diff --git a/shared/src/orisys_app_shared/record/experiment.py b/shared/src/orisys_app_shared/record/experiment.py
index fc0769b..8b90b5c 100644
--- a/shared/src/orisys_app_shared/record/experiment.py
+++ b/shared/src/orisys_app_shared/record/experiment.py
@@ -77,6 +77,7 @@ FORCES_HEADER = (
     "FN_output_N",
     "FX_output_N",
     "FY_output_N",
+    "Fmag_raw",
 )
 FRAMES_HEADER = (
     "frame_id",
@@ -109,6 +110,14 @@ ROW_BACKLOG = 8192
 VIDEO_PACING_TOLERANCE = 0.5
 
 
+def raw_magnitude(fn: float, fx: float, fy: float) -> float:
+    """Magnitude of the three raw force components. Missing any one leaves it blank."""
+    values = (fn, fx, fy)
+    if not all(np.isfinite(value) for value in values):
+        return float("nan")
+    return float(np.sqrt(sum(value * value for value in values)))
+
+
 def format_value(value: float) -> str:
     """Full-precision CSV cell. ``NaN`` means "not available" and is left empty.
 
@@ -1142,6 +1151,7 @@ class _SessionWriter:
                 format_value(sample.fn_n_processed),
                 format_value(sample.fx_n_processed),
                 format_value(sample.fy_n_processed),
+                format_value(raw_magnitude(sample.fn_raw, sample.fx_raw, sample.fy_raw)),
             )
         )
 
diff --git a/shared/tests/test_experiment_recorder.py b/shared/tests/test_experiment_recorder.py
index 7bf1b42..5324c91 100644
--- a/shared/tests/test_experiment_recorder.py
+++ b/shared/tests/test_experiment_recorder.py
@@ -118,11 +118,15 @@ def test_unavailable_values_are_empty_not_zero(root):
 
     failed = rows[1]
     assert failed["valid"] == "0"
-    for column in ("FN_raw", "FX_raw", "FY_raw", "FN_N", "FX_N", "FY_N"):
+    for column in ("FN_raw", "FX_raw", "FY_raw", "FN_N", "FX_N", "FY_N", "Fmag_raw"):
         assert failed[column] == "", "a failed readout was written as a number"
 
+    recorded = rows[0]
+    assert recorded["Fmag_raw"] == repr((9.0 ** 2 + 0.4 ** 2 + 0.4 ** 2) ** 0.5)
+
     no_raw = rows[2]
     assert no_raw["FN_raw"] == "" and no_raw["FX_raw"] == "", "raw was not left empty"
+    assert no_raw["Fmag_raw"] == ""
     assert no_raw["FN_N"] == "2.0", "calibrated values must still be recorded"
     assert no_raw["valid"] == "1"