore == quIdPurchase.val())
 	{
 		quIdPurchase[0].selectedIndex = quIdStock[0].selectedIndex;
 	}
 
-	if (quIdConsume[0].selectedIndex === 0 && quIdStock[0].selectedIndex !== 0)
+	if (quIdConsume[0].selectedIndex === 0 && quIdStock[0].selectedIndex !== 0 || quIdStockBefore == quIdConsume.val())
 	{
 		quIdConsume[0].selectedIndex = quIdStock[0].selectedIndex;
 	}
 
-	if (quIdPrice[0].selectedIndex === 0 && quIdStock[0].selectedIndex !== 0)
+	if (quIdPrice[0].selectedIndex === 0 && quIdStock[0].selectedIndex !== 0 || quIdStockBefore == quIdPrice.val())
 	{
 		quIdPrice[0].selectedIndex = quIdStock[0].selectedIndex;
 	}
 
+	quIdStockBefore = quIdStock.val();
+
 	Grocy.FrontendHelpers.ValidateForm('product-form');
 });
 
diff --git a/views/productform.blade.php b/views/productform.blade.php
index b71436ec..da5c9f27 100644
--- a/views/productform.blade.php
+++ b/views/productform.blade.php
@@ -371,15 +371,19 @@
 
 			<div class="form-group">
 				<label for="qu_id_stock">{{ $__t('Quantity unit stock') }}</label>
+				<i class="fa-solid fa-question-circle text-muted"
+					data-toggle="tooltip"
+					data-trigger="hover click"
+					title="{{ $__t('After this product was once in stock and when the desired quantity unit cannot be selected here, first create a corresponding unit conversion') }}"></i>
 				<select required
 					class="custom-control custom-select input-group-qu"
 					id="qu_id_stock"
 					name="qu_id_stock">
 					<option></option>
-					@foreach($quantityunitsStock as $quantityunit)
+					@foreach($quantityunitsReferenced as $qu)
 					<option @if($mode=='edit'
 						&&
-						$quantityunit->id == $product->qu_id_stock) selected="selected" @endif value="{{ $quantityunit->id }}" data-plural-form="{{ $quantityunit->name_plural }}">{{ $quantityunit->name }}</option>
+						$qu->id == $product->qu_id_stock) selected="selected" @endif value="{{ $qu->id }}" data-plural-form="{{ $qu->name_plural }}">{{ $qu->name }}</option>
 					@endforeach
 				</select>
 				<div class="invalid-feedback">{{ $__t('A quantity unit is required') }}</div>
@@ -396,10 +400,10 @@
 					id="qu_id_purchase"
 					name="qu_id_purchase">
 					<option></option>
-					@foreach($referencedQuantityunits as $quantityunit)
+					@foreach($quantityunitsReferenced as $qu)
 					<option @if($mode=='edit'
 						&&
-						$quantityunit->id == $product->qu_id_purchase) selected="selected" @endif value="{{ $quantityunit->id }}">{{ $quantityunit->name }}</option>
+						$qu->id == $product->qu_id_purchase) selected="selected" @endif value="{{ $qu->id }}">{{ $qu->name }}</option>
 					@endforeach
 				</select>
 				<div class="invalid-feedback">{{ $__t('A quantity unit is required') }}</div>
@@ -416,10 +420,10 @@
 					id="qu_id_consume"
 					name="qu_id_consume">
 					<option></option>
-					@foreach($referencedQuantityunits as $quantityunit)
+					@foreach($quantityunitsReferenced as $qu)
 					<option @if($mode=='edit'
 						&&
-						$quantityunit->id == $product->qu_id_consume) selected="selected" @endif value="{{ $quantityunit->id }}">{{ $quantityunit->name }}</option>
+						$qu->id == $product->qu_id_consume) selected="selected" @endif value="{{ $qu->id }}">{{ $qu->name }}</option>
 					@endforeach
 				</select>
 				<div class="invalid-feedback">{{ $__t('A quantity unit is required') }}</div>
@@ -436,10 +440,10 @@
 					id="qu_id_price"
 					name="qu_id_price">
 					<option></option>
-					@foreach($referencedQuantityunits as $quantityunit)
+					@foreach($quantityunitsReferenced as $qu)
 					<option @if($mode=='edit'
 						&&
-						$quantityunit->id == $product->qu_id_price) selected="selected" @endif value="{{ $quantityunit->id }}">{{ $quantityunit->name }}</option>
+						$qu->id == $product->qu_id_price) selected="selected" @endif value="{{ $qu->id }}">{{ $qu->name }}</option>
 					@endforeach
 				</select>
 				<div class="invalid-feedback">{{ $__t('A quantity unit is required') }}</div>
@@ -762,7 +766,7 @@
 							</td>
 							<td>
 								@if(!empty($barcode->qu_id))
-								{{ FindObjectInArrayByPropertyValue($quantityunits, 'id', $barcode->qu_id)->name }}
+								{{ FindObjectInArrayByPropertyValue($quantityunitsAll, 'id', $barcode->qu_id)->name }}
 								@endif
 							</td>
 							<td>
@@ -886,16 +890,16 @@
 								</a>
 							</td>
 							<td>
-								{{ FindObjectInArrayByPropertyValue($quantityunits, 'id', $quConversion->from_qu_id)->name }}
+								{{ FindObjectInArrayByPropertyValue($quantityunitsAll, 'id', $quConversion->from_qu_id)->name }}
 							</td>
 							<td>
-								{{ FindObjectInArrayByPropertyValue($quantityunits, 'id', $quConversion->to_qu_id)->name }}
+								{{ FindObjectInArrayByPropertyValue($quantityunitsAll, 'id', $quConversion->to_qu_id)->name }}
 							</td>
 							<td>
 								<span class="locale-number locale-number-quantity-amount">{{ $quConversion->factor }}</span>
 							</td>
 							<td class="font-italic">
-								{!! $__t('This means 1 %1$s is the same as %2$s %3$s', FindObjectInArrayByPropertyValue($quantityunits, 'id', $quConversion->from_qu_id)->name, '<span class="locale-number locale-number-quantity-amount">' . $quConversion->factor . '</span>', $__n($quConversion->factor, FindObjectInArrayByPropertyValue($quantityunits, 'id', $quConversion->to_qu_id)->name, FindObjectInArrayByPropertyValue($quantityunits, 'id', $quConversion->to_qu_id)->name_plural, true)) !!}
+								{!! $__t('This means 1 %1$s is the same as %2$s %3$s', FindObjectInArrayByPropertyValue($quantityunitsAll, 'id', $quConversion->from_qu_id)->name, '<span class="locale-number locale-number-quantity-amount">' . $quConversion->factor . '</span>', $__n($quConversion->factor, FindObjectInArrayByPropertyValue($quantityunitsAll, 'id', $quConversion->to_qu_id)->name, FindObjectInArrayByPropertyValue($quantityunitsAll, 'id', $quConversion->to_qu_id)->name_plural, true)) !!}
 							</td>
 						</tr>
 						@endforeach