--- title: "How to size points by a number" description: "Size each point marker from a numeric field to make a proportional-symbol (bubble) map. Set the minimum and maximum size on the Style tab. Point layers only." sidebar: label: "Size points by a number" --- A numeric field sizes each marker from its value. Small values make small markers; large values make large markers. Open a point layer's `Style` tab, switch `Size markers by` from `Uniform size` to a numeric field, and set the minimum and maximum marker size. Click `Save` to apply. **[See it on an example map](https://mangomap-staging.com/examples-staging/maps/042tb3tl/world-point-styling-lab)** Open the World Point Styling Lab. `Centroids — Bubble` is on when the map opens. Each country point is sized by population. Large countries have large circles. The `Two Fields` folder adds colour from a second field (`Centroids — Continent and Population`, `Centroids — GDP and Population`) and a size range that scales with zoom (`Major Cities — Population, Zoom Scaled`). ## Before you start - The layer must be a **point** layer with at least one numeric attribute. Lines and polygons have no size driver. If a point layer has no numeric field, the `Size markers by` dropdown offers only `Uniform size`. - You need edit access to the map. - Marker type matters: sizing applies to `Circle`, `Icon`, and `Custom Icon` markers, but the `Size markers by` control is only visible while `Circle` or `Icon` is selected. Using a custom icon? Pick the size field first, then switch the marker to `Custom Icon` — the sizing stays applied. Sizing doesn't apply to `Heatmap` (a different visualization). ## Open the Style tab In the layer panel, select your point layer. Click the `Style` tab. ## Switch "Size markers by" to a numeric field Below the `Colour markers by` driver, find `Size markers by`. It defaults to `Uniform size`. Open it and pick the numeric field whose values should drive marker size. Only numeric fields appear in the list. The single size slider is replaced by a **minimum / maximum size range**. ## Set the minimum and maximum size Two inputs — `Minimum size` and `Maximum size`, each in pixels — with a dual-handle slider set the size range: - The smallest value in the field renders at the minimum size; the largest at the maximum. - Range: 2–60 px. Defaults: minimum `4` px → maximum `20` px. The two values stay at least 4 px apart. Style section of the Centroids — Bubble layer with Marker type Circle, Colour markers by Single colour, and Size markers by set to pop_est; the size row reads 4 px to 20 px and ends with the Vary size by zoom level button Widen the gap to increase contrast; narrow it to keep sizes closer. ## (Optional) Scale the sizes as viewers zoom On `Circle` markers, click the `Vary size by zoom level` button next to the size range. Each zoom stop then holds a `Scale` that multiplies both the minimum and maximum size at that zoom. The ratio between small and large markers stays the same at every zoom. See [How to vary marker size by zoom level](/docs/styling-layers/vary-marker-size-by-zoom) for the stop controls. ## (Optional) Combine size with a colour driver The size driver is independent of the colour driver, so you can encode two variables at once (see [How to colour and size points by two fields](/docs/styling-layers/colour-and-size-points-by-two-fields)): - **Single colour + size** — a plain proportional-symbol map: one colour, varying size. The legend shows a size key — a set of min / median / max circles for the field. The caption under the key is the field's alias from the `Format` tab, or the field name if there's no alias. The key's numbers use the field's `Format` settings. - **Quantity colour + size** — colour by one numeric field and size by another. The legend shows the colour breaks with the size key below them. - **Category colour + size** — colour each category and size by a numeric field. The legend shows the category swatches with the same size key below them. - **Colour by zoom + size** — `Circle` markers change colour as viewers zoom and take their size from the field. See [How to change marker colour by zoom level](/docs/styling-layers/colour-markers-by-zoom). ## Save Click `Save` at the bottom of the panel. The map redraws with markers sized by the field. World Point Styling Lab in the map viewer: Centroids — Bubble draws country points sized by population, and the Legend shows its size key with 1,397,715,000, 698,857,570, and 140 If the map doesn't update, you probably didn't click `Save` — see [Troubleshooting: my style change isn't appearing on the map](/docs/styling-layers/troubleshoot-style-not-applying). ## If the markers are all nearly the same size The field's values may be tightly clustered, or an outlier may be stretching the range so most features land near the minimum. Widen the min/max gap, or pre-process the field (for example, log-scale very skewed data) before import. ## If you want a fixed size per category or break instead Field-driven sizing changes smoothly across the range. For a _fixed_ size per category or per class break (not a smooth range), leave `Size markers by` on `Uniform size` and set a per-row marker size in the per-category / per-break customisation panel — see [How to customise category and class break symbology](/docs/styling-layers/customise-category-and-class-break-symbology). ## Related - [Point layer style controls](/docs/styling-layers/point-style-reference) — the `Size markers by` driver, its ranges and defaults. - [How to set a uniform style on a point layer](/docs/styling-layers/set-a-uniform-point-style) - [How to vary marker size by zoom level](/docs/styling-layers/vary-marker-size-by-zoom) — make markers grow or shrink as viewers zoom. - [How to style features by quantity](/docs/styling-layers/style-by-quantity) — colour (rather than size) driven by a numeric field. - [How to style features by category](/docs/styling-layers/style-by-category) - [How to make a heatmap from a point layer](/docs/styling-layers/make-a-heatmap) — the other way to read point magnitude / density quickly. - [How layer styling works in MangoMap](/docs/styling-layers/concepts-layer-styling)