Acres to Square Kilometers Converter - Convert acres to km² (Exact: 1 acre = 0.0040468564224 km²)
Accurate acres to square kilometers (km²) converter using exact international acre definitions. Ideal for land planning, agriculture, forestry, conservation, real estate, and GIS reporting. Includes exact formulas, step-by-step examples, expanded tables, rounding guidance, detailed FAQs, and practical tips.
Exact factor: 1 acre = 0.0040468564224 km² ⇒ km² = acres × 0.0040468564224. See all agricultural land area converters.
About Acres to Square Kilometers Conversion
The acre (ac) remains a staple in U.S. property listings, ranching, agricultural parcels, and many government datasets. The square kilometer (km²) is the SI-friendly unit for regional planning, conservation, and cross-border analytics. Converting acres to km² makes it easy to communicate with international stakeholders and to consolidate results in a consistent metric system.
Because the constants are exact-1 ac = 4,046.8564224 m² and 1 km² = 1,000,000 m²-you can switch units without introducing rounding drift. A robust practice is to compute polygon areas in m² in your GIS, store canonical values in m², and derive acres, hectares, and km² at the edge for UI and reporting. This prevents double rounding and keeps values aligned across maps, PDFs, emails, and CSV exports.
Acres to Square Kilometers Formula
Exact relationship
Use either expression:
km² = acres × (4,046.8564224 ÷ 1,000,000)
// simplified
km² = acres × 0.0040468564224
// inverse
acres = km² × 247.105381467165Example:
680.53980 acres × 0.0040468564224 = 2.750000 km²Related Area Converters
What is an Acre (ac)?
The international acre is defined as exactly 4,046.8564224 m². It is widely used in U.S. land markets, agriculture, and forestry. While some legacy survey datasets reference the U.S. survey acre, the difference is negligible for most planning and reporting. When in doubt, document the use of the international acre in your methods section.
What is a Square Kilometer (km²)?
A square kilometer is the area of a square 1,000 meters on each side, equal to 1,000,000 m² and exactly 100 hectares. It’s ideal for regional summaries-park systems, habitat extents, watershed units, and land-use classes. Using km² keeps values compact while staying fully interoperable with the rest of the SI system.
Step-by-Step: Converting acres to km²
- Calculate or read the area in acres (ac) from your listing, report, or map.
- Multiply by 0.0040468564224 to convert to square kilometers (km²).
- Round once at presentation (e.g., 2–3 decimals for dashboards; more if required by a legal annex or survey method).
Example walkthrough:
Input: 207.56852 acres
Compute: 207.56852 × 0.0040468564224 = 0.840000 km²
Output: 0.84 km² (UI policy: 2 decimals; store full precision internally)Common Conversions
Everyday quick checks (ac → km²)
| acres | km² | acres | km² |
|---|---|---|---|
| 25 | 0.10117141 | 1,000 | 4.04685642 |
| 50 | 0.20234282 | 2,500 | 10.11714106 |
| 100 | 0.40468564 | 5,000 | 20.23428211 |
| 150 | 0.60702846 | 10,000 | 40.46856422 |
| 250 | 1.01171410 | 25,000 | 101.17141056 |
Quick Reference Table
Square kilometers to acres (km² → ac)
| km² | acres | km² | acres |
|---|---|---|---|
| 0.10 | 24.71053815 | 2.50 | 617.76345367 |
| 0.25 | 61.77634537 | 5.00 | 1,235.52690734 |
| 0.50 | 123.55269073 | 10.00 | 2,471.05381467 |
| 0.75 | 185.32903610 | 25.00 | 6,177.63453667 |
| 1.00 | 247.10538147 | 40.00 | 9,884.21525869 |
Precision, Rounding & Significant Figures
Operational rounding
For public dashboards and press notes, 2–3 decimals in km² are readable and stable. For legal filings or survey summaries, follow your measurement uncertainty and standard. Compute in full precision and round once at presentation to keep maps, PDFs, and exports synchronized.
Consistent documentation
Standardize field names (e.g., area_m2, area_km2, area_ha, area_ac) and keep a short methods note: “Exact constants; 1 ac = 4,046.8564224 m²; 1 km² = 1,000,000 m²; round once at presentation.” This prevents subtle drift as values move between GIS, spreadsheets, and BI tools.
Where This Converter Is Used
- 🌾 Agriculture: Parcel sizes in acres converted to km² for international benchmarking and sustainability KPIs.
- 🌳 Forestry & conservation: Restoration units, burn perimeters, and habitat extents summarized in km².
- 🏞️ Parks & planning: Translating park inventories and master plans from acres into km² for cross-border reporting.
- 🏡 Real estate & appraisal: Listings and valuations presented to global investors who prefer SI units.
- 🛰️ GIS & remote sensing: Rolling up acre-based field data to km² for regional analytics and dashboards.
Frequently Asked Questions
What is the exact formula to convert acres to square kilometers?
Use the international acre: 1 acre = 4,046.8564224 m² (exact) and 1 km² = 1,000,000 m² (exact). Therefore 1 acre = 4,046.8564224 ÷ 1,000,000 km² = 0.0040468564224 km² (exact). In general, km² = acres × 0.0040468564224. The inverse is acres = km² × 247.105381467165.
International acre vs. U.S. survey acre-does it matter here?
This converter uses the international acre (exactly 4,046.8564224 m²), the modern standard in most planning, agriculture, and real-estate contexts. The U.S. survey acre differs by only a few parts per million; unless you’re reproducing legacy geodetic work, the international acre is correct for publishing, budgeting, and compliance.
What unit should I store land area in for analytics?
Store one canonical unit-most teams choose square meters (m²) to keep interoperability with SI. Derive acres, hectares, and square kilometers for reports and user interfaces. Rounding should happen once at presentation to keep maps, PDFs, emails, and CSV exports aligned.
How should I round acres ↔ km² for public dashboards and legal reports?
Compute with full precision and round once on output. For public pages, 2–3 decimals in acres or hectares is typical. For permits and survey annexes, follow the precision dictated by the measurement method and governing standard. Publish one rounding policy and apply it consistently.
Do map projections change the unit factor?
Unit factors are fixed by definition and never change. Projections affect how you calculate the polygon’s area from coordinates. Once you have an area in m² (or km²), converting to or from acres is a pure unit step using exact constants.
How do acres relate to hectares and square miles?
1 hectare = 10,000 m² ≈ 2.47105381467165 acres (exact relationship via m²). 1 square mile ≈ 2.58999 km² ≈ 640 acres. You can bridge acres ↔ hectares precisely using the same m² constants, and acres ↔ square miles using km² as an intermediate.
What field names and documentation avoid unit mistakes across teams?
Use explicit columns like area_m2, area_km2, area_ha, area_ac and include a short methods note: “Exact constants: 1 ac = 4,046.8564224 m²; 1 km² = 1,000,000 m²; round once at presentation.” This eliminates off-by-factor and double-rounding issues.
Tips for Working with acres & km²
- Keep m² canonical; derive ac, ha, and km² for UI and reports.
- Round once at output; avoid re-rounding during exports and multi-step pipelines.
- Use explicit unit columns (area_m2, area_km2, area_ha, area_ac) and publish exact constants in your docs.
- Maintain regression pairs (e.g., 680.53980 ac ↔ 2.75 km²; 100 ac ↔ 0.40468564 km²) and assert both directions in tests.