Converts a speed between m/s, km/h, mph, knots, and ft/s using exact NIST SP 811 length and time definitions.
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Inputs
value (number, from_unit, required) : The speed to convert
from_unit (string, required) one of: m_s, km_h, mph, knot, ft_s : Unit of the input value
to_unit (string, required) one of: m_s, km_h, mph, knot, ft_s : Unit to convert into
Outputs
result (to_unit): The converted speed
Steps
Look up the exact meters-per-second equivalent of from_unit and of to_unit.
Convert the input to m/s: mps = value * ms_per(from_unit).
Convert m/s to the target unit: result = mps / ms_per(to_unit).
Round result to 6 significant figures.
Constants
m_s = 1 m/s (source: Guide for the Use of the International System of Units (SI))
km_h = 0.2777777777777778 m/s (source: Guide for the Use of the International System of Units (SI))
mph = 0.44704 m/s (source: Guide for the Use of the International System of Units (SI))
knot = 0.5144444444444445 m/s (source: Guide for the Use of the International System of Units (SI))
ft_s = 0.3048 m/s (source: Guide for the Use of the International System of Units (SI))
Sources
Guide for the Use of the International System of Units (SI) (National Institute of Standards and Technology, 2026-09-30T19:29:48Z) - km/h = 1000 m per 3600 s; mph = 1609.344 m per 3600 s; knot = 1852 m per 3600 s; all exact ratios.