By the Map With Radius editorial team · Last reviewed 29 May 2026
A kilometer radius tool for technical and regulatory work
Most online radius tools target US miles users and only mention kilometers as an afterthought. This page is the opposite: it's the radius tool oriented around the regulatory, planning, and GIS conventions of the metric world, where radii get used for things like air-quality zones, school catchments, bushfire perimeters, EU short-haul flight thresholds, and Japanese station-walking distances. The interactive tool above defaults to kilometers; the rest of this page is the reference material that goes with it.
If you're looking for the general radius tool with imperial defaults and broader consumer examples, the miles-default home page covers that. For travel-time isochrones (rather than straight-line radii), see the drive-time map or walking radius map.
How regulatory radii are defined in metric systems
Metric-using jurisdictions tend to anchor regulatory radii on round numbers — 5, 10, 25, 50, 100 km — where US/UK regulations cluster on 1, 5, 10, 25, 50 miles. That difference matters in practice: a US planner reading a European emergency-response policy that mandates “10 km coverage” should not mentally convert it to 6.2 mi and stop there. The 10 km figure is chosen because it's the operational round number the regulation was written around, not because it's a precise maximum.
There's also a definitional gap worth flagging. “Within 10 km” in a regulation can mean any of three things:
- Straight-line (Euclidean) distance — the great-circle distance a radius tool draws. Common for environmental, atmospheric, and emergency-broadcast rules.
- Road network distance — distance along drivable roads. Common for tax, commuter-relief, and delivery regulations.
- Travel time (sometimes phrased as “within 15 minutes”) — common for response-time SLAs and 15-minute-city analyses, computed as an isochrone rather than a circle.
The tool above draws Euclidean radii. For network-distance use cases, the distance calculator also returns road-distance via OSRM; for travel-time, see the isochrone tools linked above. Pick the right measurement type before you start sketching a regulatory polygon on the map.
Field guide: four worked examples
Concrete cases where a kilometer radius is the right tool — drawn from public regulation and planning documents. Each example notes the radius value, what defines it, and which gotchas to watch for when you sketch it on the tool above.
1. German Umweltzone: planning a Low Emission Zone
Germany's air-quality framework, implementing the EU Ambient Air Quality Directive (2008/50/EC), lets cities declare Umweltzonen — Low Emission Zones where older vehicles can't drive. The original Berlin Umweltzone, for example, sits inside the S-Bahn Ringbahn, roughly a 4 km radius from Alexanderplatz. When a smaller city designs a new zone, planners typically start by drawing a 3–5 km radius around the historic center, then refine to a polygon that follows actual ring roads.
Radius used: 3–5 km Euclidean from center, refined to polygon. Gotcha: the regulation is enforced on a polygon, but the radius is the planning shortcut. Don't conflate them.
2. Carlos Moreno's 15-minute city as a 1.2 km screen
The 15-minute city framework — adopted by Paris, Melbourne, Portland, and others — measures whether daily essentials are reachable within a 15-minute walk. The rigorous version uses pedestrian isochrones; the screening version uses a straight-line radius of roughly 1.2 km (15 min × 5 km/h walking speed). For city-wide audits, planners start with the radius approximation to identify candidate “15-minute neighborhoods,” then drill in with isochrone analysis on the candidates that pass screening.
Radius used: 1.2 km Euclidean (screening) → walking isochrone (refinement). Gotcha: the radius will over-count in cities with rivers, freeways, or steep grade — fine for screening, wrong for delivery of services.
3. Japanese station-walking radius for property listings
Japanese real-estate listings universally quote “駅徒歩X分” (X-minute walk to station) at a regulated 80 m/min pace — so 5 minutes is 400 m, 10 minutes is 800 m. The 500 m station-walking radius is the de-facto property-listing catchment in Tokyo, Osaka, and most major cities. If you're calibrating a real-estate analysis for the Japanese market, the 500 m / 800 m radii are the only ones that actually drive consumer decisions.
Radius used: 500–800 m around each station. Gotcha: 80 m/min is the regulated pace, not a realistic average — actual walking speed in Tokyo is closer to 75 m/min on flat ground, slower in hilly Yokohama or Kobe. The listing radius overstates accessibility.
4. EU short-haul flight threshold debate
France banned short-haul domestic flights where a train alternative under 2.5 hours exists (2022 law); the broader EU debate proposes a 500–1,500 km threshold for similar restrictions. These distances are measured as great-circle (straight-line) between airport pairs — which is precisely the Haversine formula the tool above uses. The straight-line distance always understates the actual flight track, so a regulation written at 500 km great-circle effectively covers flights with ~550 km flight paths.
Radius used: 500–1,500 km great-circle between airport pairs. Gotcha: the regulatory distance is great-circle; the operational flight distance is longer. If you're modelling which routes fall inside a proposed threshold, use the straight-line measurement, not the airline's published kilometers.
Common kilometer-radius mistakes
Six failure modes we see repeatedly when teams sketch metric radii for the first time:
- Confusing km with km². A 10 km radius covers 314 km² (π·r²), not 10 km². When a regulation says “within a 10 km area,” check whether it means a 10 km radius (the common reading) or a 10 km² area (a much smaller circle of radius ≈ 1.78 km).
- Confusing radius with diameter. “A 10 km zone” in informal speech often means a 10 km diameter (5 km radius), especially in evacuation or quarantine contexts. Always check whether the source value is center-to-edge or edge-to-edge.
- Straight-line vs road distance. A 10 km radius in Manhattan covers walkable Manhattan; a 10 km road distance from Times Square may end up in New Jersey because of the Hudson crossings. For regulations that measure accessibility, road distance and Euclidean radius can disagree by 2× or more in coastal cities.
- Latitude distortion on Web Mercator. The map tiles use the Web Mercator projection, which stretches features near the poles. A 50 km circle in Stockholm looks much larger on screen than a 50 km circle in Nairobi, even though they cover the same ground. The radius value is correct; the visual size is not a reliable comparison.
- Earth oblateness for long ranges. Haversine assumes a perfectly spherical Earth. For radii under ~200 km the error is below 0.1%; at 1,000 km it can reach 0.3%. For aviation, maritime, or geodetic work, switch to a true ellipsoidal formula (Vincenty's).
- Edge-case rounding. If a regulation says “within 5 km,” is 5.0001 km inside or outside? Most regulations are inclusive at the boundary but it's worth confirming with the source document before deciding a marginal case.
GIS standards: WGS 84, EPSG codes, and INSPIRE
Three standards govern how kilometer-radius work moves between consumer tools and professional GIS pipelines:
- WGS 84 (EPSG:4326) — the geodetic datum used by GPS, OpenStreetMap, Google Maps, and all major consumer mapping. Latitudes and longitudes you copy out of any consumer tool, including this one, are in WGS 84 unless explicitly stated otherwise. Almost all global radius work uses this.
- ETRS89 (EPSG:4258) — the European Terrestrial Reference System, used by EU national mapping agencies and INSPIRE-compliant data. For consumer purposes ETRS89 and WGS 84 are interchangeable; the divergence is millimetric per year. Surveying-grade work needs to track which datum each layer is in.
- INSPIRE Directive (2007/2/EC) — requires EU member state agencies to publish spatial data in interoperable formats. KML and GeoJSON exports from this tool are INSPIRE-compatible when paired with the right metadata; the coordinates themselves are already in the right datum.
- Country-specific national grids — UK Ordnance Survey (OSGB36 / EPSG:27700), French Lambert-93 (EPSG:2154), German Gauß-Krüger (EPSG:31466–31469), Japan Plane Rectangular (EPSG:6669–6687). These are projected coordinate systems used for national cartography. Convert between them and WGS 84 in QGIS or proj4 before doing radius calculations on data that arrived in a national grid.
In practice: the radii you draw here can be exported as KML and dropped directly into QGIS, ArcGIS, Google Earth, or any tool that reads WGS 84. If your data arrives in a national grid, transform it to WGS 84 first; the radius math doesn't care about the projection but the visual overlay does.
How Far Is That? Walking Time Reference
To put kilometer distances in perspective, here's how long it takes to walk each distance at an average pace of 5 km/h (a comfortable walking speed):
| Distance | Walking Time | Cycling Time (15 km/h) | Driving Time (City) |
|---|
| 500 m | 6 minutes | 2 minutes | 2 minutes |
| 1 km | 12 minutes | 4 minutes | 3 minutes |
| 2 km | 24 minutes | 8 minutes | 5 minutes |
| 5 km | 60 minutes | 20 minutes | 12 minutes |
| 10 km | 2 hours | 40 minutes | 20-30 minutes |
Note: Actual travel times vary based on terrain, traffic, and route. For accurate travel time analysis, use our drive time map or walking radius map.
Converting KM to Miles
If you need to communicate distances with US or UK colleagues, multiply kilometers by 0.62 to get miles, or divide by 1.6.
Methodology and sources
The radius values cited on this page come from public regulation and statistics sources. Where a figure is jurisdictional (an Umweltzone size, a commute average), the underlying source is named below so you can verify against the primary document rather than relying on this page's summary.
- EU Ambient Air Quality Directive 2008/50/EC — underlying framework for German Umweltzonen and similar national Low Emission Zones.
- French Climate and Resilience Law (loi 2021-1104) — short-haul flight ban for routes with train alternatives under 2.5 hours.
- Japanese Real Estate Fair Trade Council guidelines — the 80 m/min walking-pace regulation used in 駅徒歩 listings.
- Carlos Moreno, “The 15-Minute City” (2016) — original framework for the walking-isochrone planning standard.
- IOGP / EPSG Geodetic Parameter Registry — authoritative source for coordinate reference system codes used in the GIS standards section.
All radius calculations on this site use the Haversine formula on a spherical Earth approximation. For exact ellipsoidal calculations (Vincenty's formulae), a dedicated GIS pipeline like QGIS or proj is required.