Straight Line Distance Calculator — Frequently Asked Questions
What is straight-line distance?
Straight-line distance (also called "as the crow flies," "air miles," or "geodesic distance") is the shortest distance between two points on Earth's surface. It follows the curvature of the Earth but ignores roads, terrain, and obstacles. It is calculated using the haversine formula from the latitude/longitude coordinates of each location.
What is the haversine formula?
The haversine formula is a mathematical equation that calculates the great-circle distance between two points on a sphere. Given the latitude and longitude of two locations, it determines the shortest path along Earth's surface. It accounts for Earth's curvature, making it more accurate than flat-surface calculations like the Pythagorean theorem — especially over longer distances.
Our tool uses an Earth radius of 3,958.8 miles (6,371.0 km) for calculations.
What types of locations can I enter?
You can enter any location that Google Maps recognizes:
- Full street addresses:
123 Main St, Springfield, IL 62701 - City and state:
Denver, CO - ZIP codes:
90210 - Landmarks:
Statue of Liberty - International addresses:
10 Downing Street, London, UK
For the best accuracy, use the most specific location format available. Full street addresses give coordinates within a few meters, while ZIP codes resolve to the geographic center of that area.
How accurate are the distance calculations?
Accuracy depends on two factors:
- Geocoding precision — How precisely Google Maps places each location. Full addresses are accurate to within a few meters. ZIP codes and city names give the center point of that area.
- Haversine formula precision — The formula itself is accurate to within about 0.5%. The small margin exists because Earth is slightly flattened at the poles (oblate spheroid), not a perfect sphere.
For most practical uses — coverage analysis, proximity calculations, and distance estimation — the results are highly accurate.
How is this different from driving distance?
Straight-line distance is the direct point-to-point distance, ignoring roads entirely. Driving distance follows actual roads and accounts for highways, turns, and detours.
- Straight-line: 2,451 miles from New York to Los Angeles
- Driving: ~2,790 miles from New York to Los Angeles
Use straight-line distance for coverage areas, proximity filtering, and geospatial analysis. Use driving distance for route planning, ETAs, and mileage tracking.
We offer both: the Straight Line Distance Calculator and the Driving Distance Calculator.
Can I switch between miles and kilometers?
Yes. Select your preferred unit from the dropdown above the input area before clicking Calculate Distances. The tool supports both miles and kilometers. To recalculate with a different unit, simply change the selection and click Calculate again.
How many pairs can I calculate at once?
- Trial users: Up to 10 pairs per batch, 5 batches per day
- Paid subscribers: Up to 100 pairs per batch, unlimited batches per day
If you need more than 100 pairs, split them across multiple batches.
Can I import data from a spreadsheet?
Yes. Click Import CSV / Excel to upload a file with two columns: origin and destination. Supported formats:
- CSV files (.csv)
- Excel files (.xlsx, .xls)
You can also paste directly from Excel or Google Sheets. When you copy two columns, they paste as tab-separated values, which the tool handles automatically.
Why do I need a Google Maps API key?
We use a "Bring Your Own Key" (BYOK) model. Your API key is used to geocode addresses into coordinates via Google's Geocoding API. This approach:
- Keeps our tool pricing low ($19.99/month vs. enterprise rates)
- Gives you full control over your API usage and costs
- Keeps your data private — geocoding requests go directly from our server to Google
Google provides $200/month in free credits, which covers approximately 40,000 geocoding requests per month. Most users never exceed the free credit.
How much does the Google Maps API cost?
Google provides $200/month in free credits for all Google Maps Platform APIs. The Geocoding API costs $5 per 1,000 requests beyond the free tier.
Since the tool deduplicates geocoding (the same address in multiple pairs is only geocoded once), your actual API usage may be less than the total number of addresses entered.
For most users, the free monthly credit covers all geocoding needs.
Is my data secure?
Yes. Your data is handled securely:
- API keys are encrypted using AES encryption before storage
- Geocoding requests go directly to Google Maps — we are the intermediary but do not store your raw queries beyond the calculation history
- Calculation history is private to your account and only accessible when logged in
- All data is transmitted over HTTPS
- We never share, sell, or use your location data
What if an address cannot be geocoded?
If an address fails to geocode, the result row shows an ERROR status with a description. Common reasons:
- Typos or misspelled addresses
- Addresses that don't exist in Google's database
- Very new construction not yet mapped
- Incomplete or overly vague locations
To fix: add more detail to the address (city, state, ZIP), check spelling, or try a nearby location.
Can I access my calculation history later?
Paid subscribers can access all past calculations from the Calculation History section on the tool page. Each entry shows the date, pair count, and results. You can:
- View any past calculation to see the full results
- Download any past calculation as a CSV file
- Browse paginated history (10 entries per page)
Trial users do not have access to saved history.
What export formats are available?
Currently, the tool exports results as CSV (Comma-Separated Values) files with UTF-8 encoding and BOM header for Excel compatibility. The CSV includes all data: addresses, distances, coordinates, and status.
The CSV format works with Excel, Google Sheets, LibreOffice, GIS software (QGIS, ArcGIS), databases, and any application that reads CSV files.