Force Unit Converter

Convert between force units including newtons, dynes, pound-force, kilogram-force, kip, and more.

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Understanding Force

What is a Newton?

The newton (N) is the SI unit of force. One newton is defined as the force required to accelerate a mass of one kilogram at a rate of one meter per second squared.

1 N = 1 kg·m/s²

Named after Sir Isaac Newton, who formulated the laws of motion.

Newton's Second Law

Force, mass, and acceleration are related by Newton's famous equation:

F = m × a

Where F is force (newtons), m is mass (kilograms), and a is acceleration (m/s²).

Weight vs Mass

Weight is a force caused by gravity acting on mass. At Earth's surface (standard gravity g = 9.80665 m/s²):

Weight (N) = Mass (kg) × 9.80665

A 1 kg mass weighs approximately 9.807 N on Earth, but would weigh only 1.62 N on the Moon!

Kilogram-force vs Kilogram: A Critical Distinction

Similar to the Calorie/calorie confusion, kilogram and kilogram-force are completely different units:

Kilogram (kg)

Type: Unit of mass (SI base unit)

Measures: Amount of matter in an object

Constant: Same everywhere in the universe

Kilogram-force (kgf)

Type: Unit of force (deprecated)

Measures: Weight of 1 kg at standard gravity

Value: 1 kgf = 9.80665 N (exactly)

Important: The kilogram-force (also called kilopond or kp) is a gravitational unit that's deprecated but still used in some engineering contexts.

Dyne (CGS System)

The dyne is the CGS (centimeter-gram-second) unit of force. One dyne is the force required to accelerate a mass of one gram at a rate of one centimeter per second squared.

1 dyn = 1 g·cm/s² = 10⁻⁵ N

The dyne is tiny: 1 newton equals 100,000 dynes.

Pound-force (lbf)

The pound-force is an imperial/US unit defined as the force exerted by gravity on a one-pound mass at standard Earth gravity.

1 lbf = 4.4482216152605 N (exact)

Not to be confused with the pound (lb), which is a unit of mass. A 1 lb mass weighs 1 lbf on Earth.

Kip

The kip (kilopound-force) is commonly used in structural engineering in the United States.

1 kip = 1,000 lbf = 4,448.222 N ≈ 4.45 kN

Building columns and beams are often rated in kips.

Poundal

The poundal is an absolute unit in the foot-pound-second (FPS) system. Unlike pound-force, the poundal is defined without reference to gravity.

1 pdl = 1 lb·ft/s² = 0.138255 N

One poundal accelerates a one-pound mass at 1 ft/s². The poundal is rarely used today.

Sthene

The sthene (sn) is the MTS (meter-tonne-second) system unit of force.

1 sn = 1 t·m/s² = 1,000 N = 1 kN

The sthene is essentially a kilonewton and is rarely used.

Standard Gravity

Standard gravity (g₀ or gₙ) is defined as exactly 9.80665 m/s² for conversion purposes. This is approximately the gravitational acceleration at Earth's surface (45° latitude, sea level). Actual gravity varies by location:

Equator: 9.78 m/s² (centrifugal effect from Earth's rotation)
Poles: 9.83 m/s² (no centrifugal effect, closer to Earth's center)
Moon: 1.62 m/s² (about 1/6 of Earth's)
Mars: 3.71 m/s² (about 38% of Earth's)

Force in Different Contexts

Structural Engineering

Building loads: Measured in kN or kip (structural weight, live loads, wind, seismic)
Concrete strength: Often in MPa (force per area), but loads in kN
Steel tension: Cables rated in kN or ton-force

Aerospace

Thrust: Jet engines and rockets measured in kN or MN
Lift and drag: Aerodynamic forces in newtons
g-forces: Acceleration expressed as multiples of g (9.81 m/s²)

Automotive

Engine torque: N·m (newton-meters, not a force but torque)
Brake force: Measured in newtons or kN
Crash testing: Impact forces in kN

Physics & Biology

Molecular forces: Piconewtons (pN) for DNA, proteins
Atomic forces: Nanonewtons (nN) in AFM microscopy
Friction: Measured in newtons, depends on normal force and coefficient

Ton-force Variants

Type	Mass Basis	Force at Standard Gravity
Metric ton-force	1,000 kg (tonne)	9,806.65 N = 9.80665 kN
Short ton-force (US)	2,000 lb	8,896.44 N = 8.89644 kN
Long ton-force (UK)	2,240 lb	9,964.02 N = 9.96402 kN

Most Common Conversions

Conversion	Example Result
Dynes to Kilonewtons (dyn to kN)	1,000,000 dyn = 0.001 kN
Kilonewtons to Dynes (kN to dyn)	1 kN = 100,000,000 dyn
Kips to Newtons (kip to N)	1 kip = 4,448.222 N
Newtons to Kips (N to kip)	1,000 N = 0.2248 kip
Ponds to Newtons (p to N)	1 p = 0.00980665 N
Newtons to Ponds (N to p)	1 N = 101.972 p

Quick Reference Cards

SI Base Unit

1 N = 1 kg·m/s²

1 kN = 1,000 N

1 MN = 1,000,000 N

Newton - standard SI force unit

Imperial Units

1 lbf = 4.448 N

1 kip = 4,448 N

1 ozf = 0.278 N

Pound-force and derivatives

Gravitational Units

1 kgf = 9.807 N

1 gf = 0.00981 N

1 kp = 9.807 N (same as kgf)

Based on Earth's gravity

CGS System

1 N = 100,000 dyn

1 dyn = 10⁻⁵ N

1 sn = 1 kN

Centimeter-gram-second units

Real-World Force Examples

Weight of Apple

≈ 1 N

≈ 0.102 kgf

Mass of 102 g at Earth's surface

Human Hand Grip

≈ 300-500 N

≈ 67-112 lbf

Average adult grip strength

Car Weight

≈ 15,000 N

≈ 15 kN

1,500 kg car at Earth's gravity

Jet Engine Thrust

≈ 100-500 kN

≈ 22-112 kip

Commercial airliner per engine

Rocket Thrust

≈ 35 MN

≈ 7.9M lbf

Saturn V first stage (5 engines)

DNA Molecular Force

≈ 100 pN

≈ 10⁻¹⁰ N

Force to unzip DNA double helix

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