diff --git a/conservancy_beancount/reports/core.py b/conservancy_beancount/reports/core.py
index cf381254bb8f7735a47b90b01155c7110c1327de..5ded97fbd1b84a474817f64c0fa1469ea21543a1 100644
--- a/conservancy_beancount/reports/core.py
+++ b/conservancy_beancount/reports/core.py
@@ -199,6 +199,16 @@ class RelatedPostings(Sequence[data.Posting]):
         except NameError:
             return Balance()
 
+    def balance_at_cost(self) -> Balance:
+        balance = MutableBalance()
+        for post in self:
+            if post.cost is None:
+                balance.add_amount(post.units)
+            else:
+                number = post.units.number * post.cost.number
+                balance.add_amount(data.Amount(number, post.cost.currency))
+        return balance
+
     def meta_values(self,
                     key: MetaKey,
                     default: Optional[MetaValue]=None,