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SESK: Stuff Everyone Should Know · sesk.info/eng-pound-force-to-newtons

About how many newtons are in one pound-force?

About 4.45 N (4.448 222 N to be precise).

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  1. About 4.45 N ✔
  2. About 0.45 N
  3. About 9.81 N

Why: One pound-force is about 4.45 newtons. That is why the Mars Climate Orbiter's thruster effects were underestimated by a factor of about 4.45.

Huh, didn't know that: The kilogram-force is exactly 9.806 65 N, which is where the 9.81 confusion comes from.

The dad joke
I asked for a pound of force and got 4.45 newtons. The exchange rate is brutal.
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References

Answer: About 4.45 N. One pound-force is about 4.45 newtons. That is why the Mars Climate Orbiter's thruster effects were underestimated by a factor of about 4.45.

  1. NIST Guide to the SI (SP 811), Appendix B.9 conversion factors www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b9
    pound-force (lbf)
    Checked 2026-10-11.
  2. NIST Guide to the SI (SP 811), Appendix B.9 conversion factors www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b9
    kilogram-force (kgf) newton (N) 9.806 65 E+00
    Checked 2026-10-11.

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