diff --git a/CHANGELOG.md b/CHANGELOG.md
index 522e4979..7ea6fe53 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,20 @@ those changes.
 
 ## [Unreleased]
 
+## [1.82.0] - 2026-09-07
+
+### Added
+
+- `score_plot(sizes=...)`: a value per observation, whose **area** the marker
+  then carries, so a score plot can answer two questions at once (which batches
+  are extreme along the components, and how far each sits off them). Area, not
+  diameter, is proportional to the value, and one scale is shared by the plain
+  and the highlighted traces, so a highlighted point keeps its own area rather
+  than being enlarged. `settings["size_max"]` sets the diameter of the largest
+  marker and `size_name` names the value in the hover text. A negative value, a
+  series that does not cover every observation, or an all-zero series raises
+  rather than drawing a plot that cannot be read.
+
 ## [1.81.2] - 2026-09-07
 
 ### Fixed
@@ -4284,7 +4298,8 @@ this entry records them together.
 - Reworked the README with a sharper value proposition and a
   "Why not scikit-learn?" comparison table.
 
-[Unreleased]: https://github.com/kgdunn/process-improve/compare/v1.81.2...HEAD
+[Unreleased]: https://github.com/kgdunn/process-improve/compare/v1.82.0...HEAD
+[1.82.0]: https://github.com/kgdunn/process-improve/compare/v1.81.2...v1.82.0
 [1.81.2]: https://github.com/kgdunn/process-improve/compare/v1.81.1...v1.81.2
 [1.81.1]: https://github.com/kgdunn/process-improve/compare/v1.81.0...v1.81.1
 [1.81.0]: https://github.com/kgdunn/process-improve/compare/v1.80.0...v1.81.0
diff --git a/CITATION.cff b/CITATION.cff
index a6a8abf2..e43fef37 100644
--- a/CITATION.cff
+++ b/CITATION.cff
@@ -12,7 +12,7 @@ authors:
 repository-code: "https://github.com/kgdunn/process-improve"
 url: "https://kgdunn.github.io/process-improve/"
 license: MIT
-version: 1.81.2
+version: 1.82.0
 date-released: "2026-09-07"
 keywords:
   - chemometrics
diff --git a/pyproject.toml b/pyproject.toml
index fda2fbcc..f713c6bf 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "process-improve"
-version = "1.81.2"
+version = "1.82.0"
 description = 'Designed Experiments; Latent Variables (PCA, PLS, multivariate methods with missing data); Process Monitoring; Batch data analysis.'
 readme = "README.md"
 license = "MIT"
diff --git a/src/process_improve/multivariate/plots.py b/src/process_improve/multivariate/plots.py
index 17b0f609..861618ee 100644
--- a/src/process_improve/multivariate/plots.py
+++ b/src/process_improve/multivariate/plots.py
@@ -81,6 +81,48 @@ def plot_pre_checks(model: BaseEstimator, pc_horiz: int, pc_vert: int, pc_depth:
     return True
 
 
+def _area_scale(sizes: pd.Series | None, index: pd.Index, size_max: float) -> dict:
+    """Return the Plotly keys that make a marker's area, not its diameter, proportional to ``sizes``.
+
+    One ``sizeref`` is computed for the whole series and shared by every trace, so that a
+    highlighted point and a plain one of the same value are drawn the same size. Values that
+    cannot be an area, or that do not cover the observations being plotted, raise instead.
+    """
+    if sizes is None:
+        return {}
+    values = pd.Series(sizes).reindex(index).astype(float)
+    if values.isna().any():
+        msg = f"`sizes` has no value for these observations: {list(values.index[values.isna()])[:5]}"
+        raise ValueError(msg)
+    if (values < 0).any():
+        msg = "`sizes` cannot be negative: the marker area is proportional to it."
+        raise ValueError(msg)
+    largest = float(values.max())
+    if largest <= 0:
+        msg = "`sizes` must have at least one positive value to set the marker scale."
+        raise ValueError(msg)
+    return {"sizemode": "area", "sizeref": 2.0 * largest / size_max**2, "sizemin": 2}
+
+
+def _sized_marker(styling: dict, index: list, sizes: pd.Series | None, marker_area: dict) -> dict:
+    """Return the marker specification for one trace, with its area carrying ``sizes`` when given."""
+    if sizes is None:
+        return styling
+    return {**styling, "size": pd.Series(sizes).reindex(index).astype(float).to_numpy(), **marker_area}
+
+
+def _size_hover(index: list, sizes: pd.Series | None, size_name: str) -> dict:
+    """Return hover text reporting the value the marker area stands for, so it can be read exactly."""
+    if sizes is None:
+        return {}
+    values = pd.Series(sizes).reindex(index).astype(float)
+    label = size_name or "size"
+    return {
+        "customdata": values.to_numpy(),
+        "hovertemplate": "%{text}<br>" + label + ": %{customdata:.4g}<extra></extra>",
+    }
+
+
 def score_plot(  # noqa: C901, PLR0913
     model: BaseEstimator,
     pc_horiz: int = 1,
@@ -89,6 +131,9 @@ def score_plot(  # noqa: C901, PLR0913
     items_to_highlight: dict[str, list] | None = None,
     settings: dict | None = None,
     fig: go.Figure | None = None,
+    *,
+    sizes: pd.Series | None = None,
+    size_name: str = "",
 ) -> go.Figure:
     """Generate a 2D or 3D score plot for the given latent variable model.
 
@@ -114,6 +159,17 @@ def score_plot(  # noqa: C901, PLR0913
 
         will highlight the items in ``items_in_red`` with the given colour and shape.
 
+    sizes : pd.Series, optional
+        One non-negative value per observation, indexed as the scores are. The marker
+        **area** is made proportional to it, so that a marker of twice the area stands for
+        twice the value, and the largest value is drawn ``settings["size_max"]`` pixels
+        across. The plain and the highlighted traces share one scale, and a highlighted
+        point keeps its own area rather than being enlarged, because two meanings on one
+        channel cannot both be read. Give the reader that scale as well: an area cannot be
+        read off a plot on its own.
+    size_name : str, optional
+        What ``sizes`` measures, for example ``"SPE"``; it names the value in the hover text.
+
     settings : dict
         Default settings::
 
@@ -128,6 +184,8 @@ def score_plot(  # noqa: C901, PLR0913
                                                # (pc_depth > 0).
                 "show_labels": False,          # bool: add a label for each observation
                 "show_legend": True,           # bool: show clickable legend
+                "size_max": 26,                # float: diameter in pixels of the
+                                               # largest marker, when `sizes` is given
                 "html_image_height": 500,      # int: image height in pixels
                 "html_aspect_ratio_w_over_h": 16/9,  # float: width as ratio of height
                 "template": "pi_journal",        # str: registered Plotly theme name
@@ -167,11 +225,13 @@ def check_ellipse_conf_level(cls, val: float) -> float:
         )
         show_labels: bool = False
         show_legend: bool = True
+        size_max: float = 26.0
         html_image_height: float = 500.0
         html_aspect_ratio_w_over_h: float = 16 / 9.0
         template: str = DEFAULT_THEME
 
     setdict = Settings(**settings).model_dump() if settings else Settings().model_dump()
+    marker_area = _area_scale(sizes, data_to_plot.index, setdict["size_max"])
     if fig is None:
         fig = go.Figure()
 
@@ -198,11 +258,10 @@ def check_ellipse_conf_level(cls, val: float) -> float:
                 z=data_to_plot.loc[default_index, pc_depth],
                 name=name,
                 mode="markers+text" if setdict["show_labels"] else "markers",
-                marker=dict(
-                    symbol="circle",
-                ),
+                marker=_sized_marker({"symbol": "circle"}, default_index, sizes, marker_area),
                 text=list(default_index),
                 textposition="top center",
+                **_size_hover(default_index, sizes, size_name),
             )
         )
         # Items to highlight, if any
@@ -215,9 +274,10 @@ def check_ellipse_conf_level(cls, val: float) -> float:
                     z=data_to_plot.loc[index, pc_depth],
                     name=name,
                     mode="markers+text" if setdict["show_labels"] else "markers",
-                    marker=styling,
+                    marker=_sized_marker(styling, index, sizes, marker_area),
                     text=list(index),
                     textposition="top center",
+                    **_size_hover(index, sizes, size_name),
                 )
             )
     else:
@@ -228,12 +288,10 @@ def check_ellipse_conf_level(cls, val: float) -> float:
                 y=data_to_plot.loc[default_index, pc_vert],
                 name=name,
                 mode="markers+text" if setdict["show_labels"] else "markers",
-                marker=dict(
-                    symbol="circle",
-                    size=7,
-                ),
+                marker=_sized_marker({"symbol": "circle", "size": 7}, default_index, sizes, marker_area),
                 text=default_index,
                 textposition="top center",
+                **_size_hover(default_index, sizes, size_name),
             )
         )
         # Items to highlight, if any
@@ -245,9 +303,10 @@ def check_ellipse_conf_level(cls, val: float) -> float:
                     y=data_to_plot.loc[index, pc_vert],
                     name=name,
                     mode="markers+text" if setdict["show_labels"] else "markers",
-                    marker=styling,
+                    marker=_sized_marker(styling, index, sizes, marker_area),
                     text=list(index),
                     textposition="top center",
+                    **_size_hover(index, sizes, size_name),
                 )
             )
         if setdict["show_ellipse"]:
diff --git a/tests/test_multivariate.py b/tests/test_multivariate.py
index 8d2de8cc..e2c9623c 100644
--- a/tests/test_multivariate.py
+++ b/tests/test_multivariate.py
@@ -4581,6 +4581,44 @@ def test_score_plot_basic(fixture_pca_for_plots: PCA) -> None:
     assert len(fig.data) >= 1  # at least the scores trace
 
 
+def test_score_plot_sizes_area_encoding(fixture_pca_for_plots: PCA) -> None:
+    """`sizes` puts the value on the marker area, on one scale shared by every trace."""
+    model = fixture_pca_for_plots
+    spe = model.spe_.iloc[:, -1]
+    plain = model.score_plot()
+    assert plain.data[0].marker.sizemode is None  # the default path is untouched
+    assert plain.data[0].marker.size == 7
+
+    fig = model.score_plot(sizes=spe, size_name="SPE")
+    marker = fig.data[0].marker
+    assert marker.sizemode == "area"
+    assert marker.size == pytest.approx(spe.to_numpy())
+    # sizeref is what turns a value into an area: the largest value fills `size_max` pixels.
+    assert marker.sizeref == pytest.approx(2.0 * spe.max() / 26.0**2)
+    assert "SPE" in fig.data[0].hovertemplate
+
+    highlighted = model.score_plot(
+        items_to_highlight={'{"color": "red"}': list(spe.index[:2])}, sizes=spe, size_name="SPE"
+    )
+    refs = {trace.marker.sizeref for trace in highlighted.data if trace.marker.sizeref is not None}
+    assert len(refs) == 1, "the highlighted trace must be read on the same scale as the rest"
+
+
+def test_score_plot_sizes_settings_and_guards(fixture_pca_for_plots: PCA) -> None:
+    """`size_max` sets the largest marker, and a value that cannot be an area is refused."""
+    model = fixture_pca_for_plots
+    spe = model.spe_.iloc[:, -1]
+    fig = model.score_plot(sizes=spe, settings={"size_max": 40})
+    assert fig.data[0].marker.sizeref == pytest.approx(2.0 * spe.max() / 40.0**2)
+
+    with pytest.raises(ValueError, match="cannot be negative"):
+        model.score_plot(sizes=-spe)
+    with pytest.raises(ValueError, match="no value for these observations"):
+        model.score_plot(sizes=spe.iloc[:3])
+    with pytest.raises(ValueError, match="at least one positive value"):
+        model.score_plot(sizes=spe * 0.0)
+
+
 def test_score_plot_with_ellipse(fixture_pca_for_plots: PCA) -> None:
     """score_plot with ellipse should have an extra trace for the ellipse."""
     fig = fixture_pca_for_plots.score_plot(settings={"show_ellipse": True})