Convert Miles per Hour to Meters per Second - Speed Converter
This converter converts a speed value in miles per hour (mph) to metres per second (m/s) using the internationally agreed unit definitions. It is suitable for quick checks, engineering estimates, and unit-standardized reporting.
The conversion uses the exact international relationship between the mile and the metre, so the mathematical factor is exact. Practical accuracy depends on the precision of your input and the measurement uncertainty of any instrument used to obtain that input.
Guidance on rounding, significant figures, and calibration is provided below so you can choose an appropriate level of precision for driving, laboratory, and industrial contexts.
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Methodology
Underlying standard: the international yard and mile definitions and the SI metre are used as the authoritative basis for unit values. The tool applies the exact numeric relationship derived from those definitions.
Precision and reporting: for everyday use (legal speed, driving) two decimal places are usually sufficient; for engineering, fluid dynamics, or instrumentation use retain more significant figures and include measurement uncertainty per ISO and NIST guidance.
Calibration and compliance: if converting measured speeds for regulatory, safety, or contractual purposes, record instrument calibration traceable to an accredited laboratory following ISO/IEC 17025 and document uncertainty estimates according to NIST and ISO best practices.
Worked examples
Example 1: 60 mph → 60 × 0.44704 = 26.8224 m/s (commonly reported as 26.82 m/s).
Example 2: 5 mph → 5 × 0.44704 = 2.2352 m/s (commonly reported as 2.24 m/s).
Expert Q&A
Is the conversion factor exact or approximate?
The numeric factor 0.44704 derives from the exact international definition 1 mile = 1609.344 metres and 1 hour = 3600 seconds, so the factor itself is exact. Practical results are affected only by input precision and instrument uncertainty.
How many decimal places should I use?
For everyday speed reporting (road speeds) two decimal places are typically adequate. For engineering, physics, or instrumentation use retain more significant figures and include uncertainty estimates; consider 4–6 significant figures where required.
What about measurement uncertainty and calibration?
When converting measured speeds for compliance, safety, or contractual records, use calibrated instruments traceable to an accredited lab (ISO/IEC 17025). Report converted values with the original measurement uncertainty propagated to the new units per ISO and NIST guidance.
Can I convert back from m/s to mph?
Yes. To convert from metres per second to miles per hour divide by 0.44704 (equivalently multiply by 3600 / 1609.344 = 2.2369362920544...).
Are there regulatory standards that govern unit use?
Yes. Use the International System of Units (SI) as described by the BIPM and ISO for scientific and many regulatory contexts; national agencies and industry standards bodies provide additional guidance on reporting and traceability.
Sources & citations
- NIST Special Publication 811, Guide for the Use of the International System of Units (SI) — https://www.nist.gov/pml/special-publication-811
- BIPM, The International System of Units (SI Brochure) — https://www.bipm.org/en/publications/si-brochure
- ISO 80000 series — Quantities and units — https://www.iso.org/standard/64973.html
- ISO/IEC 17025 — General requirements for the competence of testing and calibration laboratories — https://www.iso.org/standard/66912.html
- NIST reference on the international mile and unit definitions — https://physics.nist.gov/cuu/Units/mile.html