Newtons, kilogram-force, pound-force, poundals and kip — with mass kept in its own panel, because turning a mass into a force needs a gravity and the answer changes with it.
Who this is for: A load chart marked “kg”, or a “ton” that could be three different forces.
Calculator
Try:
1 kilogram-force
9.8067 N
Every figure below is exact rather than measured — each unit is defined against the newton by a chain of definitions, not by an experiment.
The same force in every unit
Force units, converted from your figure
Unit
Value
What it is
newton
9.8067
The SI unit — one kilogram accelerated at one metre per second squared.
kilonewton
0.009807
A thousand newtons. Structural loads are usually quoted here.
meganewton
9.8066e-6
A million newtons — rocket thrust and press capacities.
millinewton
9,806.65
A thousandth of a newton. Contact forces and small springs.
kilogram-force
1.0000
The weight of one kilogram under standard gravity. Exactly 9.80665 N — often written just "kg".
gram-force
1,000.0000
A thousandth of a kilogram-force. Still used for string tension and small springs.
pound-force
2.2046
The weight of one pound under standard gravity. Exactly 4.4482216152605 N.
ounce-force
35.2740
A sixteenth of a pound-force. Common on small load cells and stylus tracking figures.
kip
0.002205
A thousand pound-force. The working unit of US structural engineering.
poundal
70.9316
One pound-mass accelerated at one foot per second squared. 32.174 to the pound-force.
dyne
980,665.00
The CGS unit — one gram accelerated at one centimetre per second squared. Exactly 10⁻⁵ N.
ton-force (short, US)
0.001102
2000 pound-force. The default "ton" in US practice.
tonne-force (metric)
0.001000
1000 kilogram-force. 10.2% above the short ton-force.
ton-force (long, UK)
0.000984
2240 pound-force. 12% above the short ton-force, and it shares its abbreviation.
Two rows share the abbreviation tonf. The short ton-force is 2000 lbf and the long is 2240, so the long is 12% larger under the same three letters — and the metric tonne-force sits between them at 10.2% above the short.
Mass is a different quantity
Weight686.4655 N154.3236 lbf
In kilogram-force70.0000 kgfequal to the mass, by definition
The same 70 kg, weighed in different places
Place
Local g
Weight
Standard gravity (defined)
9.80665 m/s²
686.4655 N
Mount Huascarán, Peru
9.7639 m/s²
683.4730 N
Sea level at the equator
9.7803 m/s²
684.6210 N
Singapore
9.7761 m/s²
684.3270 N
New Delhi
9.7912 m/s²
685.3840 N
London
9.8158 m/s²
687.1060 N
New York
9.802 m/s²
686.1400 N
Sea level at the pole
9.8322 m/s²
688.2540 N
Arctic Ocean surface
9.8337 m/s²
688.3590 N
The mass never changed. Real gravity spans 0.71% across these places, so the weight did. The kilogram-force is defined against a fixed 9.80665 m/s² precisely so that it does not move with location — which makes it a unit of force that behaves like a unit of mass, and is the source of most of the confusion around it.
What that costs a scale
A spring scale reads69.717 kg−0.283 kg
A spring scale measures force and divides by the gravity it was calibrated for, so moving it changes the reading while the mass stays put. A balance does not, because it compares two weights in the same field. This is not a curiosity: legal-for-trade scales in most jurisdictions must be adjusted for the gravity zone they are installed in, and the paperwork exists because the 0.71% span is larger than the tolerance they are held to.
Two imperial systems, and the constant between them
Consistent unit systems in imperial force and mass
System
Mass
Force
Constant needed
Pound-mass and poundal
lbm
pdl
none
Slug and pound-force
slug
lbf
none
Pound-mass and pound-force
lbm
lbf
g_c = 32.1740
One pound-force is 32.1740 poundals, and one slug is 14.5939 kg — which is 32.1740 pounds. The same number twice, because g_c is just standard gravity expressed in feet per second squared. Neither system needs it internally; the constant appears only when a formula uses the pound as a mass and as a force at once, which is what practice actually does. One pound-force is 4.4482216153 N, and that figure is exact.
What this converter covers
Every factor here is exact by definition rather than measured — and the three different tons-force are listed apart rather than merged.
Newtons, kilonewtons, kgf, gf, lbf, ozf, kip, poundal and dyne
All three tons-force, separated rather than merged
Mass to weight under a stated local gravity
What a scale calibrated in one place reads in another
The two consistent imperial systems and the g_c between them
Mass kept apart Three tons-force Exact factors Real local gravity
1 kgf = 9.80665 N · 1 lbf = 0.45359237 × 9.80665 N · g_c = 32.174 lbm·ft/(lbf·s²)
Scenario support
A 500 kgf load is 4903 N · 1 tonf is 8896 N in the US and 9964 N in the UK
A kilogram is not a kilogram-force
A kilogram is an amount of matter. A kilogram-force is what that matter pushes down with, and it equals 9.80665 newtons exactly. They are different quantities, and writing both as “kg” is so common that a crane chart, a torque wrench and a bathroom scale can all be marked identically while meaning two different things.
The distinction is easy to state and easy to lose. A hoist rated at “500 kg” is rated for a force of 500 kgf, which is 4903 N. A parcel marked 500 kg has a mass of 500 kg, and its weight depends on where it is. On Earth those two coincide closely enough that nothing goes wrong — which is exactly why the habit survives, and why it fails only in the situations where failing is expensive.
What each unit actually measures
Written
Quantity
Changes with location?
kg
Mass
No
kgf (often written kg)
Force
No — it is defined against fixed gravity
N
Force
No — but the weight it measures does
lb
Mass
No
lbf (often written lb)
Force
No — same fixed-gravity definition
The middle row is the odd one and the reason the confusion persists. The kilogram-force is a unit of force whose numerical value does not move with location, because its definition pins gravity at 9.80665 rather than using the local value. So it behaves like a mass unit while being a force unit, and the two can be swapped in conversation for years without anything going wrong.
Standards bodies would rather it went away — NIST explicitly deprecates the kilogram-force — and it has not, because a great deal of installed equipment and a great many national codes are written in it. The practical position is to know which one a number means, and to notice that a chart quoting both “kg” and “N” has already made the choice for you.
The pound is used twice, and 32.174 is the bill
The imperial system has the same problem in a sharper form: the pound is used as a unit of mass and as a unit of force, and the two uses are a factor of 32.174 apart when you try to put them in one equation.
There are two ways out of it, and both work perfectly well on their own. Treat the pound as a mass, and F = ma gives you a unit of force called the poundal — one pound-mass accelerated at one foot per second squared. Treat the pound as a force, and the corresponding mass unit is the slug, which is 32.174 pounds. Neither system needs a conversion constant, because each is internally consistent.
Three ways to use the pound, and what each costs
System
Mass unit
Force unit
Constant in F = ma
Absolute
pound-mass
poundal
None
Gravitational
slug
pound-force
None
Engineering
pound-mass
pound-force
g_c = 32.174
Practice uses the third row, because engineers want to say “pounds” for both and are not going to stop. The price is the constant g_c, which appears in thermodynamics and fluid mechanics texts and looks entirely arbitrary until you notice what it is: standard gravity expressed in feet per second squared. 9.80665 divided by 0.3048 is 32.174. It is not a new physical constant, it is a unit conversion wearing a disguise.
Once that is seen, the slug stops being mysterious too. A slug is the mass that one pound-force accelerates at one foot per second squared, so it has to be 32.174 pounds — the same number, for the same reason. Both are the price of using one word for two quantities, paid in a different currency each time.
Three tons-force, two abbreviations
A press rated at “20 tons” is rated at one of three different forces depending on who wrote the plate, and two of the three share an abbreviation.
The three tons-force, and the spread between them
Name
Definition
In newtons
Above the short
Short ton-force (US)
2000 lbf
8896.4
—
Tonne-force (metric)
1000 kgf
9806.7
10.2%
Long ton-force (UK)
2240 lbf
9964.0
12.0%
Twelve per cent is not a rounding difference. On a 20-ton press it is the difference between 178 kN and 199 kN, and on a lifting plan it is the difference between a comfortable margin and none. The short and long tons both abbreviate to tonf, so the abbreviation cannot disambiguate them — only the origin of the document can.
The metric tonne-force is the one that behaves. It is 1000 kgf, so it is exactly 9806.65 N, and it is normally written tf rather than tonf. The useful habit is to read the spelling: “tonne” with an -ne is metric, “ton” without is one of the other two, and which one depends on whether the document is American or British.
This converter lists all three separately for that reason. Collapsing them into a single “ton” row would produce a confident answer that is wrong for two of the three readings of the input.
Standard gravity is a definition
9.80665 m/s² is not gravity anywhere in particular. It was fixed by resolution in 1901 as a conventional value, and it stays fixed while the actual field varies — weaker at the equator, where rotation and the planet’s bulge both work against it, and stronger towards the poles.
Local gravity across the inhabited range
Place
g (m/s²)
Against standard
Mount Huascarán, Peru
9.7639
−0.43%
Singapore
9.7761
−0.31%
Sea level, equator
9.7803
−0.27%
New Delhi
9.7912
−0.16%
New York
9.8020
−0.05%
London
9.8158
+0.09%
Arctic Ocean
9.8337
+0.28%
End to end that is 0.71%. Small, and larger than the tolerance a legal-for-trade scale is held to, which is why weighing regulations in most countries require an instrument to be adjusted for the gravity zone it is installed in. A scale calibrated in London and shipped to Singapore reads about 0.4 kg light on a 100 kg load, and that is a commercial problem rather than a physics curiosity.
The mechanism is worth having straight. A spring scale measures force and divides by the gravity it was told to assume, so moving it changes the answer. A balance compares the unknown against a reference in the same field, so the gravity cancels and the reading holds anywhere. That is the reason precision laboratories still keep balances, and the reason a set of calibration weights travels well while a scale does not.
When the distinction actually bites
Most of the time the mass/force ambiguity costs nothing, and the honest thing to say is which situations are the exceptions.
Bolt torque specifications. Often written kgf·m or N·m, and the numbers differ by 9.8. A figure of “10” is a wildly different tightening depending on which was meant, and there is no way to tell from the number alone — only from the unit, which is exactly the thing that gets dropped when a specification is transcribed.
Anything leaving Earth. Spacecraft and aircraft mass budgets are in kilograms and their loads are in newtons, and the coupling between them changes with the acceleration environment. This is the one setting where collapsing the two quantities is not merely untidy but wrong from the start.
Load cells and test rigs. A cell reading “kg” is almost always reporting kgf and has usually been calibrated against a dead weight at a stated gravity. Feeding that number into a calculation in newtons without the 9.80665 is a factor-of-ten class error that will not look like one.
Structural work across the Atlantic. Kip and kN differ by 4.45, and both are abbreviated in ways that look similar in a hurried drawing. Add the three tons and there are five plausible readings of a load figure on a mixed-origin drawing set.
Where none of those apply — everyday weights, shipping, cooking, most of engineering conversation — the distinction can be left alone with a clear conscience. Knowing where the exceptions are is more useful than being rigorous everywhere.
Related calculators
Other mechanical units where the same distinctions matter:
TorqueNewton-metres, pound-feet, pound-inches and kgf·m — with inch-pounds and foot-pounds named apart, since they differ by twelve.
Pressurepsi, bar, kPa, atm, torr and mmHg — plus why gauge and absolute differ by an offset that no factor can bridge.
EnergyJoules, kilojoules, calories, food Calories, kWh, BTU and therms — with the two calories listed apart, since one is a thousand of the other.
PowerWatts, kilowatts, horsepower and BTU per hour — with mechanical and metric horsepower listed apart, since they differ by 1.4% under one word.
Densitykg/m³, lb/ft³, lb/in³ and lb/gal, with specific gravity against any water reference and the API scale that runs backwards.
Every factor on this page is exact rather than measured, and that is worth saying because it is unusual. The pound has been exactly 0.45359237 kg since 1959 and standard gravity has been exactly 9.80665 m/s² since 1901, so the pound-force is exactly 4.4482216152605 N — a product of two definitions, with no experimental uncertainty in it at all. The one number on this page that is measured, and varies, is local gravity.
SI Brochure, 9th edition — the newton and the coherent derived unitsBureau International des Poids et Mesures · verified 2026-09-07 · The newton as kg·m/s² and the SI position that mass and force are separate quantities — the distinction every conversion on this page rests on
NIST Special Publication 811 — Guide for the Use of the International System of UnitsNational Institute of Standards and Technology · verified 2026-09-07 · The exact conversion factors for pound-force (4.448 221 615 260 5 N), kilogram-force (9.806 65 N) and poundal, and NIST’s explicit deprecation of using the kilogram-force as a unit of force
Resolution 2 of the 3rd CGPM (1901) — the value of standard gravityConférence Générale des Poids et Mesures · verified 2026-09-07 · That gₙ = 9.806 65 m/s² is a defined conventional value rather than a measurement of gravity anywhere — the fact that makes the kilogram-force fixed while real weight is not
Conversion note
The conversions here are exact, but the engineering judgement around them is not something a converter can supply. Load ratings on lifting equipment, fasteners and structures are not simply forces — they carry a safety factor, a duty cycle and an assumed direction of loading, and converting the number without carrying those conditions across is how a correctly converted figure becomes an unsafe one. The local gravity values are representative figures for the named places rather than surveyed values for any particular site; real gravity also varies with altitude and local geology, and a laboratory needing a true figure measures it rather than looking it up. The scale-reading panel models an ideal spring scale and ignores temperature drift, linearity and the buoyancy of air, all of which matter at the precision where the gravity correction starts to. Where a weighing result has legal or commercial consequence, use an instrument verified for the location and the trade in question.
Published the Force Converter: newtons, kilonewtons, kilogram-force, gram-force, pound-force, ounce-force, kip, poundal, dyne and all three tons-force.
Separates mass from force rather than listing kilograms alongside newtons, because a load chart marked kg means kilogram-force while a parcel marked kg means mass, and the two are different quantities.
Bridges mass to force only through an explicitly stated gravity, and returns nothing without one -- an assumed standard gravity would answer every question and be silently wrong about every location.
States that every conversion factor here is exact rather than measured: the pound has been exactly 0.45359237 kg since 1959 and standard gravity exactly 9.80665 metres per second squared since 1901, so the pound-force is exactly 4.4482216152605 newtons.
Explains the constant 32.174 that appears in engineering formulae without justification: it is standard gravity expressed in feet per second squared, and it is the price of using the pound as a mass and as a force in the same equation.
Sets out the two self-consistent imperial systems that need no constant at all -- pound-mass with poundals, and slugs with pound-force -- and shows the slug is 32.174 pounds for the same reason.
Lists the three tons-force apart rather than merging them: short is 2000 pound-force, metric is 1000 kilogram-force, long is 2240 pound-force, and the long is exactly 12 percent above the short while sharing its abbreviation.
Shows that standard gravity is a defined conventional value rather than a measurement, and that real gravity spans 0.71 percent across the inhabited world -- so a spring scale calibrated in London reads about 0.4 kg light on 100 kg in Singapore.
Names where the mass-force distinction genuinely bites -- torque specifications in kgf-metres, anything leaving Earth, load cells calibrated against dead weights, and mixed-origin structural drawings -- and says plainly that elsewhere it can be left alone.
Verified by 57 automated cases, asserting the exact factors as products of their defining constants rather than as copied decimals, that the three tons-force are three distinct values, and that mass refuses to become force without a positive gravity.
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