Map & Navigation Toolkit
UTM and latitude/longitude conversion both ways, map scale distances, bearings with declination, and pace-count calibration.
Latitude / longitude → UTM
UTM → latitude / longitude
Reading a UTM grid reference
A UTM reference is a zone number, a latitude band letter, and two distances in metres: easting first, then northing. Easting is measured from a false origin 500,000 metres west of the zone's central meridian, so a point exactly on the central meridian always reads 500,000 — which is a useful sanity check when you think you have mistyped something.
Northing is metres from the equator going north. In the southern hemisphere the equator is given the value 10,000,000 and numbers count down from it, so southern northings are large. This is why a hemisphere is part of the reference and not an optional extra: the same numbers describe two different places without it.
Common scales
| Scale | Inches per mile | cm per km | Notes |
|---|---|---|---|
| 1:24,000 | 2.64 | 4.2 | The US Geological Survey 7.5-minute quad — the standard American topo. One inch is 2,000 feet. |
| 1:25,000 | 2.53 | 4.0 | The common metric equivalent, used across Britain (Explorer series) and much of Europe. Four centimetres to the kilometre. |
| 1:50,000 | 1.27 | 2.0 | The military and Landranger standard. Covers ground fast, less detail underfoot. |
| 1:62,500 | 1.01 | 1.6 | The old US 15-minute quad. Almost exactly one inch to the mile, which is why it survived so long. |
| 1:100,000 | 0.63 | 1.0 | Regional planning scale. Useful for driving to the trailhead, not for finding it. |
| 1:250,000 | 0.25 | 0.4 | State and regional overview. One inch is about four miles. |
Bearing between two points
Magnetic ↔ true
East declination is positive, west is negative. Going from a compass bearing to a map bearing you add east declination; going the other way you subtract it. Getting the sign backwards is the classic navigation mistake, and it is a nasty one because it does not cancel — it doubles your error. At 13 degrees, being wrong in the wrong direction puts you 26 degrees off, which is roughly half a kilometre adrift after two kilometres of walking.
Declination is not a constant. It varies by location and drifts measurably year on year, so the value printed on an old map may be several degrees stale. Check a current figure for your area rather than trusting the margin of a map from the nineties.
Calibrate
Paces for a leg
How pace counting actually works
A pace is two steps — you count once every time the same foot lands. Calibrate on a measured 100 metres of flat ground, walking the way you normally walk rather than carefully. Most adults land somewhere between 60 and 70. Anyone quoting a number they have not measured themselves is guessing, and the whole technique depends on the number being yours.
Terrain stretches the count, sometimes badly — steep uphill can add a third. The practical trick is to move a pebble between pockets, or a bead on a ranger cord, every 100 metres. Counting to 260 while navigating and watching your footing is how people lose track and end up trusting a number they invented.
How to use
- Coordinates: convert latitude and longitude to a UTM grid reference, or a grid reference back to a position.
- Map scale: measure a distance on paper and get the real ground distance in metres, kilometres and miles.
- Bearings: get the bearing and distance between two points, and convert between compass and map north.
- Pace count: calibrate over a measured 100 metres, then get the count for any leg on any terrain.
Frequently asked questions
Why does easting always read 500,000 on the central meridian?
Because easting is measured from a false origin placed 500,000 metres west of each zone's central meridian, so no point in the zone ever has a negative easting. It doubles as a sanity check — if you are on the central meridian and see anything else, something is mistyped.
Why are southern hemisphere northings so large?
The equator is given the value 10,000,000 in the south and numbers count down from there, again to avoid negatives. It is also why the hemisphere is part of a grid reference and not an optional extra — without it, the same pair of numbers describes two different places.
Do I add or subtract magnetic declination?
East declination is positive. Compass to map, you add it; map to compass, you subtract. Getting the sign backwards is the classic navigation error and a nasty one, because it does not cancel — it doubles your error. At 13 degrees, being wrong the wrong way puts you 26 degrees off.
How do I calibrate a pace count?
Walk a measured 100 metres on flat ground, counting every time the same foot lands — a pace is two steps. Most adults land between 60 and 70. The technique only works if the number is genuinely yours, so a figure you read somewhere is worse than useless.
How accurate is the UTM conversion?
It uses the standard Snyder series on the WGS84 ellipsoid and round-trips to within a few millimetres worldwide. The widened Norway and Svalbard zones are less accurate, since a point can sit six degrees from the central meridian rather than three, but the error there is still centimetres.
🔒 This tool runs entirely in your browser. Nothing you enter is uploaded, logged, or stored.