diff --git a/src/cal_tools/tools.py b/src/cal_tools/tools.py
index de53ba77e02ca2879d2502299124c8988d91eb3e..314e2084da62ca1355ca24c98332244038c4ff56 100644
--- a/src/cal_tools/tools.py
+++ b/src/cal_tools/tools.py
@@ -1030,3 +1030,17 @@ def write_compressed_frames(
             dataset.id.write_direct_chunk(chunk_start, compressed)
 
     return dataset
+
+
+def reorder_axes(a, from_order, to_order):
+    """Rearrange axes of array a from from_order to to_order
+
+    This does the same as np.transpose(), but making the before & after axes
+    more explicit. from_order is a sequence of strings labelling the axes of a,
+    and to_order is a similar sequence for the axes of the result.
+    """
+    assert len(from_order) == a.ndim
+    assert sorted(from_order) == sorted(to_order)
+    from_order = list(from_order)
+    order = tuple([from_order.index(lbl) for lbl in to_order])
+    return a.transpose(order)
diff --git a/tests/test_cal_tools.py b/tests/test_cal_tools.py
index 36d9d324021b3ce650434d3d651ca1834207b972..5929944c59b1e32836ba7f56387882b328de816f 100644
--- a/tests/test_cal_tools.py
+++ b/tests/test_cal_tools.py
@@ -22,6 +22,7 @@ from cal_tools.tools import (
     recursive_update,
     send_to_db,
     write_constants_fragment,
+    reorder_axes,
 )
 
 # AGIPD operating conditions.
@@ -614,3 +615,13 @@ def test_write_constants_fragment(tmp_path: Path):
                 },
             }
         }
+
+
+def test_reorder_axes():
+    a = np.zeros((10, 32, 256, 3))
+    from_order = ('cells', 'slow_scan', 'fast_scan', 'gain')
+    to_order = ('slow_scan', 'fast_scan', 'cells', 'gain')
+    assert reorder_axes(a, from_order, to_order).shape == (32, 256, 10, 3)
+
+    to_order = ('gain', 'fast_scan', 'slow_scan', 'cells')
+    assert reorder_axes(a, from_order, to_order).shape == (3, 256, 32, 10)