Conversion method
Linear momentum is mass times velocity. Impulse (force × time) has the same unit, so 1 N·s equals 1 kg·m/s. Pound foot per second uses the pound as a mass; pound-force second uses the pound-force, which includes standard gravity (9.80665 m/s²). Signs indicate direction along one axis.
lb·ft/s = x × 7.233013851209893
10 kg·m/s = 72.330139 lb·ft/s.
| kg·m/s | lb·ft/s |
|---|---|
| 1 | 7.233014 |
| 5 | 36.165069 |
| 10 | 72.330139 |
| 25 | 180.825346 |
| 50 | 361.650693 |
| 100 | 723.301385 |
Unit definitions and sources
Linear momentum is mass times velocity. Impulse (force × time) has the same unit, so 1 N·s equals 1 kg·m/s. Pound foot per second uses the pound as a mass; pound-force second uses the pound-force, which includes standard gravity (9.80665 m/s²). Signs indicate direction along one axis.
| Unit and system | Use | Definition | Relationship |
|---|---|---|---|
| Kilogram meter per second (kg·m/s); si | Common units | Kilogram meter per second: base (kg-m-s) = value × 1. SI coherent unit of momentum. Common use: Momentum. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Newton second (N·s); si | Common units | Newton second: base (kg-m-s) = value × 1. 1 N·s = 1 kg·m/s² × 1 s = 1 kg·m/s (impulse). Common use: Momentum. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Pound foot per second (lb·ft/s); us | Common units | Pound foot per second: base (kg-m-s) = value × 0.13825495437600002. 0.45359237 kg × 0.3048 m per second = 0.138254954376 kg·m/s exactly. Common use: Momentum. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Pound-force second (lbf·s); us | Common units | Pound-force second: base (kg-m-s) = value × 4.4482216152605. 1 lbf = 0.45359237 kg × 9.80665 m/s² = 4.4482216152605 N, so 1 lbf·s = 4.4482216152605 N·s exactly. Common use: Momentum. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Gram centimeter per second (g·cm/s); si | Specialist units | Gram centimeter per second: base (kg-m-s) = value × 0.00001. 0.001 kg × 0.01 m per second = 1e-5 kg·m/s (CGS). Common use: Momentum. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Dyne second (dyn·s); si | Specialist units | Dyne second: base (kg-m-s) = value × 0.00001. 1 dyn = 1e-5 N, so 1 dyn·s = 1e-5 N·s = 1 g·cm/s. Common use: Momentum. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
Sources: NIST: SP 811 Appendix B.8: conversion factors; BIPM: International System of Units
Precision of momentum conversions
All 6 momentum units convert through Kilogram meter per second (kg·m/s). 6 have an exact defined relationship to the base unit and 0 are conventional or measured values. Results and the tables on this page come from the same engine, so a table value can be checked against the converter directly.
Standard display shows up to six decimal places, switching to scientific notation for very large or small values. Calculation uses JavaScript binary floating point independently of display rounding, so extra digits are not a claim about measurement accuracy. Each unit lists its own source; a citation records where the definition comes from, not an independent review. See Conversion methodology for the review and correction process.