---
title: ES|QL ST_BUFFER function
description:
url: https://www.elastic.co/elastic/docs-builder/docs/2927/reference/query-languages/esql/functions-operators/spatial-functions/st_buffer
products:
- Elasticsearch
---
# ES|QL ST_BUFFER function
- Elastic Cloud Serverless: Preview
- Elastic Stack: Preview since 9.4
## Syntax
## Parameters
Expression of type `geo_point`, `geo_shape`, `cartesian_point` or `cartesian_shape`. If `null`, the function returns `null`.
Buffer distance in the units of the input spatial reference system
(Optional) ST_BUFFER additional options like `quad_segs`, `endcap`, `join` and `mitre_limit`.
## Description
Computes a buffer area around the input geometry at the specified distance. The distance is in the units of the input spatial reference system. Positive distances expand the geometry, negative distances shrink it. A distance of zero will return the input geometry unchanged. Points and lines become polygons when buffered, unless a zero distance is provided.
## Supported types
| geometry | distance | options | result |
|-----------------|----------|---------|-----------------|
| cartesian_point | double | | cartesian_shape |
| cartesian_point | float | | cartesian_shape |
| cartesian_point | integer | | cartesian_shape |
| cartesian_point | long | | cartesian_shape |
| cartesian_shape | double | | cartesian_shape |
| cartesian_shape | float | | cartesian_shape |
| cartesian_shape | integer | | cartesian_shape |
| cartesian_shape | long | | cartesian_shape |
| geo_point | double | | geo_shape |
| geo_point | float | | geo_shape |
| geo_point | integer | | geo_shape |
| geo_point | long | | geo_shape |
| geo_shape | double | | geo_shape |
| geo_shape | float | | geo_shape |
| geo_shape | integer | | geo_shape |
| geo_shape | long | | geo_shape |
### Supported function named parameters
(integer) Number of line segments used to approximate a quarter circle. Defaults to 8.
(keyword) End cap style for buffering linear geometries. Defaults to round.
(keyword) Join style for buffering. Defaults to round.
(double) Mitre ratio limit, only meaningful when join=mitre. Defaults to 5.0.
## Examples
```esql
ROW wkt = "POLYGON ((0 0, 4 0, 4 4, 0 4, 0 0))"
| EVAL buffered = ST_BUFFER(TO_GEOSHAPE(wkt), -1)
```
| wkt:keyword | buffered:geo_shape |
|-------------------------------------|---------------------------------------------------------|
| POLYGON ((0 0, 4 0, 4 4, 0 4, 0 0)) | POLYGON ((1.0 1.0, 1.0 3.0, 3.0 3.0, 3.0 1.0, 1.0 1.0)) |
The optional `options` argument can configure end caps and join styles. Combining `endcap=flat` with `join=mitre` produces sharp corners on a buffered L-shape:
```esql
ROW geom = TO_CARTESIANSHAPE("LINESTRING(0 0, 10 0, 10 10)")
| EVAL buffered = ST_BUFFER(geom, 2, {"endcap": "flat", "join": "mitre"})
| KEEP buffered
```
| buffered:cartesian_shape |
|---------------------------------------------------------------------------------|
| POLYGON ((8.0 2.0, 8.0 10.0, 12.0 10.0, 12.0 -2.0, 0.0 -2.0, 0.0 2.0, 8.0 2.0)) |
### Diagrams
**Negative distance shrinks a polygon**
Buffering a 10x10 square by `-2` produces a smaller square inset by 2 units on each side.
**Buffering a point produces a circle**
A point with positive distance becomes a polygon approximating a circle (8 segments per quadrant by default).
**Default round end caps on a line**
A line buffered with default options has rounded end caps (`endcap=round`).
**Flat end caps on a line**
Setting `endcap=flat` keeps the buffer flush with the line's endpoints.
**Square end caps on a line**
`endcap=square` extends the buffer past each endpoint by the buffer distance.
**Mitre joins on a buffered corner**
`join=mitre` produces sharp corners. Combined with `endcap=flat` you get a clean rectangle for a buffered L-shape.
