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Convert Kilometers per Hour to Feet per Second - Speed Converter

This converter transforms a single speed value in kilometers per hour (km/h) to feet per second (ft/s) using the internationally defined relationships between metres and feet. It is intended for quick, repeatable conversions for engineering, reporting, and everyday use.

Results are computed from exact unit definitions (1 km = 1000 m; 1 hour = 3600 s; 1 international foot = 0.3048 m). For high-stakes or regulatory measurements, follow the referenced standards and maintain traceable calibration of measurement instruments.

Updated Nov 2, 2025

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Methodology

Conversion applies exact, standard unit definitions. Kilometres are first converted to metres and hours to seconds to obtain metres per second, then metres are converted to feet using the internationally agreed value of 1 foot = 0.3048 metres.

The tool derives a single multiplicative conversion factor from these exact definitions and applies numeric rounding only at the display stage. For precision-critical work, preserve extra significant digits and document uncertainty per the cited standards.

Worked examples

Example 1: 50 km/h → 50 × 0.911344415 = 45.56722075 ft/s ≈ 45.57 ft/s (rounded to 2 decimals).

Example 2: 0 km/h → 0 ft/s (stationary).

Further resources

Expert Q&A

What is the exact conversion factor from km/h to ft/s?

Using exact definitions (1 km = 1000 m; 1 h = 3600 s; 1 ft = 0.3048 m) the factor is (1000 ÷ 3600) ÷ 0.3048 ≈ 0.911344415. Multiply km/h by this factor to get ft/s.

How accurate are the results from this converter?

The converter uses exact international unit definitions. Numerical results are exact up to floating point limits; displayed values may be rounded. For traceable measurement and reporting follow NIST and ISO guidance and account for instrument uncertainty.

Can I convert from feet per second back to kilometers per hour?

Yes. Use the inverse factor: km/h = ft/s ÷ 0.911344415 (approximately km/h = ft/s × 1.097280254).

When should I worry about calibration or regulatory compliance?

When results are used for safety, legal enforcement, or precise engineering calculations, ensure instruments are calibrated to traceable standards and that you comply with applicable regulations (for example workplace safety rules). Refer to the cited standards for calibration and documentation practices.

What display precision should I use?

Choose precision based on use case: two decimal places are common for display, while engineering analyses may require 4–6 significant digits and documentation of measurement uncertainty.

Are km/h and ft/s SI units?

Kilometres per hour is a commonly used derived unit but the SI base unit for speed is metres per second (m/s). Feet per second is not an SI unit; it is based on the international foot defined in metric terms.

Sources & citations