Kips, kilonewtons and tonnes-force — structural load units
The world's structural codes have never agreed on a single force unit. A working engineer converts kips, kN and tf every review meeting.
Structural loads span roughly four orders of magnitude — from a person's weight (~1 kN) to bridge reactions (~10 MN). Every region picked a convenient middle unit and standardised on it. None of them are SI base units; all are practical.
The exact factors
1 kip = 1000 lbf = 4.4482 kN = 0.4536 tf > 1 kN = 0.2248 kip = 0.1020 tf = 224.8 lbf > 1 tonne-force (tf) = 1000 kgf = 9.8067 kN = 2.2046 kip
Where each is used
kip: US AISC steel design, ACI concrete design, US bridge codes. kN: Eurocode, ISO, most modern texts globally. tf (tonne-force): Latin America, France historically, crane and hoist ratings almost everywhere. lbf: US timber design and small-scale mechanical work.
Worked example — column reaction
A column reaction shows as 450 kN on a European drawing. Reviewing under AISC 360: 450 / 4.448 = 101 kips. As tonne-force for the crane rigging plan: 450 / 9.807 = 45.9 tf. Same number three ways — and mixing them by a factor of 10 (a kip read as a tonne-force) doubles the effective safety factor consumption.
Recap
1 kip ≈ 4.45 kN, 1 tf ≈ 9.81 kN. Always confirm the unit on the drawing title block.
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FAQ
Is a 'kip' related to a 'kilogram'?+
No. 'Kip' is short for kilo-pound (force). A kip is a force; a kilogram is a mass. The confusion is why SI-only codes ban both terms.
What is a metric ton-force in engineering?+
Tonne-force (tf) = 1000 kgf = 9.807 kN. It is a gravitational unit — the weight of a metric ton at standard gravity.
This article was written by The Turbo Unit Converter engineering desk (Applied metrology & engineering units) and last reviewed on 2026-07-20 against NIST SP 811 and the BIPM SI Brochure. Read our full editorial policy.