What is a slug?
A slug is the imperial / US engineering unit of mass, created to keep Newton’s second law F = m × a tidy when using pounds-force (lbf) and feet per second squared (ft/s²). One slug is the mass that accelerates at 1 ft/s² when a force of 1 lbf is applied.
Exact conversion we use
1 slug = 14.59390294 kg
This comes from: 1 slug = 32.1740486 lbm and 1 lbm = 0.45359237 kg → 32.1740486 × 0.45359237 = 14.59390294 kg
Formulas
kg = slugs × 14.59390294
slugs = kg ÷ 14.59390294
Why do some sites show slightly different numbers?
Some references round to 14.5939 kg, others to 14.594 kg, and some use slightly different values for standard gravity or the pound-mass. For engineering work it’s best to stick to the full number above.
FAQ
1. Where is the slug actually used?
In older US engineering textbooks, aerospace and mechanical calculations that used imperial units, and in some military/aviation contexts where lbf and ft/s² are still in use.
2. Is a slug a unit of weight?
No, it’s a unit of mass. Weight is a force (lbf or newtons). The slug was defined to keep mass separate from force.
3. Can I convert slugs directly to newtons?
You can convert slugs → kg (with this tool) and then kg → newtons using N = kg × 9.80665 m/s².
Formula (LaTeX) + variables + units
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1 slug = 14.59390294 kg This comes from: 1 slug = 32.1740486 lbm and 1 lbm = 0.45359237 kg → 32.1740486 × 0.45359237 = 14.59390294 kg
kg = slugs × 14.59390294 slugs = kg ÷ 14.59390294
- No variables provided in audit spec.
- NIST — Weights and measures — nist.gov · Accessed 2026-01-19
https://www.nist.gov/pml/weights-and-measures - NIST — SI units — nist.gov · Accessed 2026-01-19
https://www.nist.gov/pml/owm/metric-si/si-units
Last code update: 2026-01-19
- Initial audit spec draft generated from HTML extraction (review required).
- Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
- Confirm sources are authoritative and relevant to the calculator methodology.