Coordinate Converter and Distance Calculator

What does this coordinate converter do?

A coordinate converter turns the latitude and longitude of a point from one notation into another, and a good one also measures the distance, bearing and midpoint between two points. The same place can look very different depending on where you meet it. Big Ben, for example, is 51.50073, -0.12463 in Google Maps, 51°30'02.63"N 0°07'28.67"W in a guidebook and 30U 699565 5709431 on a UTM grid.

This tool works in two modes:

• Convert: It reads whatever you paste: decimal degrees, degrees minutes seconds (DMS), degrees decimal minutes (DDM), UTM, a Google Maps link or a geo: URI. Then it shows every format, the precision and map links on one screen.
• Two points: It calculates the distance on a sphere (haversine) and on the WGS84 ellipsoid (Vincenty), plus the initial and final bearing and the midpoint.

Everything runs in your browser; neither your coordinates nor your location reach a server. If you need to switch between length units afterwards, our unit converter helps. The tool covers WGS84, the datum of GPS and web maps; national grids and land registry systems are out of scope.

Decimal degrees, DMS and DDM: what is the difference?

All three formats describe the same angle; they only differ in how they write minutes and seconds. One degree has 60 minutes, and one minute has 60 seconds. So 51.5 degrees and 51° 30' are the same value.

• Decimal degrees (DD): 51.50073, -0.12463. Maps, software and structured data expect this format; south and west take a minus sign.
• Degrees minutes seconds (DMS): 51°30'02.63"N 0°07'28.67"W. It is common in atlases, surveying and teaching.
• Degrees decimal minutes (DDM): N 51° 30.044 W 000° 07.478. Sailors, pilots and geocachers like it, because one minute of latitude is roughly one nautical mile, that is 1,852 metres.

International notation uses the letters N, S, E and W for the hemispheres. The converter also reads German (O for east) and Turkish letters, commas as decimal marks and labels such as lat and lng. Whatever you paste, the output uses dots and N, S, E, W, so you can drop it straight into Google Maps.

How do you convert DMS to decimal degrees by hand?

Divide the minutes by 60 and the seconds by 3,600, then add both to the degrees. For Big Ben's latitude of 51° 30' 2.63", that gives 51 + 30 ÷ 60 + 2.63 ÷ 3,600 = 51.500731. If the point lies south of the equator or west of Greenwich, put a minus sign in front.

The reverse works in three steps:

1. Take the whole number as degrees. For -0.12463 that is 0, and the letter is W because the value is negative.
2. Multiply the rest by 60: 0.12463 × 60 = 7.4778, so the minutes are 7.
3. Multiply the new rest by 60: 0.4778 × 60 = 28.67 seconds. The result is 0° 7' 28.67" W.

Rounding is where most hand conversions go wrong. If the seconds round up to 60.00, you have to carry one minute, and sometimes one degree. The converter handles that carry for you. For decimal minutes, stop after step two and keep three decimals, for example 7.478.

How do you calculate the distance between two coordinates?

The coordinate converter's Two points mode uses two methods. The first is the haversine formula: it treats the Earth as a sphere and measures the great circle arc between the points. We use a mean radius of 6,371.0088 km. The formula is simple; however, according to Movable Type, a spherical model is typically off by up to 0.3 percent.

The second is the method Thaddeus Vincenty published in 1975, which works on the WGS84 ellipsoid. Because the Earth bulges at the equator and flattens at the poles, the ellipsoid gives the better answer; Movable Type puts its accuracy at about 0.5 millimetres. There is one rare catch: for nearly antipodal points the method may not converge. The tool detects that case and shows the spherical result with a warning instead.

For example, Big Ben to the Eiffel Tower is 340.56 km on the sphere and 340.91 km on the ellipsoid, a difference of 355 metres. These are straight line distances over the surface. Roads are longer, so for travel costs use the fuel cost calculator.

Initial bearing and midpoint: why does the shortest path curve?

On a flat paper map you would draw a straight line with a ruler. On a sphere, however, the shortest route is a great circle arc, and its compass direction changes along the way. That is why the tool gives two bearings: the initial bearing is the angle you set off on, and the final bearing is the angle you arrive on.

From the Brandenburg Gate in Berlin to Big Ben, for example, the shortest route starts at 268.4 degrees, just south of due west. On arrival the heading has turned to 257.8 degrees. The longer the route, the bigger that change.

The midpoint follows the same logic. Our converter finds the point halfway along the great circle arc with the spherical formula. That point is not the average of the two coordinates, and on long routes the gap reaches tens of kilometres. For Big Ben and the Eiffel Tower the midpoint is 50.18577, 1.11840, over the English Channel near the French coast.

When do you need UTM instead of latitude and longitude?

UTM (Universal Transverse Mercator) splits the world into 60 zones, each 6 degrees wide, and gives a position in metres as an easting (E) and a northing (N). It makes map reading, field measurement and engineering plans easier, because the values are metres rather than degrees.

• The scale factor on each zone's central meridian is 0.9996, and eastings start from 500,000 metres.
• In the southern hemisphere, northings count down from 10,000,000 metres.
• UTM covers 80° south to 84° north; the polar regions use UPS instead.
• Letters name 8 degree latitude bands; Great Britain, for instance, lies in bands U and V.

London sits in zone 30U, Paris in 31U. The tool also applies the zone exceptions for Norway and Svalbard, and it works in both directions: paste a value such as 30U 699565 5709431 and you get latitude and longitude back. For the series we follow Karney's 2011 paper on the transverse Mercator projection, which keeps the error far below a millimetre.

How many decimal places do you really need?

Each decimal place in decimal degrees makes the position about ten times more precise. One degree of latitude is roughly 111 kilometres, so:

• 1 decimal place is about 11.1 km (a region),
• 2 places about 1.1 km (a town),
• 3 places about 111 m (a neighbourhood),
• 4 places about 11 m (a building),
• 5 places about 1.1 m (a door),
• 6 places about 11 cm (a survey mark).

Along longitude, the same decimal place covers less ground as you move away from the equator, because the meridians converge towards the poles. In London one degree of longitude is about 69 km.

The converter reads the number of decimals you typed and shows the matching precision. For DMS it looks at the decimals of the seconds, and for DDM at those of the minutes. Five places are enough for everyday use. Seven or more places describe a centimetre or less, which no phone GPS can deliver, so the extra digits carry no real information.

Using a coordinate converter for local SEO and schema markup

Google asks that geo.latitude and geo.longitude in LocalBusiness structured data have at least 5 decimal places. That is why the coordinate converter prints a ready geo snippet under the results and checks the precision of your source.

Accurate coordinates help in three places:

• Your website: structured data on your location page describes the address and position to search engines in a consistent way. For the full markup, use our schema generator.
• Your Google Business Profile: the pin on the map and the coordinates on your site should point to the same spot.
• Direction links: a link with coordinates avoids mix-ups between streets with similar names. Put one on a flyer with the QR code generator.

We explain the steps to better local visibility in our Google Maps SEO guide, and the basics of structured data in our schema markup guide. If you want Talha Aslan and team to handle it end to end, see our SEO consulting service.