Speed Converter Tools – Convert mph, km/h (kmph), m/s, knots & ft/s
Welcome to the speed conversion hub—your one place to convert between mph, km/h (kmph), m/s, knots, and ft/s. Every calculator uses exact SI and international definitions with instant results and a consistent, mobile-first interface.
Whether you’re analyzing telematics, flight logs, marine navigation, sports timing, or road signage, unit consistency is critical. Our tools centralize precise constants, perform calculations at full precision, and recommend rounding once on output so your PDFs, dashboards, emails, and CSV exports stay in agreement.
For team workflows, pick a canonical unit (often meters per second for engineering) and derive others for UI and regional preferences. Each page below includes exact formulas, worked examples, and rounding guidance so you can move between unit systems without friction.
MPH to KMPH
Miles per hour to kilometers per hour (km/h = mph × 1.609344).
KMPH to MPH
Kilometers per hour to miles per hour (mph = km/h ÷ 1.609344).
MPH to MPS
Miles per hour to meters per second (m/s = mph × 0.44704).
MPS to MPH
Meters per second to miles per hour (mph = m/s ÷ 0.44704).
MPH to Knots
Statute mph to nautical knots (kn = mph × 0.868976).
Knots to MPH
Knots to miles per hour (mph = kn × 1.150779).
MPH to FPS
Miles per hour to feet per second (ft/s = mph × 1.4666667).
FPS to MPH
Feet per second to miles per hour (mph = ft/s × 0.681818).
KMPH to MPS
Kilometers per hour to meters per second (m/s = km/h ÷ 3.6).
MPS to KMPH
Meters per second to kilometers per hour (km/h = m/s × 3.6).
KMPH to Knots
Kilometers per hour to knots (kn = km/h ÷ 1.852).
Knots to KMPH
Knots to kilometers per hour (km/h = kn × 1.852).
MPS to Knots
Meters per second to knots (kn = m/s × 1.943844).
Knots to MPS
Knots to meters per second (m/s = kn × 0.514444…).
Why Exact Speed Conversions Matter
Small rounding errors compound as values traverse sensors, firmware, apps, and reports. By deriving everything from exact base definitions—mile, foot, kilometer, nautical mile, hour, second—you eliminate drift between telemetry, business logic, and compliance exports. This is especially important in regulated domains (aviation, marine, and automotive) where units must be auditable.
Core Relationships You’ll Use Daily
-
m/s = mph × 0.44704•mph = m/s ÷ 0.44704(exact) -
m/s = km/h ÷ 3.6•km/h = m/s × 3.6(exact, 5/18 and 18/5) -
kn = km/h ÷ 1.852•km/h = kn × 1.852(exact) -
kn = m/s × 3600/1852•m/s = kn × 1852/3600(exact rational) -
ft/s = mph × 1.466666…•mph = ft/s × 0.681818…(exact 22/15 and 15/22) -
kn ≈ mph × 0.868976•mph ≈ kn × 1.150779(derived from exact ratios)
Rounding, Precision & Display Strategy
Keep math at full precision; round once at the presentation or export layer. For consumer cards and dashboards, one decimal in mph/km/h is common. For telemetry and analytics, retain more decimals (2–3) or match sensor resolution. Label columns with explicit units (e.g., speed_mps, speed_kmph) so downstream consumers can trust and transform the data correctly.
Data Modeling & Developer Tips
Choose a canonical unit (m/s is a solid default for physics) and centralize your conversion utilities. Maintain a small regression table of known pairs—like 1 mph = 0.44704 m/s; 1 kn = 1.852 km/h—and test both directions in CI. Avoid mixing units within a single column; normalize on write and compute alternates on demand for UI.
Regional Conventions & Accessibility
Road apps in North America tend to prefer mph; most of the world uses km/h; aviation and marine use knots. Present the local unit while keeping a consistent canonical store. For accessibility, ensure unit labels are visible to screen readers and maintain strong contrast for speed badges and charts.
Common Use Cases
- Telematics & fleet management (m/s or km/h canonical; regional UI in mph or km/h)
- Aviation & marine navigation (knots for wind, heading, and true airspeed)
- Sports timing & biomechanics (m/s for analysis; mph/km/h for broadcast graphics)
- E-commerce product specs (treadmill or scooter speeds in mph and km/h)
- Education & engineering labs (SI-based calculations with exact constants)
Worked Examples
Fleet event: A bus logs 22.2 m/s. Multiply by 3.6 to get 79.92 km/h. For a US dashboard, convert to mph by dividing by 1.609344 to get ≈ 49.67 mph. Display with one decimal; keep full precision in storage.
Marine log: A vessel cruises at 12 kn. Multiply by 1.852 for 22.224 km/h, or multiply by 0.514444… for 6.173 m/s. Use knots in the captain’s report and km/h in fuel analytics.
Track split: An athlete averages 10 m/s. Multiply by 3.6 to get 36 km/h, or divide by 0.44704 to get ≈ 22.37 mph. For broadcast graphics, 36.0 km/h is a clean one-decimal display.
Frequently Asked Questions
What are the exact constants behind these speed conversions?
We use international definitions: 1 mile = 1609.344 m (exact), 1 kilometer = 1000 m (exact), 1 hour = 3600 s (exact), 1 foot = 0.3048 m (exact), and 1 nautical mile = 1852 m (exact). From these follow exact factors such as 1 mph = 0.44704 m/s, 1 km/h = 5/18 m/s (≈0.277777…), and 1 knot = 1852/3600 m/s (≈0.514444…).
Should I store speed in m/s, km/h, or mph?
Pick one canonical unit based on your domain. Many engineering stacks store meters per second (m/s) because it’s SI and composes cleanly with other physics calculations. Consumer apps often store km/h or mph. Whatever you choose, document it and convert at the edges for UI and reports.
Why do aviation and marine apps use knots?
Knots are nautical miles per hour. Because a nautical mile is defined as exactly 1852 meters (derived from the Earth’s geometry), knots integrate cleanly with charts, headings, and wind/current calculations. For road contexts, prefer mph or km/h instead.
How should I round for dashboards and compliance reports?
Compute with full precision internally and round once when you display or export. For consumer cards, whole km/h or one decimal is common. For telemetry and compliance, show 1–2 decimals or match instrument resolution. Avoid double-rounding across layers (UI, API, DB).
Is 1 km/h exactly 0.277777… m/s? Why the repeating decimal?
Yes. 1 km/h equals (1000 m)/(3600 s) = 5/18 m/s, which is an exact rational fraction. In decimal form it repeats. Keep the rational constant in code or compute from base units to ensure precise results and round only at presentation.
What’s the difference between statute miles and nautical miles?
A statute mile is exactly 1609.344 meters and is used for road travel (mph). A nautical mile is exactly 1852 meters and is used at sea and in aviation (knots). Don’t mix them: 1 kn ≈ 1.150779 mph and 1 mph ≈ 0.868976 kn.
How do I sanity-check mph ↔ ft/s quickly?
Remember: 1 mph = 1.466666… ft/s (exact 22/15), so 10 mph ≈ 14.667 ft/s. The inverse is 1 ft/s ≈ 0.681818 mph (exact 15/22). These anchors help you spot misplaced decimals in logs or charts.
Do these speed tools handle acceleration or pace (min/km, min/mi)?
This category focuses on speed units only. Pace and acceleration require different formulas and will live in dedicated tools. Keeping scopes small avoids confusion and allows deeper guidance for each topic.
What about the US survey foot—does it affect fps conversions?
Modern systems standardize on the international foot (0.3048 m exact). Unless you process historic survey datasets, you should use the international definitions provided here for consistent fps conversions.
How should I name fields for analytics and exports?
Prefer explicit, unit-suffixed fields like speed_mps, speed_kmph, speed_mph, and speed_kn. Include a short methods note: “Exact constants, round once at output.” This prevents mismatches across dashboards, emails, and CSVs.
Any accessibility and i18n tips for speed displays?
Use locale-aware number formatting for decimals and thousands separators, and always show the unit symbol beside the number. Ensure adequate color contrast for speed badges and avoid unit icons that aren’t announced by screen readers.
Can I mix km/h and mph in the same table column?
Avoid mixing. Normalize to a canonical unit and derive other units for the UI. If you must display mixed inputs, include a units column and normalize in your data model to prevent computations on heterogeneous units.
Keep This Page Handy
Bookmark this category page for rapid access to every speed converter on MetricCalc. As we expand the library, new tools will follow the same layout and rounding philosophy so you can switch unit systems without friction. If a pair is missing, tell us and we’ll build it to the same exacting standards.