50 questions
Frequently asked questions
How to use this page
Key figures in one table
The numbers behind the most common questions, for the 50 states and DC.
| Figure | Value |
|---|---|
| County-equivalents | 3,144 |
| Residents, July 1, 2024 | 340,110,988 |
| Land, square miles | 3,533,469 |
| People per square mile | 96.3 |
| Median county population | 26,122 |
| Most populous county | Los Angeles County, CA |
| Largest county by land | Yukon-Koyukuk, AK |
| Highest county median income | Loudoun County, $173,655 |
| State with the most counties | Texas |
01 — 12 questions
Distance and direction
What formula calculates distance between two coordinates?
The haversine formula: d = 2R · asin(√(sin²(Δφ/2) + cos φ1 · cos φ2 · sin²(Δλ/2))), with latitudes φ and longitudes λ in radians and R the Earth's radius.
What radius should I use?
6,371.0088 km (3,958.76 miles) is the mean Earth radius used on this site. Rounding it to 6,371 km changes results by less than 2 parts per million.
How far off is averaging for short trips?
For Boston and Providence, 41 miles apart, the averaged point and the true midpoint are 203 feet apart.
Can I average latitude and longitude to find a midpoint?
Only for short distances. Between Sacramento and Boston the average misses the true midpoint by 201 miles.
How do I calculate bearing in Excel?
With latitudes in B2 and B3 and longitudes in C2 and C3: =MOD(DEGREES(ATAN2(COS(RADIANS(B2))*SIN(RADIANS(B3))-SIN(RADIANS(B2))*COS(RADIANS(B3))*COS(RADIANS(C3-C2)),SIN(RADIANS(C3-C2))*COS(RADIANS(B3))))+360,360).
Is bearing the same as azimuth?
In mapping, yes. Both are measured clockwise from north in degrees. Some fields measure azimuth from south, so check the convention.
Is a great circle always shorter than a rhumb line?
It is never longer. The two are equal along a meridian or the equator.
Why is a rhumb line straight on a Mercator map?
Mercator preserves angles, so a path that keeps one compass angle to every meridian plots as a straight line.
What is the quick formula in miles?
Distance in miles is about 1.22 times the square root of eye height in feet. At 6 feet that is about 3 miles.
How far can you see at sea level?
About 4.7 km (2.9 miles) with your eyes 1.7 m above the water, before refraction.
Which state capital has the nearest neighbor capital?
Washington and Annapolis, 30 miles apart, are each other's nearest capitals.
How far apart are Juneau and Honolulu?
2,811 miles in a straight line between the stored capitol coordinates.
02 — 12 questions
Coordinates and maps
How many miles is one minute of latitude?
About 1.15 miles, or 1,852 meters, at 45 degrees.
How many kilometers is one degree of latitude?
About 111.1 km, from 110.57 km at the equator to 111.69 km near the poles.
What is the range of latitude and longitude?
Latitude runs from -90 to 90 degrees and longitude from -180 to 180 degrees.
Which comes first, latitude or longitude?
Latitude, by convention. GeoJSON and some software store longitude first, so check the order before plotting.
How do I convert decimal degrees to degrees and minutes only?
Keep the whole degrees and multiply the fraction by 60. 36.1658 becomes 36 degrees and 0.1658 × 60 = 9.95 minutes.
How do I convert 40° 26' 46" N to decimal?
40 + 26/60 + 46/3600 = 40.4461.
How many decimals give one meter of precision?
Five decimals of latitude are about 1.1 meters, the closest level to one meter. Four decimals are ten times coarser.
How far does rounding to 3 decimals move a point?
At the Cook County internal point, rounding to 3 decimals moves the point 53 m. The worst case at 40 degrees is about 70 meters.
What UTM zones cover the contiguous US?
County internal points in the contiguous states fall in zones 10, 11, 12, 13, 14, 15, 16, 17, 18, 19.
From UTM zones explained
How do I find my UTM zone?
Zone = floor((longitude + 180) / 6) + 1, using decimal degrees with west negative. Denver at -104.985 is in zone 13.
From UTM zones explained
What is the area scale of Mercator at 45 degrees?
2.00 times, so land at 45 degrees is drawn twice as large as the same area at the equator.
Is Alaska bigger than Texas?
Yes. Alaska has 571,242 square miles of land and Texas 261,259, a ratio of 2.2. Mercator maps exaggerate the gap to about 8.1.
03 — 14 questions
Counties and codes
Is a FIPS code the same as a GEOID?
For states and counties, yes. GEOID is the Census name for the full identifier, which for a county is the 2 digit state code plus the 3 digit county code.
From FIPS codes explained
How many county FIPS codes start with zero?
318 of 3,144, all in states whose code is below 10.
From FIPS codes explained
Are Louisiana parishes counted as counties?
Yes. All 64 parishes are included in the total of 3,144.
How many counties does Texas have?
254, the most of any state.
Do independent cities belong to the surrounding county for statistics?
No. Census tables report them separately, and county totals exclude them. Add the rows yourself if you need a combined figure for a city and its surrounding county.
Is Carson City an independent city?
Yes. Carson City, Nevada is a county-equivalent with its own FIPS code, 32510.
Is there a county named after every president?
Not in this count. 10 of the 25 most common county names match a president's surname, and the list above shows how many states use each.
How many different county names are there?
1,804 distinct names across the 50 states, not counting independent cities, Connecticut planning regions and DC.
What share of US counties have more than 100,000 people?
19.8%, or 621 of 3,144 county-equivalents.
Is the median county population rising?
This site uses one vintage, so it cannot show a trend. Compare Vintage 2024 figures with a later vintage of the same Census release to see change.
What are Connecticut's planning regions based on?
The state's nine councils of governments, which the Census Bureau adopted as county-equivalents in 2022. Each region groups several towns, since Connecticut has no county governments.
What is the largest county-equivalent in the US?
Yukon-Koyukuk, Alaska, with 145,769 square miles of land.
Why is the internal point not the county seat?
The internal point is a geometric point near the center of the county's shape. The county seat is wherever the government sits, which can be anywhere in the county.
Does land area include ice and glaciers?
Yes. The Census glossary notes that glaciers, swamps and intermittent water are reported as land area.
04 — 8 questions
Population and income data
What is the least densely populated county?
Yukon-Koyukuk, AK, at 0.03 people per square mile.
How do I convert people per square mile to per square kilometer?
Divide by 2.589988, the number of square kilometers in a square mile. For example, 100 people per square mile is about 38.6 people per square kilometer.
Where is the population center of California?
The county method puts it at 35.56° N, 119.14° W, 246 miles from Sacramento.
What is a land center?
The same weighted average of county internal points, weighted by land area instead of population. It shows where the state's land is balanced, which is close to its geographic center.
Are population estimates the same as census counts?
No. The census is a count every ten years. Estimates are calculated for each year in between from births, deaths and migration.
When is a new vintage released?
The Census Bureau publishes a new vintage each year. Check its county population totals page for the current release before quoting a figure.
How many counties have a median household income above $100,000?
134 of 3,143 counties with a SAIPE 2023 estimate have a median household income of $100,000 or more.
Why does a county have no income estimate?
The SAIPE 2023 file this site uses has no value for it. The site shows the missing value as unavailable and leaves the county out of income rankings rather than filling the gap.
05 — 4 questions
Sunrise, sunset and daylight
What is civil twilight?
The period when the sun is between 0.833 and 6 degrees below the horizon, before sunrise and after sunset. The sky is usually bright enough for outdoor activity without lights.
Why is there more than 12 hours of daylight on the equinox?
Sunrise and sunset are counted when the sun's upper edge touches the horizon, and refraction lifts the sun's image. Both add a few minutes to each end of the day.
Why is there no sunrise on some days in the table?
Above the Arctic Circle the sun can stay up or stay down for a full day. The table shows 24 h or 0 h for those days.
Which US state capital has the longest June day?
Juneau, Alaska, with 18 h 17 min of daylight on June 21, 2026.
Sources and data as of
Data as of: Census Vintage 2024 population estimates, 2024 Gazetteer land area and internal points, SAIPE 2023 median household income.
- 01Census Vintage 2024 county population estimates
- 02Census 2024 Gazetteer, counties
- 03Census SAIPE 2023 state and county estimates
How every number is computed: methodology. Spotted a wrong figure? Report an error.