Feet per Second to kmph Converter - Convert ft/s to kmph
High-quality feet per second (ft/s) to kmph converter using exact constants. Includes step-by-step examples, expanded tables, rigorous rounding guidance, detailed FAQs, practical tips, and structured data.
Exact identity: kmph = (ft/s) × 1.09728 (and ft/s = kmph ÷ 1.09728). See all MetricCalc's online speed converters.
About Feet per Second to kmph Conversion
Many engineering logs and legacy telemetry streams express speed in feet per second (ft/s) because that matches historical instrumentation and U.S. customary practice. Meanwhile, customer-facing products, regulatory filings, and cross-functional dashboards often standardize on kmph to improve clarity for global audiences. This converter implements the exact identity between the two, with a rigorous formatting policy so your results remain reproducible across dashboards, PDFs, and CSV exports.
As a best practice, adopt m/s as your canonical compute unit. Convert to ft/s or kmph only at presentation boundaries, and round once at output. This prevents silent drift when numbers are copied between systems, and it ensures consistent reporting over time.
Feet per Second to kmph Formula
Exact relationship
Use either expression:
kmph = (ft/s) × 1.09728
// inverse
ft/s = kmph ÷ 1.09728SI breakdown:
1 ft = 0.3048 m (exact), 1 m/s = 3.6 km/h (exact)
⇒ 1 ft/s = 0.3048 × 3.6 = 1.09728 km/h (exact) ⇒ kmph matches km/h.Related Speed Converters
What is Feet per Second (ft/s)?
Feet per second is a speed unit indicating how many feet are traveled each second. Because it is tied to the foot, it remains common in U.S. aerospace testing, sports timing (for example, ball exit velocity and sprint splits), and older civil-engineering specifications. Converting ft/s to kmph applies a single linear factor, making it straightforward to align legacy logs with SI-friendly reports.
Typical magnitudes include pedestrian speeds (< 15 ft/s), highway-equivalent speeds (~90–120 ft/s), and sports bursts (> 150 ft/s). Regardless of magnitude, the same factor 1.09728 converts to kmph, ensuring consistency.
What is kmph?
kmph stands for kilometers per hour and is an alternative textual form of the standard symbol km/h. It is widely recognized by non-technical audiences, appears in consumer interfaces, and is common in search queries. In technical writing you may prefer km/h, but kmph conveys the same unit and the same numerical value.
Using kmph can improve discoverability while preserving scientific rigor. In data pipelines, store m/s, then render kmph (or km/h) at the last step using the exact identity to avoid errors introduced by manual conversions.
Step-by-Step: Converting ft/s to kmph
- Read or ingest the speed in ft/s.
- Multiply by 1.09728 to obtain kmph.
- Apply a single rounding step that matches your policy or sensor precision.
- Keep unit symbols explicit in labels, legends, and export headers.
Example walkthrough:
Input: 100 ft/s
Compute: kmph = 100 × 1.09728
Output: 109.728 kmph (UI rounding only)Common Conversions
| Feet per Second (ft/s) | kmph |
|---|---|
| 1 | 1.09728 |
| 5 | 5.4864 |
| 10 | 10.9728 |
| 25 | 27.432 |
| 50 | 54.864 |
| 100 | 109.728 |
| 150 | 164.592 |
| 200 | 219.456 |
| 300 | 329.184 |
| 500 | 548.64 |
Quick Reference Table
| kmph | Feet per Second (ft/s) |
|---|---|
| 5 | 4.558 (≈) |
| 10 | 9.116 (≈) |
| 20 | 18.232 (≈) |
| 30 | 27.348 (≈) |
| 50 | 45.583 (≈) |
| 80 | 72.933 (≈) |
| 100 | 91.134 (≈) |
| 120 | 109.361 (≈) |
| 150 | 136.701 (≈) |
| 200 | 182.268 (≈) |
Precision, Rounding & Significant Figures
Operational rounding
Convert with full internal precision and round once at presentation. Use scientific notation for very small or very large values when helpful; keep the underlying numbers exact for reproducibility and audit trails.
Consistent documentation
Use explicit unit-suffixed fields (speed_fps, speed_kmph, speed_ms) and publish a short methods note listing identities, the inverse, rounding policy, and a few anchor conversions. Add a tiny CI test set to validate both directions continuously.
Where This Converter Is Used
- Aviation and UAV telemetry correlating legacy ft/s feeds with kmph reports for flight summaries.
- Sports science translating instantaneous speeds for broadcasts and coaching tools.
- Wind-tunnel and CFD pipelines that mix Imperial inputs with SI-friendly outputs.
- Compliance and safety reporting that standardizes public documents in kmph.
Frequently Asked Questions
What is the exact formula to convert feet per second to kmph?
Using exact SI-traceable constants, 1 ft = 0.3048 m and 1 m/s = 3.6 km/h. Therefore 1 ft/s = 0.3048 × 3.6 = 1.09728 km/h exactly, and kmph = (ft/s) × 1.09728. The inverse identity is ft/s = kmph ÷ 1.09728. Because these are powers-of-ten and defined constants, no approximation is involved.
Is kmph the same as km/h?
Yes. kmph is a widely used textual shorthand for “kilometers per hour.” Standards bodies and scientific styles favor the symbol km/h, but both represent the same unit. This page uses “kmph” to match the slug and user intent while preserving exact underlying math.
Which unit should I use as the canonical store for speed data?
Store speeds in meters per second (m/s) for computation, then derive ft/s or kmph for display. Centralizing constants and converting at render time prevents silently diverging numbers across services, exports, and dashboards.
How should I round values for dashboards, CSV exports, or reports?
Keep full internal precision and round once at presentation. Choose decimals that reflect sensor resolution or policy (e.g., 2–3 decimals for consumer dashboards, more for engineering analysis). Document your rounding policy alongside constants for auditability.
Can I type scientific notation such as 1.2e2 in the calculator?
Yes. The input accepts typical numeric forms, including scientific notation. Extremely small or large outputs automatically switch to scientific notation to maintain readability without losing significant digits.
Why does the constant 1.09728 appear in ft/s ⇄ kmph conversions?
It comes from chaining two exact definitions: converting feet to meters (0.3048 m per ft) and meters per second to kilometers per hour (×3.6). Multiplying 0.3048 by 3.6 yields 1.09728 exactly.
What anchor pairs should I memorize or add to CI tests?
1 ft/s = 1.09728 kmph; 10 ft/s = 10.9728 kmph; 100 ft/s = 109.728 kmph. For reverse checks: 100 kmph ≈ 91.134 ft/s; 120 kmph ≈ 109.361 ft/s. Anchors help detect formatting or parsing regressions quickly.
Does locale formatting affect the underlying value or only its display?
Only the display. Thousands separators and decimal symbols change with locale, but the stored number and the conversion remain exact. Format for your audience’s locale at render time.
Where do ft/s → kmph conversions show up in practice?
Aviation and UAV test sheets, sports timing (ball exit speed, sprint splits), wind-tunnel studies, and legacy telemetry pipelines that must present SI-friendly values to non-technical audiences.
Is the conversion linear across all magnitudes?
Yes. Speed conversions are linear. Doubling the input in ft/s doubles the output in kmph; the proportionality constant (1.09728) remains the same regardless of magnitude.
What’s a good mental-math approximation?
Multiply ft/s by ~1.1 to estimate kmph quickly. For production systems, use the exact constant 1.09728 and apply a single rounding step at presentation.
How many significant figures should I report?
Match your measurement uncertainty or policy. If a sensor yields 3 significant figures, present 3 after conversion. Avoid re-rounding in downstream processes; round once at the boundary to humans.
How should I name fields in exports and APIs to avoid confusion?
Use explicit unit-suffixed names such as speed_fps, speed_kmph, and speed_ms. Include a short methods note listing identities, the inverse, rounding policy, and a few anchor conversions.
Can I rely on 1.09728 for compliance documents?
Yes. The factor is derived from exact SI-traceable definitions (foot and meter relationship; m/s to km/h). Cite the identity and your rounding policy in the methodology section.
Tips for Working with ft/s & kmph
- Adopt m/s as the compute base; derive ft/s and kmph at presentation.
- Round once at output; never feed rounded UI values back into storage.
- Publish constants plus round-trip anchors; validate both directions in CI.
- Keep unit symbols explicit across legends, labels, and export headers.