Guide · updated 2026-09-30
How many decimal places do GPS coordinates need?
Short answer
Ground size of the last decimal
The table shows how far apart two coordinates are when they differ by one unit in the last decimal place, computed on the WGS84 ellipsoid. East-west size shrinks with latitude, so the 40° column is smaller for longitude.
| Decimals | Example | Latitude step | Longitude step at 0° | Longitude step at 40° |
|---|---|---|---|---|
| 0 | 40 | 111.0 km | 111.3 km | 85.4 km |
| 1 | 40.0 | 11.1 km | 11.1 km | 8.5 km |
| 2 | 40.00 | 1.1 km | 1.1 km | 854 m |
| 3 | 40.000 | 111 m | 111 m | 85 m |
| 4 | 40.0000 | 11 m | 11 m | 8.5 m |
| 5 | 40.00000 | 1.1 m | 1.1 m | 85.4 cm |
| 6 | 40.000000 | 11.1 cm | 11.1 cm | 8.5 cm |
| 7 | 40.0000000 | 1.1 cm | 1.1 cm | 0.85 cm |
| 8 | 40.00000000 | 0.11 cm | 0.11 cm | 0.09 cm |
What each precision can identify
- Two decimals, about 1.1 km: a town or a neighborhood.
- Three decimals, about 111 m: a village center or a large field.
- Four decimals, about 11 m: a building or a parcel.
- Five decimals, about 1.1 m: a doorway or a parking space, near the limit of a phone GPS in the open.
- Six decimals and beyond: survey work with correction services. Extra digits from a phone add no real information.
How precise are the coordinates on this site?
The county internal points on this site carry up to 4 decimals, as published in the Census Gazetteer, which is about 11 meters. That is far finer than the question it answers, since an internal point stands for a whole county. The Census Bureau places it at the centroid when the centroid falls inside the county, and otherwise at a nearby point inside the boundary, preferably on land.
False precision
A coordinate with eight decimals looks exact, but the digits are only as good as the measurement. A geocoded address may be placed by interpolating along a street, which can put it tens of meters from the front door. A city's coordinate is a chosen point, not a measurement. Round to the precision you actually have, and say what the point represents.
Storing more digits costs nothing in most databases, so keep what the source gives. When you display coordinates or compare them, round. Two readings of the same spot will almost never agree at the sixth decimal.
Decimals and seconds of arc
One second of latitude is about 30.8 meters at 40°. Four decimals are about a third of a second, and five decimals about a thirtieth. So a DMS coordinate given to whole seconds sits between four and five decimals of precision. The DMS conversion guide covers the arithmetic.
Worked example: rounding a county point
The Census internal point of Cook County, Illinois is 41.8943, -87.6455. Rounding both values moves the point. The table shows how far, measured with the haversine formula:
| Decimals | Rounded coordinate | Moved by |
|---|---|---|
| 1 | 41.9, -87.6 | 3.8 km |
| 2 | 41.89, -87.65 | 606 m |
| 3 | 41.894, -87.645 | 53 m |
Rounding can move a point by up to half a unit in each direction, so the worst case is about 0.7 of the step in the table above. The actual shift depends on how close the original digits were to a rounding boundary.
Choosing a precision for a dataset
Match the decimals to what the point represents. A county or city label point needs no more than three or four decimals. A building entrance or a survey marker needs five or six. For aggregate data such as counts by ZIP code or county, the point is a label, and extra decimals imply a precision the data does not have.
When publishing, say how the point was made: GPS reading, geocoded address, centroid or internal point. That tells readers more about accuracy than the number of decimals.
Try it
GPS coordinate converter
Convert decimal degrees, DMS, DMM, UTM, geohash, and plus codes, with what each decimal place means on the ground.
Decimal to DMS, worked with your input
Latitude 39.739000 degrees = floor(39.739000) = 39 minutes = floor(0.739000 × 60) = 44 seconds = 0.340000 × 60 = 20.40 result = 39° 44' 20.40" N Longitude -104.985000 degrees = floor(104.985000) = 104 minutes = floor(0.985000 × 60) = 59 seconds = 0.100000 × 60 = 6.00 result = 104° 59' 6.00" W
Same point, six formats
- Decimal degrees
- 39.739000, -104.985000
- DMS
- 39°44'20.40"N 104°59'6.00"W
- DMM
- 39°44.3400'N 104°59.1000'W
- UTM
- 13N 501285.3E 4398789.5N
- Geohash
- 9xj654222
- Plus code
- 85FQP2Q7+JX
- Your precision
- 3 decimalsabout 111 m north-south, 85.7 m east-west
Questions people ask
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.
How accurate is 4 decimal places of latitude?
About 11 meters, enough to identify a building.
How many decimals should I store?
Store what the source provides. Display five or six decimals for GPS readings and fewer for geocoded places.
Why is longitude precision different?
A degree of longitude shrinks with the cosine of latitude, so each decimal of longitude covers less ground away from the equator.
Sources and data as of
Data as of: computed from the WGS84 defining constants.
- 01Census Bureau geography glossary (last verified 2026-09-30)
How every number is computed: methodology. Spotted a wrong figure? Report an error.