Contour Map Generator: Contour Lines for Any Place, at Your Interval

What a Contour Map Shows

A contour line joins points of equal height. Draw them at a fixed step, the contour interval, and a flat map starts to show hills and valleys. Close lines mean a steep slope, wide gaps mean gentle ground, and closed loops mark hilltops or hollows. Every topographic map, from hiking maps to building plans, uses them.

What This Contour Map Tool Does

This contour map creator needs only two choices from you: a centre point and a square of 1 to 5 km² around it. The tool loads the terrain tiles that cover the square, turns their colours into heights, cleans and smooths them, and traces a contour line at every level of your interval. About 12 seconds later the lines appear on the map, and they are made again each time you change the centre, the area, the interval, the units or the smoothing. Everything is computed in your browser.

Free to Use and Free to Download, With No Sign-Up

You can use this contour map generator free online, and every file is a free download: there is no account, email or payment. The terrain tiles come straight from a public dataset, the contours and the PDF are made on your device, and a share link holds only the centre, the area and your settings. If you searched for a contour map generator free download, there is nothing to install: the tool runs in your browser on any computer or phone.

Choosing the Place and the Area

Click the map to set the centre of the area, search for a town, an address or a mountain, press My location, or load one of the examples. A red dot marks the centre and a dashed square shows the area that will be mapped. Drag the red dot to move the area. The Area slider sets the size from 1 km² (1 × 1 km, the default) to 5 km² (about 2.24 × 2.24 km) in steps of 0.5 km²: use 1 km² for a plot or a village and the larger squares for a whole hill or valley.

Setting the Contour Interval

Type any interval in the Contour interval box, press one of the preset buttons below it, or press Auto. Auto divides the relief of the area by 22 and rounds up to the next common interval, which gives up to 22 levels (see the tables below). The m and ft buttons switch all heights, the interval and the downloads between metres and feet. If an interval would draw more than 250 levels, the tool doubles it until the map stays readable, and says so.

Smoothing, Colour Fill and Labels

Smoothing calms small bumps in the data: Light is the default, Strong gives round lines for presentations, and Off keeps every detail. Colour fill tints the square from green (low) to brown (high), and Height labels writes the height on the index contours. Hover over any line to see its height. The map styles are Terrain, Street, Satellite and Plain; Plain shows the contours alone on a light background.

Reading the Figures, the Drawing and the Chart

The yellow box describes the ground in words (flat, gently rolling, hilly, steep hills or mountainous), with its relief. The cards give the centre elevation, the lowest and the highest point, the relief, the mean elevation over the area, the mean slope with the share of the area steeper than 30%, the steepest slope and the number and length of the lines. The contour drawing shows the same lines on a white page with a north arrow, a scale bar and a height legend, and the bar chart shows how much of the area lies at each height. The Contour levels table lists every level.

Downloads, Sharing and the PDF Report

If you need a contour map generator with GeoJSON output, GeoJSON saves the lines in latitude and longitude with their height, for QGIS, ArcGIS and web maps. KML opens in Google Earth. For CAD users, this is a free contour map generator online with a CAD export: DXF (CAD) saves 3D polylines on the layers CONTOUR and INDEX, in metres (or feet) east and north of the centre, with the height as Z. Copy share link copies a link that opens the same place and settings, and Download PDF report saves a report with the maplity.com letterhead and watermark, the figures, the height chart, the contour drawing, the levels table and the method.

Spacing Shows the Slope

The closer the lines, the steeper the ground. With a 10 m interval, lines 10 m apart on the ground mean a slope of 100% (45°), and lines 100 m apart mean 10%. Evenly spaced lines mean an even slope; lines that get closer towards the top mean a slope that steepens (a convex hill), and lines that get closer towards the bottom mean a slope that eases off (a concave hill).

Shapes Show the Landforms

Where contour lines bend into a V or a U, the point of the V shows the direction of the landform. In a valley or a stream bed the V points uphill; on a ridge or a spur it points downhill. Small closed loops mark hilltops, or hollows when the heights go down towards the middle. A saddle, the low point on a ridge between two tops, looks like two sets of loops facing each other.

Rules That Always Hold

Contour lines never cross or split, because one place cannot have two heights. They only touch where there is a vertical cliff. Every line closes on itself somewhere, even if that is outside the map. Water flows at right angles to the lines, from higher to lower ones.

Choosing a Contour Interval

A good contour map has 10 to 30 lines across the area. Fewer lines hide the shape of the land; more lines crowd together on steep slopes. The Auto button follows one simple rule: it divides the relief (the highest point minus the lowest, as shown) by 22 and rounds up to the next common interval. The tables below are made from that rule, so they match what the tool and the 200-place tables show.

Terrain types use the relief in metres: flat under 10 m, gently rolling 10 to 49 m, hilly 50 to 149 m, steep hills 150 to 399 m and mountainous from 400 m. You can always type your own interval: 0.5 m (or 1 ft) for drainage on flat ground where the data is detailed, for example in parts of the USA, or a round 10 m or 20 m to match a printed map.

1. Site plans and building design

Architects and home builders need the shape of a plot before they place a house, a driveway or a retaining wall. A contour map with a 0.5 or 1 m interval shows which way the land falls and how much, and the DXF file drops straight into a CAD drawing as a first base layer.

2. Landscaping and garden design

Terraces, paths, ponds and lawns all depend on the fall of the land. Contour lines show where water will run, where a level area would need the most digging, and where a path can follow the slope gently.

3. Farming, drainage and keyline design

Farmers use contours to plan drainage, terraces and contour ploughing, which follows the lines to slow water and keep soil in place. Keyline and permaculture designs start from a good contour map of the land.

4. Hiking, orienteering and outdoor planning

Walkers and orienteers read contour lines to find valleys, ridges, cliffs and the easiest way up a hill. A contour map of a camp site, a climb or a crossing adds detail that small-scale maps leave out.

5. Roads, paths and earthworks

At the early stage of a project, engineers look at contour maps to set the line of a road or a path, estimate cut and fill, and find where slopes are too steep. The steepest slope and the relief figures give a quick first check.

6. Flood and water studies

Contour lines show the low ground where water gathers and the direction it flows. A map around a house, a river bend or a low field helps to see which areas sit only a metre or two above the water.

7. Solar farms and wind sites

Ground-mounted solar panels are cheapest on gentle, south-facing slopes, and wind turbines like exposed high ground. A contour map with the slope figures helps to screen a site before a detailed survey.

8. Geography teaching and learning

Contour maps are a core skill in geography and geology. Students can make a map of a volcano, a glacial valley or their own town, and learn to see hills, valleys, saddles and cliffs in the pattern of the lines.

9. Real estate and land buying

Two plots of the same size can be very different to build on. A contour map shows whether land is flat, gently sloping or steep, which affects the cost of foundations, access and drainage.

10. Maps, games and art

Designers use real contour lines for posters, laser-cut models, 3D printing, game levels and wall art. The clean SVG-style drawing in the PDF and the GeoJSON lines are easy to style in other programs.

1. Finding the Tiles: Web Mercator

The terrain tiles use the Web Mercator grid of web maps. At zoom z the world is 256 × 2^z pixels wide, and a latitude and longitude become a pixel position with:

At zoom 15 one pixel is about 4.8 m at the equator, 3.4 m at 45° and 2.4 m at 60°. The tool loads every tile that touches the square, usually 4 to 16, and joins them into one grid.

2. Turning Colours Into Heights

The Terrarium format stores each height in the red, green and blue of a pixel, with a resolution of 1/256 m:

Heights below -500 m (lower than any dry land on Earth) or above 9,000 m are treated as missing. A few tiles have thin seams of wrong values along their edges: a pixel more than 120 m from the median of its eight neighbours is removed, and small gaps are filled with the average of their neighbours. Real cliffs survive this test, because half of their neighbours are on the same side. Wider seams and narrow trenches a few pixels across are caught by a second test: a pixel that lies below (or above) the pixels 2 to 6 places away on both sides, by more than a 200% slope over that distance, is removed too, with the pixels right next to it. A real cliff is a step, high on one side and low on the other, so it passes. Where a zoom-15 tile is empty, the tool uses the matching part of the tile one level up.

3. Smoothing

Light smoothing replaces each height by the average of the 3 × 3 pixels around it; strong smoothing uses two passes of a 5 × 5 average. Missing pixels are skipped. Pixels outside the square are then removed, so the lines stop at its edge.

4. Tracing the Lines: Marching Squares

For every square of four neighbouring pixels and every contour level h, the tool marks each corner as above or below h. That gives 16 possible cases, and each case says which edges of the square the line crosses. The exact crossing point on an edge between heights a and b is found by linear interpolation:

Two cases are saddles, where opposite corners are high. The tool looks at the average of the four corners to decide which way the line runs, so lines never cross. Each crossing point is named after its edge, so the pieces from neighbouring squares join exactly into long lines. Finally the Douglas-Peucker method removes points that lie within 0.35 pixel of a straight line, which keeps the files small without changing the shape.

5. Slope, Relief and the Height Chart

The slope at each pixel comes from the height differences to its left, right, upper and lower neighbours (central differences):

The relief is the highest height minus the lowest in the square. The mean elevation and the mean slope are averages over all pixels in the square. The steepest slope shown is the 99.5th percentile: only 0.5% of the area is steeper, so a single wrong pixel cannot set the figure. The height chart counts the pixels between each pair of contour levels (grouped when there are many) and divides by the total.

Elevation Data: AWS Terrain Tiles

The heights come from AWS Terrain Tiles, a free public dataset in the Registry of Open Data on AWS, first built by Mapzen. It merges many elevation models into one worldwide set of tiles: SRTM (NASA) for most land between 60° N and 56° S, USGS 3DEP (formerly the National Elevation Dataset) in the United States, EU-DEM in Europe, ArcticDEM in the far north, national models from several countries, and global models such as GMTED and ETOPO1 to fill gaps and the sea floor. The tool reads the Terrarium PNG version at zoom 15. The real detail depends on the source for each place, from about 10 m or better in much of the USA to about 30 m in many other places.

Maps and Search

The Terrain and Satellite maps are Esri World Topo Map and Esri World Imagery. The Street map is Maplity’s own vector basemap, built from OpenStreetMap data with Protomaps tiles hosted by KONAKTIVE, with CARTO and OpenStreetMap maps as fallbacks. The Terrain map opens first, at up to zoom 19, and if the Esri maps do not load, the tool switches to the Street map by itself. Place search uses Nominatim, the OpenStreetMap geocoder.

Software Libraries

The map, the contour lines and the labels are drawn with Leaflet 1.9, using its canvas renderer so that hundreds of lines stay fast. The PDF is built in your browser by jsPDF. The page runs on Next.js and React. The terrain decoding, the cleaning, the smoothing, the marching squares, the line joining and simplification, the drawing and the GeoJSON, KML and DXF writers are Maplity’s own code, with no contour library.

Limits of the Data

Terrain models measure the ground with a grid, so anything smaller than a few cells, such as a bank, a ditch, a wall or a single building, does not show. Where the dataset joins two sources, or fills a gap in one, the lines can show a straight edge or a blocky patch; the crater of Vesuvius has one. Some sources include buildings and trees (SRTM is a surface model), which can add bumps in towns and forests. Over the sea, lakes and wide rivers, the tiles hold water depths or the water surface, so the lowest point near a coast can be under water. For construction, boundaries and flood design, use a land survey or national lidar data.

How These Figures Were Made

The tables show the ground in a 1 km² square (1 × 1 km) around the same 200 famous places that are described on our Elevation Profile Viewer page. Each row was computed with this tool’s own engine: the default 1 km² square, light smoothing and the automatic interval. Relief is the difference between the highest and the lowest point in the square, Over 30% is the share of the area steeper than 30%, and Interval is the contour interval Auto would choose. Near coasts and lakes the lowest point can be under water, because the tiles include depths. In every row the relief is the highest minus the lowest height as printed, and the terrain type and the interval follow from that relief.

These heights can differ from the readings on the Elevation Profile Viewer page, because the two tools use different data. That page uses SRTM, which measures the top of buildings and trees. This tool uses AWS Terrain Tiles, which in the USA come from USGS 3DEP, a bare-ground model. So city landmarks read lower here: the Empire State Building site reads 43 m in SRTM but 8 to 24 m of ground in the 1 km² square here, and the Vehicle Assembly Building at Kennedy Space Center 83 m against -1 to 14 m.

Among the 200 places, 33 are mountainous in the 1 km² square, 41 have steep hills, 44 are hilly, 68 are gently rolling and 14 are flat. The largest relief is around Matterhorn summit (1,056 m) and the smallest around Shark Valley, Everglades National Park (3 m). The steepest ground on average is around Grand Teton summit, Half Dome summit, Yosemite and Matterhorn summit.

Terrain in a 1 km² Square Around 100 Famous Places in Europe

Terrain in a 1 km² Square Around 100 Famous Places in the USA

More Free Terrain Tools

• Contours to DEM Converter: the reverse of this tool, turn contour lines (GeoJSON, KML, Shapefile or DXF) into a DEM.
• Elevation Profile Viewer: an elevation chart along a route of up to 5 points.
• Map Elevation Finder: click one place and get its elevation.
• Slope and Gradient Calculator: the grade of a path in percent, degrees and a 1:x ratio.