Kilometer per Second to Feet per Second Converter - Convert km/s to ft/s
Accurate kilometer per second (km/s) to feet per second (ft/s) converter with exact constants, step-by-step examples, expanded reference tables, rounding rules, detailed FAQs, tips, and structured data.
Exact identity: ft/s = (km/s) × 1,250,000/381 (≈ 3280.839895). Reverse: km/s = (ft/s) × 381/1,250,000 (≈ 0.0003048). See all MetricCalc's online speed converters.
About Kilometer per Second to Feet per Second Conversion
Kilometer per second (km/s) is the go-to unit for orbital/astrophysical speeds. Feet per second (ft/s) remains common in certain U.S. datasets, facility tests, and legacy archives. This converter uses exact identities so that your public numbers in ft/s match SI-first analytics without arithmetic drift.
For modeling and controls, keep m/s as the canonical compute unit. Convert to km/s or ft/s at the presentation boundary and round once at output to keep results stable over time and across systems.
Kilometer per Second to Feet per Second Formula
Exact relationship
Use either expression:
ft/s = (km/s) × 1,250,000/381 (≈ 3280.839895)
// inverse
km/s = (ft/s) × 381/1,250,000 (≈ 0.0003048)SI breakdown:
1 km = 1000 m (exact), 1 ft = 0.3048 m (exact)
⇒ ft/s = (km/s × 1000) ÷ 0.3048 = (km/s) × 1,250,000/381 (exact)Related Speed Converters
What is Kilometer per Second (km/s)?
Kilometer per second measures kilometers traversed each second. It keeps values compact for high-speed domains such as escape velocities, interplanetary cruise speeds, and shock front propagation. Because 1 km = 1000 m exactly, conversions to or from SI compute bases are straightforward and exact.
When publishing km/s to ft/s, include constants, rounding policy, and round-trip anchors to streamline reviews.
What is Feet per Second (ft/s)?
Feet per second expresses the number of feet traveled per second. It appears in U.S.-centric contexts and older testing infrastructure. The exact factor 1,250,000/381 makes km/s → ft/s conversion linear and audit-friendly across magnitudes.
Clear labeling (unit-suffixed fields) and one-time rounding help prevent silent divergence between systems.
Step-by-Step: Converting km/s to ft/s
- Read the speed in km/s.
- Multiply by 1,250,000/381 to obtain ft/s.
- Apply a single rounding step aligned to your policy or device precision.
- Label units explicitly across legends, labels, and export headers.
Example walkthrough:
Input: 0.1 km/s
Compute: ft/s = 0.1 × (1,250,000/381)
Output: ≈ 328.0839895 ft/s (UI rounding only)Common Conversions
| Kilometer per Second (km/s) | Feet per Second (ft/s) |
|---|---|
| 0.001 | 3.280839895 |
| 0.005 | 16.40419948 |
| 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 |
| 5 | 16404.19948 |
Quick Reference Table
| 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 |
Precision, Rounding & Significant Figures
Operational rounding
Preserve full internal precision and round once at presentation. For extreme magnitudes, scientific notation keeps values readable while retaining significance. Never store rounded UI numbers as canonical values.
Consistent documentation
Publish constants, the inverse, and example anchors alongside your export schema. Use explicit unit-suffixed field names (speed_kms, speed_fps, speed_ms) and maintain a tiny CI suite for round-trip validation.
Where This Converter Is Used
- Spaceflight telemetry, interplanetary cruise segments, and atmospheric re-entry analysis.
- High-speed facilities and simulations needing customary-unit views for stakeholders.
- Mixed-unit data warehouses that standardize analytics in SI while exposing ft/s for certain audiences.
- Compliance and safety reporting where explicit constants and one-time rounding are required.
Frequently Asked Questions
What is the exact formula to convert kilometer per second to feet per second?
Because 1 km = 1000 m (exact) and 1 ft = 0.3048 m (exact), ft/s = (km/s × 1000) ÷ 0.3048 = (km/s) × 1,250,000/381 (exact) ≈ (km/s) × 3280.839895. The reverse is km/s = (ft/s) × 381/1,250,000 (exact).
Is 1,250,000/381 an exact factor?
Yes. It is a rational number derived from exact definitions (kilometer and international foot). No approximation is involved before your chosen display rounding.
Why might I convert km/s to ft/s?
Some archives, facilities, or legacy instruments still prefer ft/s. Converting from km/s enables consistent reporting across audiences while keeping an SI-first analytical core.
Which unit should I choose for canonical storage?
Store meters per second (m/s). It keeps physics equations simple and reduces conversion steps. Render km/s or ft/s at the UI/report boundary, and round once at output.
How should I round values in public dashboards and CSVs?
Maintain full internal precision and round once at presentation, matching sensor resolution or policy. For km/s values, 3–6 decimals are common in scientific contexts.
Can I paste scientific notation like 3.048e-1 for 0.3048?
Yes. The calculator accepts scientific notation. Extremely small or large outputs switch to scientific notation automatically for readability while retaining significant digits.
Is conversion linear across magnitudes?
Yes. Doubling the input in km/s doubles the output in ft/s; the proportionality constant (1,250,000/381) is fixed.
What anchor values are useful for QA?
0.001 km/s ≈ 3.280839895 ft/s; 0.01 km/s ≈ 32.80839895 ft/s; 0.1 km/s ≈ 328.0839895 ft/s; 1 km/s ≈ 3280.839895 ft/s.
Does locale formatting affect the stored number?
No. Locale affects only the appearance (separators and decimal symbols). The stored value and arithmetic remain exact. Apply locale formatting at render time.
Where does km/s → ft/s conversion appear?
Spaceflight and atmospheric re-entry analyses, high-speed test facilities, meteor physics, and mixed-unit telemetry pipelines.
Any mental-math shortcut for quick checks?
Multiply km/s by ≈3280.84 to estimate ft/s. For production code and filings, use the exact 1,250,000/381 factor and round once at presentation.
How should I name fields in exports and APIs?
Use explicit unit-suffixed names-speed_kms, speed_fps, speed_ms-and include a brief methodology note with constants, inverse, rounding policy, and anchor conversions.
Can I cite these identities in compliance documents?
Yes. Reference 1 km = 1000 m (exact) and 1 ft = 0.3048 m (exact). Provide your single-step rounding policy and a small set of round-trip anchors.
Tips for Working with km/s & ft/s
- Use m/s as the compute base; render km/s or ft/s at the edge.
- Round once at output; avoid multiple rounding stages across the pipeline.
- Publish constants and anchors; run CI round-trip checks to catch regressions.
- Keep unit symbols explicit throughout labels and exports.