Length of a Degree Calculator

Counterintuitive but exact: Earth's flattening makes the polar regions less curved (a flatter arc), and a degree of arc on gentler curvature spans more distance — 111.69 km at the pole versus 110.57 at the equator. Don't confuse the radius (smaller at poles) with the curvature radius along the meridian (bigger at poles); degree length follows the latter. The 1% variation mattered enough that 18th-century expeditions to Lapland and Peru measured it to settle whether Earth was lemon- or orange-shaped. Newton's orange won.

It's the metre's own origin story inverted: the metre was defined (1795) as one ten-millionth of the pole-to-equator quadrant, making that quadrant 10,000 km and each of its 90 degrees ≈ 111.11 km by construction. The modern WGS-84 value averages 111.13. The companion constants worth memorizing: 1 minute of latitude = 1 nautical mile = 1,852 m (exactly, by definition), and 1 second ≈ 30.9 m — the mental rulers of every chart user.

The flat-Earth approximation that's legitimately fine for short distances: Δnorth ≈ Δlat° × 111.1 km; Δeast ≈ Δlon° × 111.3 × cosφ km; distance = √(Δn² + Δe²). Under 100 km it agrees with the haversine to ~0.1%; by 1000 km errors reach a percent or two — switch to the proper great-circle tool. This is also exactly the math inside our geofence calculator's bounding boxes and most 'is it nearby' code in production apps.

Because the fourth decimal of latitude is always ~11.1 m, but the fourth decimal of longitude is 11.1 × cosφ — only 5.5 m at 60°N. Geo-developers learn this debugging map jitter: position noise that looks circular in metres looks ELLIPTICAL in raw degrees, stretched north-south on the screen at high latitudes (the reverse once you project). Any pixel-per-degree mapping, screenshot georeferencing, or quick CSV-to-map work needs this page's two numbers — one per axis, never one for both.