Force Converter
Convert any force between 11 metric and imperial units in one step. Enter a value, choose its unit, and instantly read the equivalent in newtons, kilonewtons, meganewtons, pound-force, kip, poundal, ounce-force, dyne, kilogram-force, ton-force and sthene. Toggle the Newton's Second Law mode to find force from mass and acceleration.
Formula
Worked example
A 150 lbf bolt preload converts to 667.23 N (0.6672 kN, 68.04 kgf, 0.075 kip, 0.0750 tnf). F = ma: a 10 kg mass at 9.80665 m/s² (1 g) exerts 98.0665 N = 22.05 lbf = 10 kgf.
How force conversion works
Every unit in this tool is defined as a fixed number of newtons, so conversion is a two-step process: multiply your input by the newtons in that unit to reach the SI base, then divide by the newtons in the target unit. The newton itself is a derived unit from Newton's Second Law: one newton accelerates one kilogram at one metre per second squared, giving it the dimensions kilogram-metre per second squared. Routing every value through this single base keeps results mutually consistent and avoids rounding drift from chained unit-to-unit shortcuts. The calculator supports 11 units spanning the SI system (N, kN, MN), the foot-pound-second system (lbf, kip, ozf, pdl, tnf), the CGS system (dyne), the gravitational metric system (kgf) and the MTS system (sthene).
Gravitational units and standard gravity
Pound-force and kilogram-force are gravitational units: they express the force that standard gravity exerts on a given mass. The conversion depends on the agreed value of standard gravity, 9.80665 metres per second squared. A kilogram-force is one kilogram under that acceleration, giving exactly 9.80665 newtons. A pound-force is the avoirdupois pound (0.45359237 kg) under the same gravity, giving 4.4482216152605 newtons. A kip (kilopound-force) is simply 1,000 lbf, used routinely in US structural engineering for bridge and building loads. One short ton-force is 2,000 lbf. The ounce-force is one sixteenth of a pound-force, useful for small tensions such as fishing line or strain-gauge calibration.
Foot-pound-second units: poundal and kip
The poundal (pdl) is the "absolute" force unit of the foot-pound-second system, analogous to the newton in SI. One poundal accelerates one pound-mass at one foot per second squared. Because one foot is 0.3048 m and one pound is 0.45359237 kg, one poundal equals 0.138254954376 N. The poundal appears in older British and American engineering texts and in some fluid-mechanics references. The kip is simply 1,000 pound-force; most US structural codes (AISC, ACI) express loads in kips and moments in kip-feet or kip-inches.
CGS dyne, MTS sthene and other small-system units
The dyne belongs to the centimetre-gram-second system: one dyne accelerates one gram at one centimetre per second squared, making it 1e-5 N. It is still used in surface-tension measurements (dynes per centimetre) and some polymer-physics contexts. The sthene is the force unit of the metre-tonne-second system: 1 sn = 1,000 N. It is rarely used today but appears in some French engineering standards. The meganewton (1 MN = 1,000,000 N) is common in large-scale civil engineering, for example the thrust of a satellite launch vehicle or the bearing capacity of a pile group.
Newton's Second Law mode (F = ma)
Toggle to F = ma mode to compute force directly from mass and acceleration without first knowing the force in any unit. Enter the mass in kilograms, grams, pounds, ounces or tonnes, and the acceleration in m/s², ft/s² or g (standard gravity). The calculator converts both to SI, multiplies them to get newtons, then converts the result into all 11 output units. This is useful for quick checks in mechanics problems: how many newtons does a 5 kg brake caliper piston exert at 6 g deceleration, or how many kips does a 20-ton beam exert at 0.5 g seismic acceleration.
Force units quick-reference table
| Unit | Symbol | System | Newtons (exact or 10 sig. figs) | Typical use |
|---|---|---|---|---|
| Dyne | dyn | CGS | 0.00001 (exact) | Surface tension, polymer physics |
| Newton | N | SI | 1 (exact) | General science and engineering |
| Poundal | pdl | FPS absolute | 0.1382549544 | Old British/US engineering texts |
| Ounce-force | ozf | Gravitational | 0.2780138510 | Small tensions, fishing line, gauges |
| Pound-force | lbf | Gravitational | 4.4482216153 | Everyday US/UK engineering |
| Kilogram-force | kgf | Gravitational | 9.80665 (exact) | Pressure gauges, springs |
| Kilonewton | kN | SI | 1,000 (exact) | Structural loads, vehicles |
| Kip | kip | Gravitational | 4,448.2216153 | US structural engineering (AISC) |
| Sthene | sn | MTS | 1,000 (exact) | Rare; some French standards |
| Ton-force (short) | tnf | Gravitational | 8,896.4432305 | Heavy civil engineering, cranes |
| Meganewton | MN | SI | 1,000,000 (exact) | Rocket thrust, large structures |
Exact or high-precision newton equivalents. Values in bold are exact by definition.
Frequently asked questions
How many newtons are in a pound-force?
One pound-force equals 4.4482216152605 newtons exactly. It is defined as the avoirdupois pound (0.45359237 kg) times standard gravity (9.80665 m/s²). To convert lbf to N, multiply by 4.44822; to convert N to lbf, divide by the same factor. A quick rule of thumb: divide newtons by 4.448 for a rough pound-force equivalent.
What is the difference between kilogram-force and newtons?
A kilogram-force (kgf) is the weight of one kilogram under standard gravity, so 1 kgf = 9.80665 N. It is a force, not a mass. The newton is the SI unit and is independent of gravity, which is why engineers prefer it for unambiguous calculations. Pressure gauges in Europe often display kgf/cm², so knowing 1 kgf = 9.80665 N lets you convert to pascals.
What is a kip in engineering?
A kip is 1,000 pound-force (4,448.22 N). The name blends "kilo" and "pound". US structural engineers routinely express column loads in kips, beam moments in kip-feet, and bolt pretensions in kips. AISC steel design tables and ACI concrete codes both use kips as the standard force unit.
What is a poundal and when is it used?
The poundal (pdl) is the absolute unit of force in the foot-pound-second system: one poundal accelerates one pound-mass at one foot per second squared. It equals 0.138255 N, about one-seventh of an ounce-force. Poundals appear in some older British and American engineering and physics textbooks, and in certain fluid-mechanics derivations. Modern practice generally replaces them with newtons.
Why is a dyne so much smaller than a newton?
The dyne belongs to the centimetre-gram-second system. One dyne accelerates one gram at one centimetre per second squared. Because the metre is 100 times a centimetre and the kilogram is 1,000 times a gram, one newton equals 100 × 1,000 = 100,000 dynes. The dyne is still used for surface tension (dynes per centimetre) and some microscale force measurements.
How do I use F = ma to find force?
Switch the Mode selector to "F = ma". Enter the mass and its unit (kg, g, lb, oz or tonne) and the acceleration and its unit (m/s², ft/s² or g). The calculator converts both to SI, multiplies mass in kg by acceleration in m/s² to get newtons, then converts to all 11 output units. For example, 5 kg at 9.80665 m/s² (1 g) gives 49.03 N = 11.02 lbf = 5 kgf.
How do I convert between ton-force and kilonewtons?
One short ton-force (2,000 lbf) equals 8,896.44 N or 8.89644 kN. To convert tnf to kN, multiply by 8.89644. To go the other way, divide kN by 8.89644. The metric tonne-force (not included here) would be 9.80665 kN, slightly different because it uses 1,000 kg rather than 2,000 lb.