diff --git a/arrow-data/src/transform/mod.rs b/arrow-data/src/transform/mod.rs
index 340897687d0..7e3f7516d0b 100644
--- a/arrow-data/src/transform/mod.rs
+++ b/arrow-data/src/transform/mod.rs
@@ -509,7 +509,7 @@ impl<'a> MutableArrayData<'a> {
                     MutableArrayData::new(value_child, use_nulls, array_capacity),
                 ]
             }
-            DataType::FixedSizeList(_, _) => {
+            DataType::FixedSizeList(_, size) => {
                 let children = arrays
                     .iter()
                     .map(|array| &array.child_data()[0])
@@ -519,9 +519,9 @@ impl<'a> MutableArrayData<'a> {
                         child_capacities
                             .clone()
                             .map(|c| *c)
-                            .unwrap_or(Capacities::Array(capacity))
+                            .unwrap_or(Capacities::Array(capacity * *size as usize))
                     } else {
-                        Capacities::Array(array_capacity)
+                        Capacities::Array(array_capacity * *size as usize)
                     };
                 vec![MutableArrayData::with_capacities(
                     children, use_nulls, capacities,