Square Miles to Square Kilometers Converter — Convert mi² to km² (Exact: 1 mi² = 2.589988110336 km²)
Accurate square miles (mi²) to square kilometers (km²) converter using exact definitions: 1 mile = 1609.344 m ⇒ 1 square mile = 2.589988110336 km². Ideal for geography, GIS, conservation reporting, logistics coverage, and market size analysis. Includes precise formulas, step-by-step examples, expanded reference tables, a detailed FAQ, and practical tips.
Exact bases: 1 mi = 1609.344 m ⇒ 1 mi² = 2.589988110336 km². Therefore km² = mi² × 2.589988110336. See all area mertric converters.
About Square Miles to Square Kilometers Conversion
The square mile (mi²) remains common in US media, transportation planning, public safety briefings, and legacy datasets. The square kilometer (km²) is the SI-based standard used by GIS teams, researchers, and international statistics offices. Converting mi² to km² helps you publish figures in a globally recognized unit without sacrificing precision or changing your workflow.
Because the mile is defined exactly—1 mi = 1609.344 m—the area factor is exact: 1 mi² = 2.589988110336 km². Store areas in one canonical unit (often km² for SI workflows), compute the other unit for UI, and round once at display time. This keeps dashboards, maps, PDFs, and CSVs in sync across teams and vendors.
A reliable pattern is to store area_km2 canonically, derive area_mi2 for US-facing interfaces, and include a short “Methods” note—constants, rounding rules, and field names—so every service uses identical math.
Square Miles to Square Kilometers Formula
Exact relationship
Use either expression:
km² = mi² × 2.589988110336
// inverse
mi² = km² ÷ 2.589988110336 (≈ km² × 0.386102158542)Example:
25 mi² × 2.589988110336 = 64.7497027584 km²Related Area Converters
What is a Square Mile (mi²)?
A square mile is the area of a square one mile on a side. With the statute mile fixed at exactly 1609.344 meters, its area equals 2.589988110336 km². Square miles are common in US demographic summaries, transportation studies, and news articles—often reported alongside km² for international context and comparability.
What is a Square Kilometer (km²)?
A square kilometer is the area of a square one kilometer on a side (1000 m × 1000 m). It composes cleanly with other SI units and spatial datasets, which is why it’s preferred by national statistics offices, conservation groups, and GIS practitioners.
Step-by-Step: Converting mi² to km²
- Read the area in square miles (mi²) from your table or map attribute.
- Multiply by 2.589988110336 to convert to square kilometers (km²).
- Round once at presentation based on your policy (e.g., 2–3 decimals for public outputs; more for small polygons).
Example walkthrough:
Input: 4.9 mi²
Compute: 4.9 × 2.589988110336 = 12.690... km²
Output: 12.6900 km² (UI, 4 decimals)Common Conversions
Quick checks (mi² → km²)
| mi² | km² | mi² | km² |
|---|---|---|---|
| 1 | 2.589988110336 | 2 | 5.179976220672 |
| 5 | 12.94994055168 | 10 | 25.89988110336 |
| 25 | 64.7497027584 | 50 | 129.4994055168 |
| 100 | 258.9988110336 | 1000 | 2589.988110336 |
Quick Reference Table
Square kilometers to square miles (km² → mi²)
| km² | mi² | km² | mi² |
|---|---|---|---|
| 1 | 0.386102158542 | 5 | 1.93051079271 |
| 10 | 3.86102158542 | 25 | 9.65255396356 |
| 50 | 19.3051079271 | 100 | 38.6102158542 |
| 250 | 96.5255396356 | 1000 | 386.102158542 |
Frequently Asked Questions
What is the exact formula to convert square miles to square kilometers?
Use the internationally fixed statute mile: 1 mile = 1609.344 meters. Squaring gives 1 mi² = (1609.344 m)² = 2,589,988.110336 m² = 2.589988110336 km². Therefore km² = mi² × 2.589988110336. The inverse is mi² = km² ÷ 2.589988110336 (≈ km² × 0.386102158542). These constants are exact and reproducible across GIS and spreadsheets.
Why is the length factor squared in area conversions?
Area is two-dimensional. A 1D conversion (miles ↔ kilometers) must be squared for area. Since 1 mi ≈ 1.609344 km, then 1 mi² ≈ (1.609344)² km² = 2.589988110336 km². Forgetting to square produces large errors—roughly 1.61× instead of 2.59×—which can materially distort reports and contracts.
Does projection or geodesy affect the mi² ↔ km² conversion?
The unit conversion factor is fixed. However, the *measurement* of an area on Earth depends on your method: planar area in a projected CRS vs. geodesic area on an ellipsoid. Compute area correctly for your geometry (e.g., geodesic for large regions), then apply the same exact unit conversion.
How should I round for dashboards, reports, and press notes?
Keep full precision internally and round once at presentation. For dashboards and press, 2–3 decimals in km² is readable. For scientific and GIS outputs, carry precision to match your data resolution (e.g., to 0.0001 km² for small polygons). Publish a short rounding policy so maps, PDFs, and CSVs consistently agree.
Can I mix mi² and km² in one column when summing or averaging?
Avoid mixing units in the same numeric field. Normalize to a canonical unit (many teams choose km²), perform all math and aggregation, then convert for display. Mixed-unit columns are a common cause of audit discrepancies and off-by-percent errors.
Is a mile here the same as a nautical mile?
No. This page uses the international statute mile (exactly 1609.344 m). A nautical mile is 1852 m and is used for navigation. Land areas reported in square miles should not be confused with nautical square miles.
What precision should I store in my database?
Store full double-precision floats or fixed-point values in a single canonical unit (commonly km²). Round once at the presentation layer. Include a methods note with constants—“1 mi² = 2.589988110336 km²”—and your rounding policy to prevent unintentional changes by downstream services.
How can I regression-test my conversion pipeline automatically?
Maintain known pairs—e.g., 1 mi² = 2.589988110336 km²; 10 mi² = 25.89988110336 km²; 100 km² = 38.6102158542 mi²—and assert both directions in CI. This catches accidental constant edits and double-rounding across layers.
Do I need to account for elevation or slope when converting units?
No. The unit conversion is independent of terrain. If you require *surface* area (over terrain) rather than planimetric area, compute that with GIS first. Once an area value is established, the mi² ↔ km² conversion is the same.
What about very large regions—will curvature change the factor?
The conversion factor itself is fixed. Curvature affects how you *measure* the area, not how you convert between units. Use appropriate geodesic area methods for continents, countries, and ocean polygons, then apply this exact conversion.
Tips for Working with mi² & km²
- Keep SI (km²) canonical for analytics and compliance; compute mi² for US-facing documents. This avoids mixed-unit math and makes data pipelines easier to audit.
- Publish a single rounding policy and apply it uniformly across map labels, PDFs, dashboards, and CSV exports. Round only once on output to prevent drift from double-rounding.
- Use explicit, unit-suffixed field names such as area_km2 and area_mi2. Include a short “Methods” note with constants: “1 mi² = 2.589988110336 km²; inverse 1 km² ≈ 0.386102158542 mi².”
- For large regions, compute geodesic areas in GIS before converting units. Projection choice affects *measurement*, not the unit conversion factor.
- Maintain a small regression table of known pairs and test both directions in CI to catch accidental constant edits.
Where This Converter Is Used
- 🗺️ GIS & cartography: Present areas in km² for international audiences while storing mi² legacy figures.
- 🌿 Conservation & ecology: Protected areas, habitat extents, and wildfire footprints.
- 🏙️ Urban planning: District sizes, service coverage zones, and land-use summaries.
- 🚚 Logistics & ops: Coverage areas, warehouse catchments, and market territories.
- 📰 Media & education: Convert US-centric mi² numbers to km² for global context.