Convert Square Feet to Square Kilometers - Area Converter
Convert area values from square feet (sq ft) to square kilometers (sq km) using SI-consistent definitions. This tool applies the internationally accepted relationships between the foot, metre, and kilometre so results are compatible with scientific and regulatory reporting.
The underlying definition used is that 1 foot = 0.3048 metres exactly (by international agreement). From that exact definition the area relationship follows, enabling repeatable conversions for engineering, land measurement, reporting, and data exchange.
Interactive Converter
Convert between square foot and square kilometer with precision rounding.
Quick reference table
| Square Foot | Square Kilometer |
|---|---|
| 1 ft² | 0 km² |
| 5 ft² | 0 km² |
| 10 ft² | 0 km² |
| 25 ft² | 0 km² |
| 50 ft² | 0 km² |
| 100 ft² | 0 km² |
Methodology
Start from the exact definition: 1 foot = 0.3048 metres (internationally defined). Square that linear relationship to express one square foot in square metres: 1 sq ft = (0.3048 m)² = 0.09290304 m².
Convert square metres to square kilometres by dividing by 1,000,000 because 1 km = 1,000 m and therefore 1 km² = 1,000,000 m². Combining these steps gives the conversion from square feet to square kilometres.
For high-volume or programmatic uses, use the exact chained definition above rather than a rounded factor to avoid cumulative rounding error. When publishing results, follow the significant-figure or rounding rules required by your regulatory or data consumer context.
Worked examples
Example 1: 1,000 sq ft → 1,000 × 9.290304e-8 = 9.290304e-5 sq km.
Example 2: 435,600 sq ft (one US survey section) → 435600 × 9.290304e-8 = 0.040468564224 sq km (rounded per context).
When converting very large or very small areas, present results with appropriate significant figures or scientific notation to preserve clarity (for instance, 2.5e-4 sq km).
Expert Q&A
Is the conversion factor exact?
Yes. Because 1 foot is defined exactly as 0.3048 metres by international agreement, the derived factor 1 sq ft = 9.290304e-8 sq km is exact to the precision of that definition. Use the exact chained definitions for highest accuracy.
How many significant digits should I display?
Choose significant digits based on the measurement uncertainty of the source value and the reporting requirements of your audience or regulator. For engineering and scientific work, keep at least as many significant digits as present in the original measurement; for public reporting, round to the usual readable precision (for example, 3–6 significant digits).
Does this conversion account for local surveying definitions (US survey feet)?
This converter uses the international foot (1 ft = 0.3048 m exactly). If you require conversions based on the US survey foot or other legacy definitions, convert from that linear definition first and then square it; check relevant land-survey documentation or national mapping agency guidance when exact legacy-unit handling is required.
How should I report converted area in official submissions?
Follow the unit and rounding rules specified by the receiving agency (for example, cadastral authorities, environmental regulators, or statistical offices). Where available, cite the SI definitions (NIST/BIPM) used and include the number of significant digits or rounding method applied.
Can I convert very large datasets without losing precision?
Yes — perform conversions using double-precision arithmetic (or arbitrary-precision libraries when needed) and avoid intermediate rounding. Export results in a format that preserves numeric precision (CSV, JSON with numeric fields) and document the conversion factor used.
Sources & citations
- NIST — The International System of Units (SI) and unit definitions — https://physics.nist.gov/cuu/Units/
- Bureau International des Poids et Mesures (BIPM) — SI Brochure and unit definitions — https://www.bipm.org/en/publications/si-brochure
- MIT OpenCourseWare — reference materials on units, dimensions, and conversions — https://ocw.mit.edu