How far is one degree on the ground? The answer depends on which way you go. You will use degrees and minutes and multiplication.
Key idea
One degree of latitude is about 111 km (69 miles) everywhere. One degree of longitude is about 111 km at the equator but shrinks toward the poles: about 85 km at 40°, 56 km at 60°, and 0 at the poles.
Why it works
Earth is about 40,000 km around. A full circle is 360°, so one degree of latitude is about 40,000 ÷ 360 ≈ 111 km. Parallels are all the same distance apart, so this works everywhere. But meridians meet at the poles. The circle of a parallel gets smaller as you go north, and the same 1° of longitude covers a shorter and shorter piece of it. (The size of that circle is the equator's size times the cosine of the latitude: half as big at 60°.)
| Latitude | 1° of longitude is about |
|---|---|
| 0° (equator) | 111 km |
| 20° | 104 km |
| 40° | 85 km |
| 60° | 56 km |
| 80° | 19 km |
| 90° (pole) | 0 km |
Worked example: North to south
Two towns are on the same meridian, at 32° N and 37° N. About how far apart are they?
- They differ by 37 − 32 = 5 degrees of latitude.
- Each degree of latitude is about 111 km.
- 5 × 111 = 555 km.
Answer: About 555 km.
Worked example: East to west
Two towns are both at 60° N, 4° of longitude apart. About how far apart are they?
- At 60°, one degree of longitude is about 56 km (half of 111).
- 4 × 56 = 224 km.
- At the equator the same 4° would be 444 km.
Answer: About 224 km.
Worked example: One minute
About how far is one minute of latitude?
- A degree of latitude is about 111 km and has 60 minutes.
- 111 ÷ 60 ≈ 1.85 km.
- That is one nautical mile, the unit sailors and pilots use.
Answer: About 1.85 km.
Common mistake
Using 111 km for every degree of longitude. That is true only at the equator. Before you multiply, ask which way you are going. North-south: 111 km per degree. East-west: smaller, unless you are near the equator. (The U.S. Geological Survey gives about 54.6 miles, or 88 km, for a degree of longitude at 38° N.)