Calculate kick impact force from body weight and kick type or from mass, velocity, and contact time, with results in N, lbf, and kgf.
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Kick Force Formula
The kick force calculator estimates average impact force from momentum change over contact time. The main formula is:
F = m*v/t
- F = average kick force, in newtons (N)
- m = striking mass, in kilograms (kg)
- v = impact velocity, in meters per second (m/s)
- t = contact time, in seconds (s)
For the quick estimate mode, the calculator estimates striking mass from body weight:
m = BW*0.161
- m = estimated striking mass of the kicking leg, in kilograms
- BW = body weight, converted to kilograms
- 0.161 = estimated fraction of body mass represented by the striking leg
For the custom inputs mode, you enter the striking mass, impact velocity, and contact time directly. The calculator converts your selected units to kg, m/s, and seconds, then applies the same force formula.
The calculator also converts the result into pounds-force and kilogram-force:
lbf = F*0.224809
kgf = F/9.80665
Kick Type Presets Used for Quick Estimates
In quick estimate mode, the kick type sets the impact velocity and contact time. Your body weight sets the estimated striking mass.
| Kick type | Velocity | Contact time |
|---|---|---|
| Front kick | 10 m/s | 0.020 s |
| Roundhouse kick | 14 m/s | 0.020 s |
| Side kick | 11 m/s | 0.020 s |
| Back kick | 12 m/s | 0.020 s |
| Axe kick | 9 m/s | 0.025 s |
| Casual / everyday kick | 6 m/s | 0.030 s |
| Soccer instep kick on ball | 22 m/s | 0.008 s |
Kick Force Result Ranges
| Force range | General interpretation |
|---|---|
| Under 200 N | Similar to a firm shove or light impact. |
| 200 to 600 N | Comparable to a casual punch or light kick. |
| 600 to 1,500 N | Common range for trained martial-arts kicks. |
| 1,500 to 3,000 N | Strong heavy-bag impact. |
| 3,000 to 5,000 N | Very powerful competition-level impact. |
| Over 5,000 N | Extreme impact estimate, usually requiring high speed and short contact time. |
Example Kick Force Calculations
Example 1: Quick estimate roundhouse kick
You weigh 75 kg and select a roundhouse kick. The calculator estimates striking mass as:
m = 75*0.161 = 12.075 kg
For a roundhouse kick, the preset velocity is 14 m/s and contact time is 0.020 s:
F = 12.075*14/0.020 = 8452.5 N
The estimated kick force is 8,452.5 N.
Example 2: Custom kick force
You enter a striking mass of 12 kg, an impact velocity of 10 m/s, and a contact time of 0.025 s:
F = 12*10/0.025 = 4800 N
The estimated kick force is 4,800 N, which is about 1,079 lbf.
FAQ
Why does contact time change the kick force so much?
Force increases when the same momentum change happens over a shorter time. A kick that stops in 0.01 seconds produces about twice the average force of the same kick stopping in 0.02 seconds, assuming the striking mass and velocity are unchanged.
Is this the exact force of a real kick?
No. It is an estimate of average impact force. Real kick force depends on body mechanics, target stiffness, accuracy, footwear, surface deformation, and how much of the leg’s mass is effectively moving into the target.
What is the difference between newtons, lbf, and kgf?
Newtons are the standard metric unit of force. Pounds-force are commonly used in US customary units. Kilogram-force describes the force equal to the weight of a mass in kilograms under standard gravity. The calculator shows all three so you can compare the result in familiar units.
