Force conversion starts with the newton
The newton is the SI coherent unit of force: the force that gives one kilogram an acceleration of one meter per second squared. CalcOS converts each supported force through newtons.
Force and mass are different quantities. Kilograms and pounds are mass units; kilogram-force and pound-force are force units defined using standard acceleration.
Common force definitions
| Unit | Newton relationship | Definition basis |
|---|---|---|
| dyne | 10⁻⁵ N | CGS exact |
| gram-force | 0.00980665 N | standard gravity |
| kilogram-force | 9.80665 N | standard gravity |
| ounce-force | 0.27801385095378125 N | avoirdupois + standard gravity |
| pound-force | 4.4482216152605 N | avoirdupois + standard gravity |
| kip | 1,000 lbf | structural engineering |
Mass is not force
Mass describes inertia and does not depend on local gravity. Weight is a force. CalcOS never converts a kilogram directly to a newton without an acceleration assumption; kilogram-force is a separately defined conventional force unit.
Ton-force must name its basis
A short ton-force is 2,000 lbf, a long ton-force is 2,240 lbf, and a metric tonne-force is 1,000 kgf. CalcOS exposes all three names and rejects an unlabeled “ton-force.”
Authoritative references: BIPM SI Brochure and NIST SP 811 Appendix B.9.