---
title: "LayerMetrics"
description: "Per-layer DFM comparison metrics between designed and predicted geometry."
canonical_url: "https://www.rosette.dev/docs/api-reference/LayerMetrics"
markdown_url: "https://www.rosette.dev/docs/api-reference/LayerMetrics.md"
source_url: "https://github.com/PreFab-Photonics/rosette/blob/f086d7670645fd36c05362d696d442a2b2e74850/www/content/docs/api-reference/LayerMetrics.mdx"
docs_channel: "main"
docs_revision: "f086d7670645fd36c05362d696d442a2b2e74850"
---

# LayerMetrics

Per-layer DFM comparison metrics between designed and predicted geometry.

Import with `from rosette.dfm import LayerMetrics`.

Available on each `LayerPrediction` in a `DfmResult`. Provides quantitative
measures of how the predicted (post-fabrication) geometry differs from the
designed geometry.

```python
result = run_dfm(cell, layers=[Layer(1)])
for lp in result.layers:
    m = lp.metrics
    if m:
        print(f"Layer {m.layer}: edge dev {m.max_edge_deviation:.3f} um, "
              f"area dev {m.area_deviation:.1%}")
```

## Attributes



### `layer`

```python
layer: tuple[int, int]
```

The `(number, datatype)` of the layer.





### `max_edge_deviation`

```python
max_edge_deviation: float
```

Maximum edge deviation between designed and predicted geometry, in design units.





### `area_deviation`

```python
area_deviation: float
```

Relative area change (signed). Negative values indicate shrinkage,
positive values indicate expansion.





### `designed_area`

```python
designed_area: float
```

Designed area in design units squared.





### `predicted_area`

```python
predicted_area: float
```

Predicted area in design units squared.





### `designed_feature_count`

```python
designed_feature_count: int
```

Number of connected components in the designed raster.





### `predicted_feature_count`

```python
predicted_feature_count: int
```

Number of connected components in the predicted raster.