Feet per second to Kilometers per hour Calculator

Direct answer

Multiply the entered feet per second value by 1.09727999991222 to express it in kilometers per hour (km/h). This converts foot per second (ft/s) to kilometer per hour (km/h) within the documented speed family.

Variables and formula

• Feet per second (ft/s): the source value measured in foot per second.
• Kilometers per hour (km/h): the same quantity expressed in kilometer per hour.
• Conversion factor: 1.09727999991222 kilometers per hour per foot per second.

Kilometers per hour = Feet per second × 1.09727999991222

The generator emits numeric factors with at most 15 significant digits. Calculator results keep up to 10 significant digits for display; this formatting does not increase the precision of the measurement.

Unit definitions and named variants

Source unit: foot per second (ft/s). One foot per second uses the international foot: 1 ft/s = 0.3048 m/s exactly. Named variant used: International foot per second; not U.S. survey foot per second. Reference: National Institute of Standards and Technology: NIST Handbook 44 (2026), Appendix C: General Tables of Units of Measurement.

Target unit: kilometer per hour (km/h). One kilometer per hour is exactly 1000 m / 3600 s = 5/18 m/s. The canonical kilometer per hour definition is used; no alternate named variant is implied. Reference: Bureau International des Poids et Mesures: The International System of Units (SI), 9th edition, version 4.01; National Institute of Standards and Technology: NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically.

The ft/s-to-km/h direction remains inside the speed quantity; it changes the unit label and numerical scale, not the kind of quantity being measured.

Relationship and precision

This route uses at least one deliberately preserved rounded factor. Treat the displayed factor as an approximation at the precision documented below.

• ft/s relationship: The terminating base factor is exact.
• km/h relationship: The exact factor is the repeating value 5/18. The preserved baseFactor 0.2777777778 is rounded and differs from the exact value by about 2.22×10⁻¹¹ m/s per km/h.

To audit the factor through the family base unit, divide the raw dataset factors 0.3048 by 0.2777777778. The generator emits that quotient once at 15 significant digits as the canonical direct factor 1.09727999991222; runtime calculations do not divide the already-emitted base factors again.

Reproducible example

For 10 feet per second, 10 × 1.09727999991222 = 10.9727999991222 kilometers per hour. Repeating the same multiplication with the stated factor reproduces the displayed conversion before interface rounding.

Directional scale check

Because one foot per second contains 1.09727999991222 kilometers per hour, the target number is larger than the source number for every positive input. Zero maps to zero, while negative inputs are rejected because this family models non-negative magnitudes.

Interpretation

Read the result as kilometers per hour, not feet per second. A value entered as ft/s leaves the calculator labelled km/h; this directional distinction matters even when the two units describe the same speed quantity.

Assumptions and limitations

• Only non-negative speed magnitudes are accepted; use a velocity model when direction or sign matters.
• Mile per hour and foot per second use the international foot and international mile.
• Knot means exactly one international nautical mile per hour; the symbol kn is a CalcMotive display convention because the current SI Brochure notes that no internationally agreed unit symbol exists for the knot.

Common mistakes

• fps may also mean frames per second; here it is only a search alias for feet per second.
• 1 km/h is approximately 0.27778 m/s, not 3.6 m/s; 3.6 is used in the reverse direction.

Continue within the Speed family

See the Speed conversion hub for its five-unit reference table and all 20 directed routes.

• Reverse the direction: Kilometers per hour to Feet per second
• Compare another speed route: Feet per second to Meters per second
• Compare another speed route: Feet per second to Miles per hour
• Compare another speed route: Feet per second to Knots
• Compare another speed route: Kilometers per hour to Meters per second

Assumptions

• The entered value uses feet per second exactly as labelled.
• Only non-negative speed magnitudes are accepted; use a velocity model when direction or sign matters.
• Rounding and measurement uncertainty remain the user's responsibility.

Sources and methodology

CalcMotive publishes the formula and assumptions so you can decide whether the estimate fits your use case. See our methodology standards.

• The International System of Units (SI), 9th edition, version 4.01; Bureau International des Poids et Mesures; accessed Aug 7, 2026
• NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically; National Institute of Standards and Technology; accessed Aug 7, 2026
• NIST Handbook 44 (2026), Appendix C: General Tables of Units of Measurement; National Institute of Standards and Technology; accessed Aug 7, 2026