Scalar magnitude · exact definitions · no Mach shortcut

Linear Speed-Magnitude Unit Converter

Convert one nonnegative scalar speed magnitude between metre/second, kilometre/hour, mile/hour, foot/second, foot/minute and knot.

Exact unit definitionsPoint or commaNo contextual speed claims

Unit conversion only. Direction is not represented, so this is not a vector-velocity calculator. Mach number is not a speed unit and is excluded: it is a ratio to the local speed of sound, which depends on the medium and thermodynamic state. Surface speed, vibration velocity and engineering limits also require separate inputs and scope.

Quantity and traceability

Speed magnitude nonnegative; zero is valid

Input unit

Measurement / calculation record ID

Quantity definition and scalar-magnitude basis

Source value, instrument or model

Input uncertainty and reporting precision

Unit-definition source and revision

Owner / reviewer

Review date

Notes and exclusions Optional: direction handled elsewhere, coordinate frame, measurement bandwidth, environmental state, intended rounding

The input is a nonnegative scalar speed magnitude. A signed vector component or full velocity vector requires direction/coordinates and is not reconstructed here.
“Foot” and “mile” mean the international definitions used by NIST, not legacy US survey units; “knot” means exactly one nautical mile per hour.
No Mach number, local speed of sound, RPM-to-surface-speed, vibration severity or ISO 20816/21940 result will be inferred from this scalar conversion.
Displayed digits do not improve the uncertainty or significant figures of the source value; final reporting will follow the controlled uncertainty record.

Converted scalar magnitude

metre per second

kilometre per hour

mile per hour

foot per second

foot per minute

knot

Conversion method and definitions

v_m/s = x · f_input
y_unit = v_m/s / f_unit

Jednotka	Factor f to m/s	Definition used
m/s	1	coherent SI speed unit
km/h	1000/3600 = 5/18	1 km = 1000 m; 1 h = 3600 s
mph	1609.344/3600 = 0.44704	international mile = 1609.344 m
ft/s	0.3048	international foot = 0.3048 m
ft/min	0.3048/60 = 0.00508	international foot; minute = 60 s
kn	1852/3600 = 0.514444444444…	nautical mile = 1852 m; knot = nautical mile per hour

These are unit-definition conversions, not an empirical formula and not an ISO 21940 balancing calculation. The implementation retains the exact rational/defined factors in binary floating arithmetic and rounds only the displayed decimal text.

Model boundary and removed unsupported content

No fixed Mach conversion. The former page treated Mach as 343.21 m/s and used a linear temperature shortcut. Mach is dimensionless and needs the local acoustic speed for the actual gas composition and thermodynamic state.
No speed/velocity conflation. A scalar magnitude can be converted between units; direction and coordinate frame cannot be recovered.
Exact knot factor. The former code used 0.514444 m/s, truncating the exact 1852/3600 definition. The calculation now retains 0.514444444444….
No contextual lookup table. Walking, running, road, aircraft and light-speed examples were unnecessary and context-dependent.
No unrelated machinery claim. RPM-to-surface-speed and vibration RMS/peak/severity require diameter, frequency/content and standard scope; they are not unit conversions.
No hidden state. Defaults, presets, URL mutation, auto-calculation, clipboard output and dynamic FAQ HTML were removed.

Source traceability

Claim	Klasifikace	Evidence
SI minute/hour definitions; nautical mile = 1852 m; knot = 1852/3600 m/s.	International metrology authority; current SI Brochure	BIPM SI Brochure, 9th ed., v4.01 (2026), Table 8
International-foot basis and velocity conversion factors for ft/s, ft/min, km/h, knot and mph.	Official public metrology guidance	NIST SP 811 Appendix B.9
ISO 80000-3:2019 covers space/time quantity names, symbols, definitions, units and some conversions; Edition 2 confirmed 2023 with Amendment 1:2025.	Official ISO status/scope card; exact content licensed	ISO 80000-3:2019 + Amd 1:2025

Accessed: 15 July 2026. Exact ISO quantity-definition clauses and amendment text remain NEEDS_LICENSED_SOURCE; the public BIPM/NIST definitions are sufficient for the implemented arithmetic.

Published reference examples

By BIPM’s definition, 1 kn = 1852/3600 m/s = 0.514444444444… m/s and exactly 1.852 km/h. By the international-mile definition, 1 mph = 0.44704 m/s and exactly 1.609344 km/h.

Questions

Why is Mach absent?

Mach is a dimensionless ratio v/a, not a fixed speed unit. The local acoustic speed a changes with medium composition and thermodynamic state.

Can I enter a negative velocity component?

No. This worksheet converts a nonnegative scalar magnitude. A signed component must retain its axis, coordinate frame and sign convention in a vector-aware record.

Does conversion change measurement accuracy?

No. More displayed digits do not create information. Apply the uncertainty and significant figures of the source record to the final reported value.