Feet per Second to Kilometer per Second Converter - Convert ft/s to km/s
High-quality feet per second (ft/s) to kilometer per second (km/s) converter using exact SI-traceable identities. Includes worked steps, expanded tables, rounding guidance, detailed FAQs, practical tips, and structured data.
Exact identity: km/s = (ft/s) × 381/1,250,000 (≈ 0.0003048). Reverse: ft/s = (km/s) × 1,250,000/381 (≈ 3280.839895). See all MetricCalc's online speed converters.
About Feet per Second to Kilometer per Second Conversion
Feet per second (ft/s) appears in legacy U.S. telemetry, facility tests, sports timing, and some aerospace archives. Kilometer per second (km/s) is common in orbital mechanics, astrophysics, meteors, and high-speed phenomena. This converter uses an exact SI-traceable identity so your values remain reproducible across dashboards, PDFs, and CSV exports without introducing rounding drift.
Adopt m/s as the canonical compute unit for pipelines. Convert to km/s or ft/s only at presentation edges and round once at output. This minimizes chained rounding and keeps reports consistent over time.
Feet per Second to Kilometer per Second Formula
Exact relationship
Use either expression:
km/s = (ft/s) × 381/1,250,000 (≈ 0.0003048)
// inverse
ft/s = (km/s) × 1,250,000/381 (≈ 3280.839895)SI breakdown:
1 ft = 0.3048 m (exact), 1 km = 1000 m (exact)
⇒ km/s = (ft/s × 0.3048) ÷ 1000 = (ft/s) × 381/1,250,000 (exact)Related Speed Converters
What is Feet per Second (ft/s)?
Feet per second reports the distance in feet traveled each second. It persists in U.S.-centric contexts and some test environments. Its exact link to km/s via powers of ten ensures deterministic conversions suitable for audits and reproducible research.
Typical magnitudes include walking (< 15 ft/s), highway-equivalent (~60–100 ft/s), wind-tunnel peaks (> 150 ft/s), and specialized testing at higher values. Regardless of scale, the same constant 381/1,250,000 applies.
What is Kilometer per Second (km/s)?
Kilometer per second expresses how many kilometers are covered each second. It is favored for high-speed phenomena-orbital velocities, re-entry dynamics, solar wind components-where expressing speeds in km/s keeps values concise. Converting between ft/s and km/s is a linear, exact operation based on SI identities.
When publishing in km/s, accompany tables with constants, rounding policy, and round-trip anchors to accelerate reviews.
Step-by-Step: Converting ft/s to km/s
- Read or ingest the speed in ft/s.
- Multiply by 381/1,250,000 to obtain km/s.
- Apply a single rounding step that matches your policy or sensor precision.
- Keep unit symbols explicit across labels, legends, and export headers.
Example walkthrough:
Input: 1000 ft/s
Compute: km/s = 1000 × (381/1,250,000)
Output: 0.3048 km/s (UI rounding only)Common Conversions
| Feet per Second (ft/s) | Kilometer per Second (km/s) |
|---|---|
| 1 | 0.0003048 |
| 10 | 0.003048 |
| 50 | 0.01524 |
| 100 | 0.03048 |
| 500 | 0.1524 |
| 1000 | 0.3048 |
| 2000 | 0.6096 |
| 5000 | 1.524 |
| 10000 | 3.048 |
| 20000 | 6.096 |
Quick Reference Table
| Kilometer per Second (km/s) | Feet per Second (ft/s) |
|---|---|
| 0.001 | 3.280839895 |
| 0.01 | 32.80839895 |
| 0.05 | 164.0419948 |
| 0.1 | 328.0839895 |
| 0.2 | 656.167979 |
| 0.5 | 1640.419948 |
| 1 | 3280.839895 |
| 2 | 6561.67979 |
| 3 | 9842.519685 |
| 5 | 16404.19948 |
Precision, Rounding & Significant Figures
Operational rounding
Convert with full internal precision and round once at presentation. Use scientific notation for extreme magnitudes; keep underlying numbers exact for reproducibility and audit trails.
Consistent documentation
Use explicit unit-suffixed fields (speed_fps, speed_kms, speed_ms) and publish a short methods note listing identities, the inverse, rounding policy, and anchor conversions. Add a tiny CI test set to validate both directions continuously.
Where This Converter Is Used
- Orbital mechanics and re-entry dynamics where km/s is standard.
- Scientific instruments outputting ft/s but reported for astrophysical contexts in km/s.
- Mixed-unit pipelines that reconcile customary archives with SI-first reporting.
- Compliance exports requiring explicit constants and one-time rounding.
Frequently Asked Questions
What is the exact formula to convert feet per second to kilometer per second?
Using exact definitions, 1 ft = 0.3048 m and 1 km = 1000 m. Therefore km/s = (ft/s × 0.3048) ÷ 1000 = (ft/s) × 381/1,250,000 (exact) ≈ (ft/s) × 0.0003048. The inverse is ft/s = (km/s) × 1,250,000/381 (exact) ≈ (km/s) × 3280.839895.
Are 381/1,250,000 and 1,250,000/381 exact constants?
Yes. They follow from exact SI-traceable definitions (the international foot at 0.3048 m exactly; the kilometer at exactly 1000 m). Chaining these creates exact rational factors with no approximation.
Why present kilometer per second instead of meters per second?
Kilometer per second (km/s) is used in orbital mechanics, astrophysics, and high-velocity phenomena where values in m/s would be unwieldy. Internally, we still recommend storing m/s for computation and converting to km/s or ft/s at presentation.
What unit should be my canonical store for speed?
Use meters per second (m/s). It simplifies equations and aligns with SI-first data pipelines. Convert to ft/s or km/s only at the UI/reporting boundary, and round once at output.
How should I round numbers for dashboards and CSV exports?
Keep full internal precision and round once at presentation. Choose decimals that reflect sensor resolution or policy (e.g., 3–6 decimals for km/s in scientific contexts). Document your policy near constants and examples for auditability.
Can I type scientific notation such as 1.2e3 in the calculator?
Yes. Inputs accept standard numeric forms, including scientific notation. Outputs switch to scientific notation automatically for extreme magnitudes to preserve readability and significant figures.
Is the conversion linear across all magnitudes?
Yes. Speed conversions are linear. Doubling the input in ft/s doubles the output in km/s; the proportionality constant (381/1,250,000) is fixed for all magnitudes.
What anchor pairs should I memorize or add to CI tests?
1 ft/s = 0.0003048 km/s; 100 ft/s = 0.03048 km/s; 1000 ft/s = 0.3048 km/s. Reverse checks: 1 km/s ≈ 3280.839895 ft/s; 0.01 km/s ≈ 32.80839895 ft/s.
Does locale formatting affect the stored precision?
No. Locale changes only the visual separators and decimal symbol. The stored numbers and conversions remain exact. Apply locale formatting at render time for the target audience.
Where does ft/s → km/s show up in practice?
Scientific instrumentation, rocket/space vehicle test data, meteor physics, and high-speed simulation outputs that must co-exist with customary-unit logs.
Any mental-math hack for quick estimation?
Multiply ft/s by ≈0.000305 to estimate km/s. For production software and compliance documents, use the exact factor 381/1,250,000 and round once at presentation.
How should I label fields in exports and APIs to avoid confusion?
Use explicit unit-suffixed names such as speed_fps, speed_kms, and speed_ms. Include a short methodology note listing the identities, inverse, rounding policy, and anchor conversions.
Can I rely on these constants for regulatory filings?
Yes. Cite 1 ft = 0.3048 m (exact) and 1 km = 1000 m (exact). Provide your single-step rounding policy and a short set of round-trip anchors.
Tips for Working with ft/s & km/s
- Prefer m/s for compute; render ft/s or km/s at presentation edges.
- Round once at output; never feed rounded UI values back into storage.
- Publish constants and anchors; validate both directions continuously in CI.
- Keep unit symbols explicit across legends, labels, and export headers.