Force Converters
Last updated: 2 June 2026
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Guide
Force: From Torque Specs to Engineering Calculations
Your car's manual says to tighten the wheel nuts to 120 Nm (newton metres). You're building a bookshelf and need to anchor it to the wall. A package says it weighs 50 kgf. Engineers throw around newtons (N) and kilogram-force (kgf) like everyone understands them. These are all ways to express force, and confusing them can mean your wheel falls off or your shelf crashes down.
Start with newtons. One newton is the force needed to accelerate 1 kilogram at 1 metre per second squared. This is the SI unit (metric system standard). Most engineers and physicists use newtons. When you're doing physics calculations, newtons is the correct unit. One kilogram on Earth experiences roughly 9.81 newtons of gravitational force (its weight). A 10-kilogram object weighs about 98.1 newtons.
Kilogram-force (kgf) is the force exerted by 1 kilogram of mass under Earth's gravity. It's roughly 9.81 newtons. Some countries and older references still use kgf, particularly in Europe and some Australian engineering standards. It's not official SI, but it persists because it's intuitively simple. A 50 kgf weight pushes down with 50 kilograms of force. Most modern specifications use newtons instead.
Torque is rotational force, measured in newton metres (Nm). When your car's manual specifies "120 Nm", that's the twisting force needed. 1 Nm is the force of 1 newton applied 1 metre away from the pivot point. A 10-newton force applied 2 metres from the pivot creates 20 newton metres of torque. This matters for bike maintenance, car maintenance, and any fastening. Too little torque and the part comes loose. Too much torque and you strip threads or break the fastener.
For car maintenance in Australia, you'll see torque specs in Nm. Wheel nuts are typically 80-120 Nm depending on the vehicle. Cylinder head bolts need careful torque sequences and ranges like 70-80 Nm. If you're using a basic wrench, you're guessing. A torque wrench is worth $40-$80 and prevents expensive mistakes. Buy one that matches your car's likely torque range. Most passenger cars need 20-150 Nm torque wrench.
Pounds-force (lbf) is the imperial equivalent of newton. The US and UK use this, particularly in aviation and older specifications. One pound-force equals about 4.448 newtons. When an American car manual specifies "89 foot-pounds", that's a torque measurement. A foot-pound is 1 pound-force applied 1 foot away from the pivot. Converting between newton metres and foot-pounds is annoying, which is why modern Australian specs just use Nm.
Dynes are tiny. One dyne is one ten-thousandth of a newton. You won't encounter dynes in real life unless you're doing physics lab work or reading old textbooks. Engineering uses newtons. Science uses newtons. Forget dynes exist. Similarly, gram-force (gf) is used in some medical and scientific contexts, but it's not standard. Stick with newtons and kilogram-force, and convert one to the other if needed.
Common Questions
What's the right torque for my car's wheel nuts?
Check your owner's manual. Most Australian cars specify 80-120 Nm. Use a torque wrench set to that exact value. Hand-tight is not the same as properly torqued. Under-torque and the wheel comes loose. Over-torque and you risk stripping the threads or breaking the stud. This is non-negotiable.
What's the difference between a newton and a kilogram-force?
One kilogram pushes down with 9.81 newtons of force under Earth's gravity. So 1 kgf = 9.81 N. Modern engineering uses newtons (SI standard). Some older references and non-English countries use kgf. If you see "50 kgf", that's 490.5 newtons. For Australian engineering, assume newtons unless specified otherwise.
How do I use a torque wrench?
Set the wrench to your target torque (usually marked in Nm). Tighten the bolt slowly. When you reach the correct torque, the wrench clicks or releases. Stop immediately. Don't keep turning. If it doesn't click, you've passed the target. Loosen, reset, and try again. A torque wrench loses accuracy if you crank it past the set point.
Is 120 Nm the same as 120 foot-pounds?
No. 120 newton metres equals about 88.5 foot-pounds. If an American manual says 89 foot-pounds, that's roughly 120 Nm. The confusion here costs money, so double-check which unit your manual uses before applying a torque wrench.
Why does torque matter for fastening?
Correct torque ensures the fastener is tight enough to hold but not so tight it stretches or breaks. It's also critical for pressure distribution. Engine head bolts must be torqued in a specific sequence because uneven torque warps the head and causes leaks. Suspension fasteners need exact torque so the car handles correctly.
What torque wrench do I need for general car maintenance?
Most passenger cars need 20-150 Nm torque range. Budget $40-$100 for a reasonable wrench. Halfords, Supercheap Auto, and Bunnings sell them. Click-type wrenches are most common and reliable. Beam-type is cheaper but harder to read precisely. For motorcycles or bikes, you might want 5-25 Nm range.
How We Verify Our Conversions
Every converter on RefDat uses peer-reviewed conversion factors sourced from the International Bureau of Weights and Measures (BIPM), the National Institute of Standards and Technology (NIST), and the Australian National Measurement Institute (NMI). Temperature formulas follow the ITS-90 international temperature scale. Cooking measurements use Standards Australia definitions (AS 1766) where applicable. We cross-check against multiple authoritative sources and test every calculator both forwards and backwards before publishing. If you spot an error, let us know.