diff --git a/src/depiction/image/multi_channel_image.py b/src/depiction/image/multi_channel_image.py
index 1d3f844..4dbe135 100644
--- a/src/depiction/image/multi_channel_image.py
+++ b/src/depiction/image/multi_channel_image.py
@@ -43,6 +43,12 @@ def n_channels(self) -> int:
         """Number of channels."""
         return self._data.sizes["c"]
 
+    @property
+    def n_nonzero(self) -> int:
+        """Number of non-zero values."""
+        # TODO efficient impl
+        return (~self.bg_mask).sum().item()
+
     # TODO sparse_values, sparse_coordinates - these are currently widely used which i guess is a problem
 
     @property
diff --git a/tests/unit/image/test_multi_channel_image.py b/tests/unit/image/test_multi_channel_image.py
index d064a10..516c12e 100644
--- a/tests/unit/image/test_multi_channel_image.py
+++ b/tests/unit/image/test_multi_channel_image.py
@@ -44,6 +44,15 @@ def test_n_channels(mock_image: MultiChannelImage) -> None:
     assert mock_image.n_channels == 1
 
 
+def test_n_nonzero(mock_image: MultiChannelImage) -> None:
+    assert mock_image.n_nonzero == 6
+
+
+def test_n_nonzero_when_sparse(mock_image: MultiChannelImage) -> None:
+    mock_image.data_spatial[1, 0, 0] = 0
+    assert mock_image.n_nonzero == 5
+
+
 def test_dtype(mock_image: MultiChannelImage) -> None:
     assert mock_image.dtype == float