A geographic position can be written in several formats that look nothing alike but describe the same point on the ground. A phone reports 51.503333, −0.119722. A nautical chart writes 51°30′12.0″N 000°07′11.0″W. A survey drawing or a military map uses a UTM reference like 30U 699320 5710170. This coordinates converter takes any of the three and produces all three, using the WGS 84 ellipsoid throughout, and refuses to convert values that fall outside the legal range rather than returning a plausible-looking wrong answer.
Arb Digital builds free tools that fail loudly instead of quietly. That matters here more than in most conversions, because a coordinate error rarely announces itself — swap latitude and longitude in London and you land in the Indian Ocean, but swap them in a place where both values are similar and the result looks entirely reasonable. Nothing else on this site handles geographic coordinates: the UTM builder is about Urchin Tracking Module campaign parameters for web analytics, a completely unrelated meaning of the same three letters.
What This Coordinates Converter Does
Pick the format you are starting from, paste the coordinate, and read all three outputs. Decimal degrees appear in the hero panel at a precision you control. The grid shows latitude and longitude separately in degrees, minutes and seconds, then the UTM zone with its latitude band letter, and finally the easting and northing in metres.
The parser is deliberately tolerant about how you type things. Decimal degrees can be separated by a comma or by whitespace. Degrees-minutes-seconds accepts the degree, minute and second symbols, plain apostrophes and quotation marks, colons, or simply spaces, with the hemisphere letter before or after the numbers. UTM accepts the zone number followed by either a latitude band letter or a plain N or S, then easting and northing. What it will not do is guess: an unparseable input produces a message naming the problem.
Range checking is strict. Latitude must lie between −90 and +90 and longitude between −180 and +180. Minutes and seconds must be below 60. UTM zones must be between 1 and 60, and UTM itself is only defined between 80°S and 84°N, so a request outside that band is refused rather than extrapolated. Each of these produces a specific message rather than a generic failure.
How to Use It
- Select the format you are pasting in. The converter does not try to detect the format automatically, because several formats are genuinely ambiguous and a wrong guess is worse than an extra click.
- Enter latitude before longitude. This is the universal convention in geography, and reversing it is the single most common mistake in coordinate handling.
- Use the hemisphere letter or a minus sign, not both. Writing −51°S is contradictory. South and west are negative in decimal degrees; in DMS they are indicated by the letter.
- Choose a sensible precision. Six decimal places is about eleven centimetres of latitude, which is finer than any consumer GPS receiver can justify.
- Check the UTM band letter. It encodes the latitude band and is not simply north or south, which is a frequent source of confusion when copying references between systems.
The Formula: How These Conversions Work
Decimal degrees to degrees-minutes-seconds is straightforward arithmetic. Take the absolute value, the whole part is the degrees, multiply the remainder by 60 for minutes, take the whole part, multiply that remainder by 60 again for seconds. Going the other way, decimal degrees = degrees + minutes ÷ 60 + seconds ÷ 3,600, with the sign applied from the hemisphere. As NOAA's National Ocean Service explains in its overview of what latitude is, one degree of latitude is roughly 111 kilometres, and it is subdivided into 60 minutes and 3,600 seconds for precision.
UTM is an entirely different kind of transformation. It is a projection, not a re-expression: the curved surface of the ellipsoid is mapped onto a flat grid in metres. The world is divided into sixty zones each six degrees of longitude wide, and within each zone a transverse Mercator projection is applied with a central scale factor of 0.9996. Eastings are offset by a false easting of 500,000 metres so no value is negative, and southern-hemisphere northings carry a false northing of 10,000,000 metres for the same reason.
The forward projection uses the standard series expansion in terms of the meridional arc length M, the radius of curvature in the prime vertical N, and powers of A = cos φ × (λ − λ₀). The ellipsoid parameters are those of WGS 84: semi-major axis a = 6,378,137 metres exactly, and flattening f = 1 ÷ 298.257 223 563. The inverse projection reverses the series through a footpoint latitude. NOAA's National Geodetic Survey publishes the authoritative implementation of these transformations in its NGS Coordinate Conversion and Transformation Tool, which also handles datum transformations that this page does not attempt.
The metre itself, in which every UTM value is expressed, is one of the seven SI base units described in NIST's guidance on SI units. That is worth noting because it is the reason UTM is convenient for engineering: distances between two points in the same zone can be computed with ordinary plane geometry, in metres, without any spherical trigonometry.
Why UTM Exists and When to Use It
Latitude and longitude are angles, and angles are awkward for measurement. A degree of latitude is roughly constant at about 111 kilometres, but a degree of longitude shrinks from 111 kilometres at the equator to nothing at the poles. Calculating the distance between two points from their angular coordinates requires spherical trigonometry, and calculating an area requires worse.
UTM converts a local region into flat metres, so distance is Pythagoras and area is length times width. Survey work, construction setting-out, military mapping and most GIS analysis therefore prefer it. The cost of that convenience is distortion: a transverse Mercator projection is only accurate near its central meridian, which is why the world is chopped into sixty separate zones rather than projected as one.
The scale factor of 0.9996 at the central meridian is a deliberate compromise. It makes the projection slightly too small in the middle of the zone and slightly too large at the edges, so the maximum scale error anywhere in the zone is about one part in 2,500 rather than being concentrated at one edge. Over a kilometre that is 40 centimetres — negligible for navigation and significant for precise survey, which is exactly why surveyors apply scale corrections.
Zone Boundaries and the Exceptions That Break Them
The regular rule is that zone number = floor((longitude + 180) ÷ 6) + 1, giving zone 1 from 180°W to 174°W and zone 60 from 174°E to 180°E. Two regions break that rule for historical reasons, and any converter that ignores them produces references that do not match published maps.
Zone 32 is widened westward between 56°N and 64°N so that southwest Norway falls in a single zone. And around Svalbard, above 72°N, zones 31, 33, 35 and 37 are widened while 32, 34 and 36 are eliminated entirely. This converter implements both exceptions, so a coordinate in western Norway returns zone 32 rather than the 31 that naive arithmetic would give.
Working across a zone boundary is its own hazard. Two points a few hundred metres apart on either side of a boundary have completely different eastings, and subtracting them gives a meaningless number. If a project spans a boundary, either extend one zone's coordinates across it — which surveyors do, accepting the extra distortion — or use a geographic coordinate system instead.
Why the Datum Matters as Much as the Format
A coordinate without a datum is incomplete, in the same way a length without a unit is incomplete. The datum defines the shape and position of the reference ellipsoid the coordinate is measured against. This converter uses WGS 84 throughout, which is what GPS receivers report and what web mapping services use.
The size of the disagreement between datums is not trivial. The same physical point expressed in the older North American Datum of 1927 and in WGS 84 can differ by more than a hundred metres. Local datums such as OSGB36 in Britain differ by tens to hundreds of metres from WGS 84 depending on where you are. Converting between formats within one datum, which is what this page does, is exact arithmetic. Converting between datums is a different operation entirely, requiring a transformation model, and the NGS tool linked above is the right place for it.
The practical rule is simple: if a coordinate came from a GPS device, a phone or a web map, it is almost certainly WGS 84 and this converter applies. If it came from an old paper map, a legacy survey or a national grid system, check the datum printed on it before assuming anything.
Reading Precision Honestly
Decimal places imply accuracy, and it is easy to imply more than you have. At the equator one degree of latitude is about 111,320 metres, so four decimal places is about 11 metres, five is about 1.1 metres, six is about 11 centimetres and seven is about 1 centimetre. For longitude those figures shrink by the cosine of the latitude, so at 60° north a degree of longitude covers only half the ground it does at the equator.
A consumer GPS fix is typically accurate to somewhere between three and ten metres in the open, and considerably worse among tall buildings or under tree cover. Quoting such a position to seven decimal places is arithmetic theatre. Four to six decimal places, or DMS to one decimal second, matches what most devices can actually justify.
If you need the distance between two coordinates rather than a reformatting of one, use the great circle distance calculator, which computes along-surface distance properly rather than treating the Earth as flat. For angle unit work, the angle converter handles degrees, radians and gradians; for the metric side of UTM values, the length converter and the unit converter. Positions and local time are related through longitude, which is where the timezone converter becomes useful, and the moon phase calculator is another location-aware tool worth knowing about. Everything else is on the free tools hub.
Arb Digital builds free tools like this one because useful pages earn attention. If you want tools, calculators or content built for your own audience, we can help.
Browse All Free Tools Talk to Arb DigitalCommon Mistakes to Avoid
- Writing longitude first — geographic convention is latitude then longitude. Some data formats reverse it, which is exactly why the error is so persistent.
- Combining a minus sign with a hemisphere letter — −51°S says the same thing twice and contradicts itself. Use one or the other.
- Assuming every coordinate is WGS 84 — older maps and national grids use different datums, and the same point can differ by more than a hundred metres between them.
- Subtracting UTM eastings across a zone boundary — the two values are measured from different central meridians, so the difference is meaningless.
- Quoting more decimal places than the source supports — seven places is a centimetre, which no consumer receiver delivers.
Related Free Tools From Arb Digital
For distances between two positions use the great circle distance calculator. For angle units, the angle converter; for the metres in a UTM reference, the length converter or the unit converter. Location-linked time questions belong in the timezone converter, and the moon phase calculator is another position-aware tool. If you arrived here looking for campaign tracking parameters instead, that is the UTM builder. Everything else is on the free online tools hub.
Frequently Asked Questions
WGS 84 throughout, with a semi-major axis of 6,378,137 metres and a flattening of one over 298.257223563. That is the datum used by GPS receivers and web mapping services. It converts between formats within that datum and does not transform between different datums.
Take the whole number part as degrees, multiply the fractional remainder by 60 and take the whole part as minutes, then multiply that remainder by 60 for seconds. The sign becomes N or S for latitude and E or W for longitude.
The zone is one of sixty six-degree strips of longitude, numbered eastward from the 180th meridian. The band is a letter marking an eight-degree strip of latitude. Together they identify which projected grid the easting and northing belong to.
Because the transverse Mercator projection distorts severely at extreme latitudes. UTM is defined only between 80 degrees south and 84 degrees north, and the polar regions use the Universal Polar Stereographic system instead.
Yes. Zone 32 is widened westward between 56 and 64 degrees north for southwest Norway, and above 72 degrees north the Svalbard zones 31, 33, 35 and 37 are widened while 32, 34 and 36 do not exist. Both rules are implemented.
It is rejected with a message naming the problem. Latitude beyond 90 degrees, longitude beyond 180, minutes or seconds of 60 or more, and UTM zones outside 1 to 60 all produce a specific error rather than a plausible but incorrect result.
Four is about 11 metres of latitude, five about 1.1 metres and six about 11 centimetres. A consumer GPS fix is good to a few metres at best, so quoting seven decimal places implies an accuracy the source does not have.
This tool is provided for general reference and educational use. It performs coordinate format conversion within a single datum and is not intended for navigation, surveying, legal boundary determination or any safety-critical purpose.
