GPS Coordinates for Hikers: Topo Maps, Garmin, and AllTrails

You've marked a waypoint on AllTrails, printed a USGS topo map, and your Garmin is showing something that looks nothing like either of them. Welcome to the world of coordinate formats — and why understanding them makes you a far more capable backcountry navigator.

What Format Is on Your Topo Map?

USGS 7.5-minute topo maps have a UTM grid printed in blue on them, with tick marks around the margins showing latitude and longitude in DMS. If you're using the grid lines, you're working in UTM; if you're using the margin markings, you're in DMS.

What Format Does Your Garmin Use?

Most Garmin handhelds default to DDM (Degrees Decimal Minutes), but this can be changed in Settings → Position Format to UTM, DD, or DMS. Match your device format to your map format to avoid conversion errors in the field.

AllTrails and Mobile Apps

AllTrails stores and displays coordinates in Decimal Degrees. When you tap a waypoint, the DD coordinate is shown. Most mapping apps (Gaia GPS, CalTopo) also use DD as their primary format, with options to switch for display purposes.

The Critical Skill: Converting in the Field

When you need to convert between formats quickly — say, a coordinate from a trip report (DD) needs to go into your Garmin (DDM) — knowing the formula helps. To convert DD to DDM: keep the degrees as-is, multiply the decimal remainder by 60 to get decimal minutes. Our DD to DDM guide covers this step by step.

Before heading out, use our converter to pre-convert all your waypoints into the format your device uses. Five minutes of prep prevents hours of confusion on the trail.

For more detail on hiking-specific coordinate use, see our complete guide to GPS coordinates for hikers.