Distance Calculator

Distance Calculator – Quick Cheat Sheet

Input format: decimal degrees (lat −90…+90, lon −180…+180). West/South are negative.
Model: great-circle distance via the Haversine formula on mean Earth radius (6,371,008.8 m).
Units: km, miles (1 mi = 1,609.344 m), nautical miles (1 nm = 1,852 m).
Bearing: initial forward azimuth from A to B, degrees clockwise from North.
Accuracy: treats Earth as a sphere; for survey-grade work, use geodesics on an ellipsoid (e.g., Vincenty).
Tip: Double-check sign (±) on longitudes—mixing E/W is a common source of big errors.

Formulas (brief)

a = \sin^2(\Delta\varphi/2) + \cos\varphi_1\cos\varphi_2\sin^2(\Delta\lambda/2), d = 2R\arctan2(\sqrt{a},\sqrt{1-a})
\theta = \operatorname{atan2}(\sin\Delta\lambda\cos\varphi_2, \cos\varphi_1\sin\varphi_2 - \sin\varphi_1\cos\varphi_2\cos\Delta\lambda)