diff --git a/InvenTree/InvenTree/validators.py b/InvenTree/InvenTree/validators.py
index f3fd9ef306..0e1622a49a 100644
--- a/InvenTree/InvenTree/validators.py
+++ b/InvenTree/InvenTree/validators.py
@@ -7,9 +7,56 @@ from django.utils.translation import gettext_lazy as _
 
 
 def validate_part_name(value):
-    # Prevent some illegal characters in part names
-    for c in ['|', '#', '$']:
+    """ Prevent some illegal characters in part names.
+    """
+
+    for c in ['|', '#', '$', '{', '}']:
         if c in str(value):
             raise ValidationError(
                 _('Invalid character in part name')
             )
+
+
+def validate_overage(value):
+    """ Validate that a BOM overage string is properly formatted.
+
+    An overage string can look like:
+
+    - An integer number ('1' / 3 / 4)
+    - A percentage ('5%' / '10 %')
+    """
+
+    value = str(value).lower().strip()
+
+    # First look for a simple integer value
+    try:
+        i = int(value)
+
+        if i < 0:
+            raise ValidationError(_("Overage value must not be negative"))
+        
+        # Looks like an integer!
+        return True
+    except ValueError:
+        pass
+
+    # Now look for a percentage value
+    if value.endswith('%'):
+        v = value[:-1].strip()
+
+        # Does it look like a number?
+        try:
+            f = float(v)
+
+            if f < 0:
+                raise ValidationError(_("Overage value must not be negative"))
+            elif f > 100:
+                raise ValidationError(_("Overage must not exceed 100%"))
+
+            return True
+        except ValueError:
+            pass
+
+    raise ValidationError(
+        _("Overage must be an integer value or a percentage")
+    )
diff --git a/InvenTree/part/forms.py b/InvenTree/part/forms.py
index 88c6c11385..d4e70ee47a 100644
--- a/InvenTree/part/forms.py
+++ b/InvenTree/part/forms.py
@@ -133,6 +133,7 @@ class EditBomItemForm(HelperForm):
             'part',
             'sub_part',
             'quantity',
+            'overage',
             'note'
         ]
 
diff --git a/InvenTree/part/migrations/0025_auto_20190515_0012.py b/InvenTree/part/migrations/0025_auto_20190515_0012.py
new file mode 100644
index 0000000000..aaeb8ea1a3
--- /dev/null
+++ b/InvenTree/part/migrations/0025_auto_20190515_0012.py
@@ -0,0 +1,46 @@
+# Generated by Django 2.2 on 2019-05-14 14:12
+
+import InvenTree.validators
+import django.core.validators
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('part', '0024_partcategory_default_keywords'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='bomitem',
+            name='overage',
+            field=models.CharField(blank=True, help_text='Estimated build wastage quantity (absolute or percentage)', max_length=24, validators=[InvenTree.validators.validate_overage]),
+        ),
+        migrations.AlterField(
+            model_name='bomitem',
+            name='note',
+            field=models.CharField(blank=True, help_text='BOM item notes', max_length=100),
+        ),
+        migrations.AlterField(
+            model_name='bomitem',
+            name='part',
+            field=models.ForeignKey(help_text='Select parent part', limit_choices_to={'active': True, 'buildable': True}, on_delete=django.db.models.deletion.CASCADE, related_name='bom_items', to='part.Part'),
+        ),
+        migrations.AlterField(
+            model_name='bomitem',
+            name='quantity',
+            field=models.PositiveIntegerField(default=1, help_text='BOM quantity for this BOM item', validators=[django.core.validators.MinValueValidator(0)]),
+        ),
+        migrations.AlterField(
+            model_name='bomitem',
+            name='sub_part',
+            field=models.ForeignKey(help_text='Select part to be used in BOM', limit_choices_to={'active': True, 'consumable': True}, on_delete=django.db.models.deletion.CASCADE, related_name='used_in', to='part.Part'),
+        ),
+        migrations.AlterField(
+            model_name='supplierpart',
+            name='URL',
+            field=models.URLField(blank=True, help_text='URL for external supplier part link'),
+        ),
+    ]
diff --git a/InvenTree/part/models.py b/InvenTree/part/models.py
index d255a319f3..b316da2813 100644
--- a/InvenTree/part/models.py
+++ b/InvenTree/part/models.py
@@ -661,6 +661,7 @@ class BomItem(models.Model):
         part: Link to the parent part (the part that will be produced)
         sub_part: Link to the child part (the part that will be consumed)
         quantity: Number of 'sub_parts' consumed to produce one 'part'
+        overage: Estimated losses for a Build. Can be expressed as absolute value (e.g. '7') or a percentage (e.g. '2%')
         note: Note field for this BOM item
     """
 
@@ -688,6 +689,10 @@ class BomItem(models.Model):
     # Quantity required
     quantity = models.PositiveIntegerField(default=1, validators=[MinValueValidator(0)], help_text='BOM quantity for this BOM item')
 
+    overage = models.CharField(max_length=24, blank=True, validators=[validators.validate_overage],
+                               help_text='Estimated build wastage quantity (absolute or percentage)'
+                               )
+
     # Note attached to this BOM line item
     note = models.CharField(max_length=100, blank=True, help_text='BOM item notes')