Compass & Azimuth

Live compass and the azimuth calculators — declination, conversions, back azimuth, and mils.

Live Compass

magnetic

Uses your device's magnetometer. Hold the phone flat and away from metal, vehicles, and electronics — they deflect the reading.

Declination Diagram (LARS)

TC 3-25.26

Read the two values off your map's declination diagram and enter them. The solver finds the G-M angle and applies LARS — Left Add, Right Subtract — to convert a grid azimuth to a compass heading.

GN value (° from TN)GN side of TN

MN value (° from TN)MN side of TN

›GN is 1.5° left (west) of TN; MN is 10.9° right (east) of TN.

›GN and MN are on OPPOSITE sides of TN → ADD: 1.5° + 10.9° = 12.4° G-M angle.

›MN is on the RIGHT of GN → LARS says SUBTRACT when going grid → magnetic.

G-M angle12.4°(≈220 mils)

Grid azimuth (°)

Set on compass (magnetic)

347.6°

Cross-check before you march

Grid

0.0°

Magnetic

347.6°

Back-az (mag)

167.6°

MN right of GN → grid − G-M. Confirm the add/subtract matches your map's declination diagram.

Quick Converters

G-M angle from map margin (° — east +, west −)

Default 12.4°E for St. George, Utah (2026). Use the G-M angle printed on yourmap (grid↔magnetic), not a true-north declination — it's location-specific and drifts over time. Enter west as a negative number.

Grid azimuth →Magnetic azimuth →

Type in either box; the other updates. East declination subtracts going grid→magnetic.

Back azimuth

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Degrees → mils

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Mils → degrees

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